Benchmark DAC2 D Instruction Manual

Benchmark DAC2 D

Instruction Manual

Reference Stereo Preamplifier

PCM and DSD D/A Converter

Asynchronous USB

ESS9018 Conversion System

(Version 2.X Firmware)

Safety Information

Fuses

CAUTION: FOR CONTINUED FIRE

HAZARD PROTECTION ALWAYS REPLACE
THE FUSES WITH THE CORRECT SIZE
AND TYPE (0.5A 250 V SLO-BLO® 5 X 20
MM – LITTELFUSE® HXP218.500 OR
EQUIVALENT). THE FUSE DRAWER
INCLUDES TWO FUSES. ALWAYS
REPLACE BOTH FUSES AT THE SAME
TIME.

AC Input Voltage Range

NOTE: THE DAC2 IS EQUIPPED WITH A

UNIVERSAL POWER SUPPLY. THERE IS
NO VOLTAGE SELECTION SWITCH. AC
VOLTAGE RANGE IS 88-264 VAC, 50-60
HZ. THE PRODUCT MAY ALSO BE
OPERATED FROM DC POWER OVER A
VOLTAGE RANGE OF 125-373 VDC.

Power Cord

CAUTION: ALWAYS USE A GROUNDED

POWER CORD. THE PRODUCT IS
EQUIPPED WITH A STANDARD IEC
POWER ENTRY MODULE. USE AN IEC
POWER CORD THAT IS EQUIPPED WITH
THE APPROPRIATE CONNECTOR FOR
YOUR LOCATION. CORDS ARE AVAILABLE
FROM YOUR DEALER.

Modifications

CAUTION: DO NOT SUBSTITUTE PARTS

OR MAKE ANY MODIFICATIONS
WITHOUT THE WRITTEN APPROVAL OF
BENCHMARK MEDIA SYSTEMS, INC.
MODIFICATION MAY CREATE SAFETY
HAZARDS AND VOID THE WARRANTY.

CAUTION: CHANGES OR MODIFICATIONS

NOT EXPRESSLY APPROVED BY
BENCHMARK MEDIA SYSTEMS COULD
VOID THE USER'S AUTHORITY TO
OPERATE THE EQUIPMENT UNDER FCC
REGULATIONS.

Repairs

CAUTION: DO NOT SERVICE OR REPAIR

THIS PRODUCT UNLESS PROPERLY
QUALIFIED. ONLY A QUALIFIED
TECHNICIAN SHOULD PERFORM
REPAIRS.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 2

Contents

Safety Information 2

Fuses 2
AC Input Voltage Range 2
Power Cord 2
Modifications 2
Repairs 2

Features 4

Introduction 5

Applications 5

DAC2 vs. DAC1 5
DAC2 Technologies 5

Front Panel 8

Rear Panel 8

Quick Start Guide 9

Audio Inputs 9
Remote Control 9
Front Panel Controls 10
Front Panel Displays 11
Headphone Jacks 13

Operational Details 14

DIM and MUTE Functions 14
Auto-On Function 14
HT Mode 15
Preamp COMPATIBILITY Mode 16
USB MODE Selection 16
Driving Power Amplifiers 17
HPA2™ Headphone Amplifier 17
Digital Pass-Through 18
Firmware Version Identification 19

Rear Panel 20

Inputs 20
Outputs 23
AC Power-Entry and Fuse Module 24

Internal Settings 25

Jumper-Configured Options 25
Removing Top Cover 25
XLR Output Pads 25
Headphone Switch Configuration 26
Headphone Amplifier Gain 27
Digital PASS-THROUGH Function 28

Rack Mounting 29

Benchmark Rack Mount Tray 29
Benchmark ½-Wide Blank Plate 29

DAC1, DAC2 Family History 30

DAC1 Series 30
DAC2 Series 30

Benchmark Technologies 32

Hybrid Gain Control™ 32
Native DSD Conversion 32
High Headroom DSP 32
32-bit SABRE-PRO D/A System 35
Diagnostic Displays 35
Distributed Power Regulation 35
HPA2™ Headphone Amplifier 35
Differential Amplifiers 36
Jitter-Immune UltraLock2™ 36
Multi-Mode Asynchronous USB Audio 39

USB Driver Installation 41

Performance Graphs 46

Specifications 62

Audio Performance 62
Group Delay (Latency) 63
Digital Audio Inputs 63
Jitter Tolerance 63
Balanced Analog Outputs 64
Unbalanced Analog Outputs 64

HPA2TM Headphone Outputs 64

Status Display 65
AC Power Requirements 65
Dimensions 65
Weight 65

Regulatory Compliance 66

FCC and RoHS Compliance Statements 66
FCC Notice (U.S. Only) 66
RoHS Compliant Information 66
CE Certificate of Conformity 67

Warranty Information 68

Benchmark 1-Year Warranty 68
Benchmark Extended Warranty Options 69
Notes on Warranty Repairs 69

Manual for DAC2 D with 2.X Firmware - Rev. H Page 3

Features

 HGC™ (Hybrid Gain Control) – combines motor-driven active analog potentiometers, 32-bit

digital attenuators, and passive analog attenuators, to achieve state-of-the-art performance

 Low-Impedance Passive Output Pads – 0, 10, and 20 dB – optimize output level to power

amplifiers and other downstream devices to maximize system SNR (Page 26)

 SABRE PRO - 32-bit PCM D/A conversion system, four 32-bit D/A converters per channel

 SABRE PRO – Native DSD D/A conversion system, four 1-bit DSD D/A converters per channel

 Benchmark UltraLock2™ Jitter Attenuation System – eliminates jitter-induced distortion

 High Headroom DSP - provides 3.5 dB of analog and digital headroom above 0 dBFS to

completely eliminate the clipping of intersample peaks

 Multi-Mode Asynchronous USB Audio 2.0 – 24 bit/192 kHz, DSD (DoP 1.1)

 Driverless Asynchronous USB Audio 1.1 – 24-bit/96 kHz

 Sample Rate Display – displays the measured sample rate, and format (PCM or DSD)

 Word Length Display – displays the measured word length

 HPA2™ reference-grade "0-Ohm" headphone power amplifier with dual high-current

outputs

 HPA2™ gain jumpers for customizing headphone output gain for headphone sensitivities (Page

26)

 2 Headphone Output Jacks – one jack automatically mutes the main outputs , mute feature

can be disabled (Page 26)

 2 Coaxial Digital Inputs – 24-bit/192 kHz PCM, DSD (DoP 1.1)

 2 Optical Digital Inputs – 24-bit/96 kHz PCM

 1 Coaxial Digital Output – digital pass through from USB, Coax, and optical inputs when

function is enabled (Page 28)

 3 Stereo Analog Outputs – 1 pair balanced (XLR), plus 2 pairs unbalanced (RCA)

 IR Remote with metal housing provides control of all functions (optional on some models)

 HT Bypass – sets outputs to calibrated levels - all inputs can be individually programmed

(Page 15)

 Polarity Switch – inverts the polarity of selected digital inputs

 Mute – accessible from remote or front panel

 Dim – Reduces output level by 20 dB, accessible from remote or front panel

 Automatic De-Emphasis – automatically responds to consumer pre-emphasis bit (44.1, 48

kHz)

 AUTO-ON Function - can be programmed to turn on when AC is applied (Page 14)

 Power Switch – very low standby power , <0.5 W at 120 VAC

 High-Efficiency Low-Noise Power Supplies – only 12-15 W, 88-264 VAC, 50-60 Hz

 Meets FCC Class B and CE emissions requirements

 Tested for immunity to radiated and conducted RF interference

Manual for DAC2 D with 2.X Firmware - Rev. H Page 4

Introduction

Applications

The DAC2 D is a professional reference-grade
audio digital to analog converter with
Benchmark's HPA2™ headphone amplifier.
The DAC2 D supports 24-bit D/A conversion
of PCM at sample rates up to 192 kHz. It also
supports direct conversion of 1-bit DSD at a

2.8224 MHz sample rate. It is designed to be
very transparent and this makes it well-suited
for critical monitoring in studio control rooms
and mastering rooms.

The DAC2 D is also well-suited for high-end
hi-fi environments. It includes a generous
collection of inputs and outputs and can serve
as the central component in any stereo hi-fi
system. The DAC2 D provides D/A
conversion, source selection, volume control,
and headphone amplification. A remote
control and a home theater bypass function
provide the features needed in a home
environment.

The DAC2 D is designed to directly drive a
wide variety of power amplifiers and powered
monitors. The balanced outputs include low­impedance passive pads that can be adjusted
to optimize the interface between the DAC2
D and the power amplifier. This optimization
can provide substantial improvements in the
system-level SNR and THD+N performance.

DAC2 Technologies

4:1 Parallel Conversion Structure

The conversion system in the DAC2 achieves
a 6 dB signal to noise improvement through
the use of 4:1 summing. The ES9018 D/A is
an 8-channel 32-bit converter. In the DAC2,
four channels are summed in the analog
domain to form each of the two output
channels.

The 4:1 summing also improves the THD. The
non-linearities in individual conversion
channels are averaged across the four
summed channels and incoherent non­linearities are attenuated by 6 dB.

High-Headroom Digital and Analog
Processing

The DAC2 has generous amounts of analog
and digital headroom. The analog clip point is
above 29 dBu. The digital clip point is 27.5
dBu. When operating at a typical -20 dB at
+4 dBu studio calibration, the DAC2 has 3.5
dB of digital headroom above 0 dBFS. This
digital headroom prevents the clipping of
intersample overs.

DAC2 vs. DAC1

The DAC2 D adds these features that are not
found on the DAC1:

 Asynchronous 192kHz USB Audio 2.0
 32-bit D/A conversion system
 Word Length Display
 Sample Rate Display
 Polarity Control
 Direct DSD D/A Conversion
 -20 dB DIM
 Power Switch with Auto-On Function
 Home Theater Bypass
 Digital Pass-Through
 High-Headroom DSP
 Dual-Domain Hybrid Gain Control
 Additional I/O

No Clipping of Intersample Overs

The DAC2 is one of very few D/A converters
that can accurately reproduce intersample
overs without clipping. Intersample peaks can
reach +3.01 dBFS and commonly occur many
times per second in most 44.1 kHz and 48
kHz recordings. When recordings are ripped
using lossy compression systems (such as
MP3), additional intersample overs are often
created. Most converters (including the
DAC1) produce bursts of distortion at every
occurrence of an intersample over. In
contrast, the DAC2 converters cleanly
reproduce all intersample overs.

Low-Noise Power Supplies

The DAC2 uses high-efficiency low-noise
power supplies. Each critical subsystem also

Manual for DAC2 D with 2.X Firmware - Rev. H Page 5

has at least one dedicated low-noise
regulator. The high-efficiency supplies deliver
the substantial power required by the low­impedance circuits, the headphone amplifier,
and the output line drivers. A power switch is
included. The standby power consumption is
less than 0.5 W when the unit is off.

Low Magnetic Emissions

The magnetic components in the DAC2 power
supplies operate at over 800 kHz. This allows
the use of very small magnetic components
that emit correspondingly small magnetic
fields. This virtually eliminates all traces of
line-frequency components in the output
spectrum of the DAC2. This also means that
the DAC2 can be placed in close proximity to
any audio component without causing
interference with the other component.

UltraLock2™ Clock System

UltraLock2™ provides the outstanding jitter

attenuation.

Dual-Mode USB Input

The DAC2 has a USB input that can be
operated in two modes; driverless USB

Audio 1.1, and a high sample rate USB
Audio 2.0. Both use asynchronous clocking

to eliminate the USB interface as a source of
clock jitter.

Native Asynchronous USB 1.1

The DAC2 has a driverless USB Audio 1.1
mode that supports 96 kHz, 24-bit PCM with
all operating systems. This mode provides a
quick and easy connection to a wide variety of
computers and tablets without installing a
driver.

HGC™ Hybrid Gain Control

HGC™ is Benchmark’s unique hybrid gain

control that combines analog and digital gain
control into a single volume control knob.

The HGC™ system uses an active analog gain
control for analog inputs (if equipped) and a
32-bit dithered volume control for digital
inputs. Both types of inputs leverage the low­impedance passive analog attenuation system
at the XLR outputs.

The dual-domain HGC™ system combines the
high dynamic range of Benchmark’s HDR™
analog control (used in the DAC1 HDR) with
the low distortion and accuracy of a digital
control. HGC™ outperforms traditional analog
or digital volume controls, including the two­stage DAC1 HDR™ system. Musical details
are preserved over a very wide range of
output levels. Analog inputs are controlled in
the analog domain. Digital inputs are
controlled in both domains (32-bit digital
volume plus passive analog attenuators).

Note: To provide full backward and forward

compatibility, the DAC2 uses the DAC2 USB
drivers. This prevents the need to install two
different sets of drivers. Please note that the
DAC2 USB input will be identified as
"Benchmark DAC2" in your computer control
panels.

Asynchronous USB Audio 2.0

The USB Audio 2.0 interface supports DSD
and 192 kHz, 24-bit PCM. No drivers are
required for Apple operating systems. Drivers
are provided for Windows operating systems
at: BenchmarkMedia.com/drivers

Manual for DAC2 D with 2.X Firmware - Rev. H Page 6

The volume control is a servo-driven analog
potentiometer. This control rotates in
response to commands from the remote
control while providing the convenience of
manual adjustments with a physical knob.

Low-Impedance Passive Attenuators

Like the DAC1, the DAC2 includes low­impedance passive attenuators on the XLR
outputs. These attenuators can be adjusted to
optimize the interface with the power
amplifier or powered monitors. This
optimization places the volume control in its
best operating range. This exclusive
Benchmark feature can provide substantial

improvements in the performance of the
playback signal chain.

systems where the DAC2 handles the main
left and right channels.

Native DSD Conversion

The DAC2 supports native DSD conversion.
This feature was not available on the DAC1.
DSD signals can be delivered to the USB or
Coaxial inputs in DoP 1.1 format. The DSD
signal is then routed directly to a bank of 1­bit DSD D/A converters. Four balanced 1-bit
converters are summed together for each
balanced output.

Digital Pass-Through

The second coaxial input (D4) can be
reconfigured as a digital output. When
operating as an output, any selected digital
input is passed through to D4 without any
processing. Optical, coaxial, and USB inputs
can be passed through to the D4 connector.
This even includes special signals such as
DoP, DTS, Dolby Digital, even when these
signals cannot be decoded by the DAC2.

Polarity Control

Auto-On Function

The DAC2 can be programmed to
automatically turn on when AC power is
applied (Page 14).

Each digital input can be inverted, to correct
polarity problems. Some listeners report that
polarity is incorrect on some recordings, and
that they enjoy an improved listening
experience when this is corrected. To toggle,
use the POLARITY button on the front panel
or press and hold the ON button on the
remote.

HT Mode

The HT mode sets the volume control to a
calibrated level that is near its maximum
setting. In HT mode the analog gain is set to
0 dB (unity gain). Likewise the digital
attenuation is set to 0 dB (maximum output).
The HT light is illuminated when the HT mode
is active.

The HT mode is similar to the CALIBRATED
switch setting on the DAC1 except that it is
programmable per input. This flexibility allows
seamless integration into home theater

Manual for DAC2 D with 2.X Firmware - Rev. H Page 7

Front Panel

Rear Panel

Manual for DAC2 D with 2.X Firmware - Rev. H Page 8

Quick Start Guide

OFF

Turns the unit off.

ON

Turns the unit on.

Press and hold the ON button for
3 seconds to toggle the

POLARITY function.

VOLUME

Turns the volume up or down.

DIM

Toggles the -20 dB DIM function.

MUTE

Toggles the MUTE function.

Press and hold the MUTE button
for 3 seconds to toggle the HT
mode on the selected input.

INPUT

Selects the inputs.

D1

Selects optical digital input D1.

D2

Selects optical digital input D2.

D3

Selects coaxial digital input D3.

D4

Selects coaxial digital input D4.

USB

Selects USB input.

Press and hold the USB button for
3 seconds to toggle between the

USB 1.1 and USB 2.0 modes.

Analog

Not used.

Audio Inputs

The DAC2 D features five stereo digital inputs
(2 coaxial, 2 optical, and 1 USB). The coaxial
and optical inputs accept professional (AES)
and consumer (S/PDIF) data formats at word
lengths up to 24-bits.

Tip: We recommend using the coaxial or USB

inputs for sample rates above 96 kHz. Optical
interfaces are not always reliable at sample
rates above 96 kHz.

Remote Control

The remote control is designed to have a long
operating range. In most applications it is not
necessary to point the remote directly at the
DAC2 D.

The chart at the right summarizes the
functions of the IR remote control.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 9

Front Panel Controls

POWER

Turns the unit on or off.

Starting with the unit off, press
and hold the POWER button
for 3 seconds to set the AUTO-
ON function.

Starting with the unit on, press
and hold the POWER button
for 3 seconds to clear the
AUTO-ON function.

If AUTO-ON is set, the

POWER button will toggle
MUTE on and off (the unit will

remain on).

DIM/MUTE

Press once to toggle the -20 dB
DIM function.

Double tap to set the MUTE
function.

Simultaneously hold the
DIM/MUTE and INPUT-UP
buttons for 3 seconds to
activate or deactivate the

COMPATIBILITY mode.

INPUT

Selects the inputs.

Press and hold both input
buttons for 3 seconds to toggle
between the USB 1.1 and USB

2.0 modes.

VOLUME
(knob)

This motor-driven knob can be
turned by hand at any time
(even when being driven by the
motor).

If HT mode is off, the motor
drive will release when the
knob is held or turned by hand.
If HT mode is on, the motor
drive will attempt to return the
volume control to the HT
setting.

The front panel controls duplicate all of the
functions that are available from the remote
control.

Two additional functions, AUTO-ON, and
COMPATIBILITY mode are only controllable
from the front panel.

 The AUTO-ON function keeps the

DAC2 D on whenever AC line voltage
is supplied.

 The COMPATIBILITY mode disables

the volume control when the DAC2 D
feeds a preamplifier that will be used
to control the system playback
volume. mote can be used to control
both devices.

Tip: When AUTO-ON is enabled, a switched

AC outlet can be used to turn your system on
and off.

The chart at the right summarizes the
functions of the front-panel controls.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 10

Front Panel Displays

U

A solid blue light indicates that the USB
input is selected and operating normally.
A blinking blue light indicates that the
input is selected but a connection to a
computer has not been established.

D1

A solid blue light indicates that optical
input D1 is selected and operating
normally. A blinking blue light indicates
that the input is selected but audio data
is not being received.

D2

A solid blue light indicates that optical
input D2 is selected and operating
normally. A blinking blue light indicates
that the input is selected but audio data
is not being received.

D3

A solid blue light indicates that coaxial
input D3 is selected and operating
normally. A blinking blue light indicates
that the input is selected but audio data
is not being received.

D4

A solid blue light indicates that coaxial
input D4 is selected and operating
normally. A blinking blue light indicates
that the input is selected but audio data
is not being received.

Slow Flash

(2Hz)

No digital signal (output
muted)

Med. Flash

(7Hz)

Data transmission errors or
Non-PCM (output muted)

Rapid flashes

(14Hz)

Non-audio data is being
received (output muted)

Intermittent
flashes

Some data corruption is
occurring, converter may be
interpolating to replace
invalid samples, check the
cable.

HT

A solid light indicates that the HT mode
is active on the selected input and the
volume control is in the factory
calibrated position (near full clockwise).
A blinking light indicates that the HT
mode is active but the volume control
has not yet reached its calibrated
position. The HT light and DIM/MUTE
light will blink together if the unit is
muted while HT mode is active.

There are sixteen status indicator lights on
the front panel. At least one light will be
illuminated whenever power is on.

Input Indicators

The input indicators show
which input is selected.

A flashing light indicates an
error on a digital input.

The HT light shows that HT
mode is active.

Input Error Codes

The input indicators flash when errors are
present on the selected digital input. Use the
following table to diagnose the problem:

Tip: Common causes of input errors:

 Disconnected or faulty cable
 Use of excessively long digital cables
 Use of analog cables for digital signals
 Use of optical cables for sample rates

exceeding 96 kHz

 Incompatible data type (AC3, ADAT, etc.)
 Non-audio data is being received

Note: D4 cannot be selected if the Digital

Pass Through function is enabled.

Instructions for configuring this jumper­selected function can be found in the

Internal Settings section of this manual

(Page 28).

Manual for DAC2 D with 2.X Firmware - Rev. H Page 11

HT Indicator

DIM, MUTE, and POLARITY Indicators

DIM/MUTE

A solid red light indicates that
the unit is in DIM mode (-20
dB). A slow flashing red light
indicates that the unit is in
MUTE mode. A rapidly flashing
red light indicates that the
remote control is sending
commands.

POLARITY

Yellow light indicates that the
POLARITY inversion function
is active.

16 Only

Measured input word length is
16 bits.

16 and 24

Measured input word length is
17 to 23 bits.

24 Only

Measured input word length is
24 bits.

Both Off

Measured input word length is
less than 16 bits.

44 Only

The input format is PCM at a
sample rate of 44.1 kHz (CD
sample rate).

48 Only

The input format is PCM at a
sample rate of 48 kHz (often
used with video).

44 and 2X

The input format is PCM at a
sample rate of 88.2 kHz
(high-resolution audio
format).

48 and 2X

The input format is PCM at a
sample rate of 96 kHz (high­resolution audio format).

44 and 4X

The input format is PCM at a
sample rate of 176.4 kHz
(high-resolution audio
format).

48 and 4X

The input format is PCM at a
sample rate of 192 kHz (high­resolution audio format).

DSD

(4x and 2X)

The input format is 1-bit DSD
at a sample rate of 2.8224
MHz (high-resolution audio
format). Note: DSD must be
streamed in DoP format.

All Off

Digital signal is not present or
is not in a supported format.

Word Length Indicators

The 16 and 24 lights indicate the measured
word length of the selected digital input. The
DAC2 D detects active data bits and displays
the results as follows:

Format indicators

The 44, 48, 2X, 4X, and DSD lights indicate
the sample rate and format of the selected
digital input as follows:

Digital Format Indicators

Two lights indicate
the measured word
length of the
selected digital
input.

Four lights indicate
the sample rate and
format of the
selected digital
input.

Tip: Computers, disk players, and streaming

devices often subject the digital signal to
sample rate conversion, changes in word
length, PCM to DSD conversions, and other
forms of digital processing that may degrade
the quality of the audio. This display makes it
easy to detect these processes.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 12

Headphone Jacks

The left-hand jack
mutes the XLR and
RCA outputs.

The right-hand jack
keeps all outputs
active.

Tip: The Volume Control simultaneously

adjusts the level for both jacks. If two
listeners will be simultaneously using the
headphone outputs, we recommend using
headphones with identical or similar voltage
sensitivities.

HPA2TM Headphone Power Amplifier

The headphone jacks are driven by
Benchmark's HPA2™ headphone power
amplifier. This small and very clean power
amplifier can deliver the current and voltage
required by some of the most demanding
headphones. The output impedance of the
HPA2™ is very close to 0 Ohms. This low
output impedance delivers a high damping
factor so that the amplifier can maintain
precise control over the headphone
transducers.

Headphone Mute Switch

The left-hand headphone jack includes a
switch that mutes the main analog outputs
(XLR and RCA) when a headphone plug is
inserted. This feature allows the listener to
switch from loudspeaker to headphone
playback seamlessly. This Auto-Mute feature
can be disabled with internal jumpers.

Note: Instructions for setting the Auto-Mute

jumpers can be found in the Internal

Settings section of this manual (Page 26).

Tip: Use the left-hand jack to mute your

loudspeaker system. Use the right-hand jack
to keep all outputs active.

Headphone voltage sensitivities vary
substantially, so we have equipped the
HPA2™ with Gain-Range jumpers that can
be used to customize the headphone amplifier
to your favorite headphones. If you find that
you have too much output (volume control
set below 11 o'clock), there are internal
jumpers that can be adjusted to decrease the
output level by 10 dB or 20 dB relative to the
factory default setting.

Note: Instructions for setting the headphone

Gain-Range jumpers can be found in the

Internal Settings section of this manual

(Page 26).

Tip: For optimal performance, the headphone

Gain-Range jumpers should be set so that

comfortable listening levels occur when the
volume control is set above the 11 o'clock
position.

Driving Two Sets of Headphones

The HPA2™ is specifically designed with
enough power to drive two sets of
headphones.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 13

Operational Details

DIM and MUTE Functions

activated, the DIM mode will automatically
deactivate, the DIM light will turn off, and the
saved NORMAL setting will be replaced by
the current volume setting.

Definition: If the DIM, MUTE, HT and

COMPATIBILITY modes are all off, the
DAC2 D is in NORMAL mode.

Definition: The NORMAL volume setting is

the last volume setting that was in use before
the DIM, MUTE, HT or COMPATIBILITY
modes were activated.

DIM Function

The DIM function reduces the output level by
20 dB. To toggle between NORMAL and DIM
volume, press the DIM button on the remote
or the DIM/MUTE button on the front panel.

The red DIM/MUTE light will turn on
whenever DIM is active.

When DIM is activated, the NORMAL volume
setting is stored in memory while the volume
control ramps down by 20 dB. When DIM is
deactivated, the volume control ramps back
to the NORMAL volume setting that was
stored in memory.

The DIM function makes it convenient to fade
back and forth between normal and
background playback volume levels.

TIP: In the studio, the DIM function allows a

temporary reduction in level without losing
the volume setting that was being used for
monitoring.

DIM cannot be activated when HT mode is
enabled.

With digital inputs, DIM will reduce the
output level by exactly 20 dB.

MUTE Function

The MUTE function immediately mutes all
outputs. To toggle this function, press the
MUTE button on the remote or double-tap
the DIM/MUTE button on the front panel.

The red DIM/MUTE light will flash at a 1 Hz
rate whenever MUTE is active.

When MUTE is activated from a NORMAL
listening mode, the audio will immediately
mute while the motor-driven volume control
ramps down to the -20 dB DIM position.
When MUTE is released, the output will
unmute at the DIM volume position and then
ramp back up to the previous setting. This
movement of the motor-driven volume
control provides a soft unmute when MUTE is
released. It also allows immediate transitions
between MUTE and DIM.

Tip: If the unit is in MUTE, press the DIM

key to immediately enter the DIM mode.

Tip: If the unit is in MUTE, press the ON key

to enter the NORMAL mode.

Tip: In home applications the DIM function

allows temporary reductions in volume during
TV commercial breaks, phone calls, or other
interruptions, without losing the volume
setting that was being used for normal
listening.

If the volume is adjusted while DIM is active,
it will not change the NORMAL setting unless
the DIM volume is turned up above the last
NORMAL setting. If the volume control is
turned up by more than 20 dB after DIM is

Manual for DAC2 D with 2.X Firmware - Rev. H Page 14

Tip: if the unit is in DIM, press the MUTE

key to toggle between DIM and MUTE.

Auto-On Function

The DAC2 D can be programmed to
automatically turn on whenever AC power is
applied. This function allows automation using
switched AC outlets. When AUTO-ON is
enabled, the DAC2 D cannot be turned off
without removing AC power.

The AUTO-ON function is programmed by
pressing and holding the POWER button on
the front panel for three seconds. This
function cannot be programmed from the
remote control. This limitation prevents
accidental access to this special feature.

Enabling AUTO-ON

Starting with the DAC2 D off, press and hold
the POWER button for 3 seconds.

If AUTO-ON has been successfully enabled,
the unit cannot be turned off using the
POWER button or the OFF button on the
remote. These buttons will place the unit in
MUTE unless the COMPATIBILITY MODE is
also enabled. These buttons will have no
function when the COMPATIBILITY MODE is
also enabled.

Disabling AUTO-ON

Starting with the DAC2 D on, press and hold
the POWER button for 3 seconds. At the end
of 3 seconds the DAC2 D will power down if
the AUTO-ON mode has been successfully
disabled.

HT Mode

The HT mode sets the volume control to a
calibrated level that is near its maximum
setting.

measured at the XLR outputs, and 2 Vrms
measured at the RCA outputs. The HT light is
illuminated when the HT mode is active.

Enabling the HT mode:

Each input channel can be programmed
individually by pressing and holding the
MUTE button for three seconds. The HT
mode is similar to the CALIBRATED switch
setting on the DAC1 except that the HT
mode can be programmable separately for
each input. This flexibility allows seamless
integration into home theater systems where
the DAC2 D handles the main left and right
channels.

HT Mode - Volume Control Bypass

The HT mode is useful whenever the system
volume will be controlled before or after the
DAC2 D. It is usually best to avoid having
two cascaded volume controls in a playback
system. Dual controls will usually degrade the
noise performance of the system and they
can lead to confusion.

Tip: If the DAC2 D feeds a preamplifier, the

HT mode would need to be turned on

individually for each input. Consider using the

COMPATIBILITY mode instead. The
COMPATIBILITY mode places all inputs into

the HT mode while also disabling the MUTE
and DIM controls.

The HT mode has three distinct applications:

 Volume Control Bypass - useful

when the system has an upstream
digital volume control or a downstream
analog volume control

 Home Theater Bypass - allows high-

quality stereo playback on a system
that is also used for surround
applications

 Calibrated Output - useful in studio

applications where calibrated levels
are needed

In HT mode the analog outputs are calibrated
to +24 dBu at 0 dBFS (+4 dBu at -20 dBFS)

Manual for DAC2 D with 2.X Firmware - Rev. H Page 15

If the DAC2 D is directly feeding an amplifier,
but one or more sources have volume
controls, the sources with volume controls
can be set to HT mode.

Example: The USB input is fed from a
computer that has an internal digital volume
control. If you wish to use the volume control
in the computer exclusively, you will want to
program the USB input with the HT mode on.
All other inputs will have the HT mode turned
off. If you do not wish to use the computer
volume control, leave the HT mode off and
disable the computer volume control (or set it
to maximum).

HT Mode – Calibrated Output

Any digital input can be set to the factory­calibrated fixed-gain by turning the HT mode
on. In HT mode, the analog audio outputs are
set to factory calibrated levels. This mode is
useful in studio applications where calibrated
interface levels are used between various
pieces of equipment. (Note: This function is
similar to the calibrated mode on the DAC1.)

 The DAC2 D will not respond to the

DIM, MUTE, VOLUME-UP, VOLUME­DOWN, INPUT-UP, or INPUT­DOWN keys on the IR remote when
COMPATIBILITY mode is enabled.

USB MODE Selection

The DAC2 D supports two USB MODES:

Preamp COMPATIBILITY Mode

This feature was added in Version 2.0. If you
have an older version, an update is available.

The COMPATIBILITY mode disables the
volume control when the DAC2 D feeds a
preamplifier that will be used to control the
system playback volume. When this mode is
used with a Benchmark preamplifier or line
amplifier, such as the HPA4, a single
Benchmark IR remote can be used to control
both devices.

In COMPATIBILITY mode:

 HT mode is on for all inputs
 MUTE is disabled
 DIM is disabled
 Remote INPUT select arrows are

disabled

 The VOLUME knob will be driven to

the unity-gain HT position.

 As a safety feature, manual rotation of

the VOLUME knob will provide a
momentary override of the HT volume
setting. The knob will be driven to the
unity-gain HT position when released.

 USB Audio 1.1 mode - up to 24 bits

at 96 kHz

 USB Audio 2.0 mode - up to 24 bits

at 192 kHz plus DSD in DoP 1.1 format

Caution: Close all USB audio playback

applications before changing the USB MODE.
If an audio application is playing while the
USB MODE is changed, the audio application
may freeze.

Note: The computer and DAC2 D must be

connected and both must be on before the
USB MODE can be changed.

To change the USB MODE, select the USB
(U) input on DAC2 D and then press and hold
the USB button on the remote control for 3
seconds. If a remote control is not available,
simultaneously press and hold both INPUT
buttons on the front panel for 3 seconds.

After holding the button(s) for 3 seconds,
either the 4X lamp or the 2X lamp will flash
once indicating the new USB MODE. A flash
of the 4X lamp indicates that the unit is now
in USB Audio 2.0 mode. A flash of the 2X
lamp indicates that the unit is now in USB

Audio 1.1 mode.

Enabling the COMPATIBILITY mode:

 Simultaneously hold the DIM/MUTE

and INPUT-UP keys for 3 seconds to
activate or deactivate this feature.

 The HT light will be illuminated on all

inputs when COMPATIBILITY mode
is enabled.

 The DIM/MUTE key will be disabled

when COMPATIBILITY mode is
enabled.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 16

Tip: The 4X or 2X lamp will flash once every

time the USB input is selected. This flash
provides a convenient indication of the
current USB MODE.

Tip: Avoid any unnecessary switching

between USB MODES. Rapid switching
between modes can confuse some operating
systems.

Driving Power Amplifiers

The DAC2 D is designed to directly drive
virtually any audio power amplifier or
powered monitor. This direct connection
provides the cleanest and shortest path from
the digital source to the monitor output.

Tip: In most cases, Benchmark does not

recommend placing an audio device between
the DAC2 D and the power amplifier. One
notable exception is the HPA4 line amplifier.
The HPA4 provides stepped relay gain control
with exceedingly low THD and noise. The
HPA4 provides the ultimate analog volume
control and it can operate transparently
between the DAC2 D and a power amplifier.

The RCA and XLR outputs on the DAC2 D
are equipped with low-impedance high­current drivers. These robust outputs are well
equipped to drive a wide variety of input
impedances. The DAC2 D outputs remain
clean when driving amplifiers that present
difficult loads (high input capacitance and/or
low input impedance).

The XLR outputs on the DAC2 D are
equipped with jumper-configured passive low­impedance output pads. These pads can be
set to an attenuation of 0 dB (pad off), 10
dB, or 20 dB. The pads should be used to
match the output level of the DAC2 D to the
input sensitivity of the power amplifier. Most
power amplifiers and powered monitors will
require the use of the 10 dB or 20 dB pads.
Use the 0 dB setting when driving a
Benchmark AHB2 power amplifier.

Tip: The Benchmark AHB2 power amplifier

has a unique low-gain topology that allows it
to accept full studio-level input signals. This
high-level interconnection provides a very
low-noise connection between the DAC2 D
and the AHB2. Set the input SENSITIVITY
switch on the AHB2 to 22 dBu (all the way
down). This places the AHB2 full-power
output point at an input level of 22 dBu. This
level is exactly 2 dB lower than the calibrated
HT output level of the DAC2 D (when the
pads are set to 0 dB). This configuration
optimizes the gain-staging between the DAC2

D and the AHB2 while placing the DAC2 D
volume control in the proper range.

Tip: If you are using a DAC2 D with non-

Benchmark power amplifiers, the XLR pads
should be set so that comfortable listening
levels occur when the VOLUME control is set
above 11 o’clock. This will optimize the gain­staging between the DAC2 D and your power
amplifier.

Tip: Increase the pad setting if a comfortable

listening level is reached at a VOLUME
control setting below the 11 o'clock position.

Tip: Decrease the pad setting if a comfortable

listening level cannot be reached when the
VOLUME control is fully clockwise.

Instructions for setting the XLR pad jumpers
are detailed in the Internal Settings section
of this manual. The DAC2 D is shipped with
the XLR pads disabled (set to 0 dB). No
adjustments will be necessary if you will be
using a Benchmark AHB2 power amplifier.

HPA2™ Headphone Amplifier

The left headphone jack has a mute switch
that mutes all of the analog outputs on the
back of the DAC2 D. The right headphone jack
does not have a mute switch. The audio output
on both jacks is wired in parallel and is driven
by Benchmark's HPA2™ headphone power
amplifier.

The HPA2™ is one of the most transparent
headphone amplifiers available. It also is able
to deliver high current and/or high signal
levels making it well suited for a wide variety
of headphones. The near 0-Ohm output
impedance provides outstanding damping of
headphone drivers. This damping reduces
distortion while maintaining precise control of
the frequency response at the output of the
amplifier.

The HPA2™ has a set of 3-position gain-range
jumpers that can be used to increase or
decrease the gain by 10 dB relative to the
factory calibrated setting.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 17

The jumpers change the gain of the HPA2™
headphone amplifier without changing the
output impedance. This keeps the output
impedance of the HPA2™ constant and very
near 0 Ohms. External attenuators should
never be inserted after a headphone amplifier
as this would change the output impedance
and alter the frequency response of the
headphones.

Proper gain settings are important for
maximizing the SNR of the headphone
monitoring system. With proper settings, the
full performance of the DAC2 D can be
delivered to the headphones for critical
monitoring tasks and for maximum musical
enjoyment.

The digital pass-through can also be used to
provide the following digital signal
conversions:

 Optical to Coaxial
 USB to Coaxial
 Coaxial to Coaxial (buffering)

DoP encapsulated DSD can also be passed
through D4. DSD files on a computer can be
sent in DoP to the USB input on the DAC2 D.
The USB input can be routed to coaxial
output D4. This output can be recorded by
any 24-bit, 176.4 kHz digital recorder with a
coaxial input. The PCM digital recorder can
then be used to play the DSD recordings.

Tip: When the headphone gain jumpers are

set properly, a normal listening level will be
achieved at a VOLUME control setting above
the 11 o'clock position.

Tip: If a normal listening level is achieved

below an 11 o’clock VOLUME setting, the
headphone gain is too high, and the gain
should be decreased.

Tip: If the level is too low at the maximum

VOLUME setting, the headphone gain is too

low, and the gain should be increased.

Digital Pass-Through

The second coaxial input (D4) can be
reconfigured as a digital output. When
operating as an output, any selected digital
input is passed through to D4 without any
processing.

Optical, coaxial, and USB inputs (U, D1, D2
and D3) can be passed through to the D4
connector. The signals are buffered but are
not processed in any way. For this reason,
any data format can be passed through to the
D4 connector, even when these formats
cannot be decoded by the DAC2 D. Surround
formats, such as DTS, Dolby Digital, cannot
be decoded by the DAC2 D, but they can be
passed to a surround system using the digital
pass-through function.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 18

Firmware Version Identification

Digit 1

Digit 2

4

D2 D3

.4

2

D1 D4

.2

1 U

HT

.1

The firmware version is displayed during the
lamp test while the DAC2 D is turning on. At
least one lamp in the INPUT INDICATOR
will flash rapidly while the remaining lamps
will be on. The flashing lamps identify the
firmware version. The values of each lamp
are shown in this chart below.

Add the values of all flashing lamps to
determine the version number. If no lamp
flashes in the second column, the second digit
is a 0.

Example 1: The U lamp is the only lamp that

flashes. The firmware version is 1.0.

Example 2: The U and HT lamps flash. The

firmware version is 1.1.

Example 3: The D1 lamp is the only lamp

that flashes. The firmware version is 2.0.

Example 4: The D1, D4, and HT lamps

flash. The firmware version is 2.3.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 19

Rear Panel

Inputs

There are five stereo inputs on the DAC2 D:

 USB - USB Audio 1.1 or 2.0 Input
 D1 - Optical Digital Input
 D2 - Optical Digital Input
 D3 - Coaxial Digital Input
 D4 - Coaxial Digital Input or Output*

These inputs are selected using the INPUT
buttons on the front-panel or on the remote­control.

* D4 can be jumper-configured as a digital
PASS-THROUGH output. When enabled, the

selected digital input will be routed to the
internal D/A converter and to output D4. The
selected input will be buffered and sent to
output D4 even if the format cannot be
decoded by the DAC2 D.

The USB input has two operating modes:

 USB Audio 1.1 - PCM up to 24-bits at

96 kHz

 USB Audio 2.0 - PCM up to 24-bits at

192 kHz and DSD (DoP 1.1 format)

Caution: The optical inputs (D1 and D2) are

not recommended for DSD or for sample
rates above 96 kHz. Optical connections may
be unreliable at sample rates above 96 kHz.

Tip: The DAC2 D will not decode

multichannel digital formats such as AC3, and
Dolby Digital. The audio will mute and the
INPUT INDICATORS will flash whenever an
incompatible format is connected to the
selected digital input. If the PASS-THROUGH
mode is enabled, these multichannel formats
can be sent to a surround processor using
connector D4 as a digital output.

The digital inputs support PCM stereo
AES/EBU and SPDIF digital formats. Maximum
word length is 24-bits. Maximum sample rate
is 192kHz.

The digital inputs also support DSD stereo at
a sample rate of 2.8224 MHz using DoP 1.1
encapsulation.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 20

Digital Inputs - Overview

All of the digital inputs on the DAC2 D use
Benchmark's UltraLock2™ system to remove
virtually all of the interface jitter. The result is
that all digital inputs deliver identical audio
performance. The USB, optical, and coaxial
digital inputs will all sound identical if they
receive identical data.

Computer Input – USB

The USB Audio 2.0 mode was tested for
compatibility with Windows XP, Vista, 7, and
8 (driver installation is required for these
Windows versions). Beginning with Windows
10, no driver is required. Do not attempt to
install the driver on Windows 10.

The USB Audio 2.0 mode was also tested for
compatibility with Mac OS X starting with
version 10.6 (operation is driverless for all OS
X versions).

The USB input accepts a Type-B male USB
connector. A Type-A to Type-B USB cable is
provided with the DAC2 D. The USB cable
connects the DAC2 D directly to a computer’s
USB output.

The USB input supports 44.1, 48, 88.2, 96,

176.4, and 192 kHz PCM sample rates at
word lengths up to 24-bits. The USB input
also accepts DSD in DoP 1.1 format.

The DAC2 D can be configured as a USB
Audio 1.1 or USB Audio 2.0 device. Press
and hold the USB button on the REMOTE for
three seconds to toggle the USB MODE. If a
remote is not available, simultaneously press
and hold both input buttons on the front
panel for three seconds.

The USB AUDIO 1.1 mode never requires
the installation of a driver. It allows a quick
driverless connection to Windows machines
when playing sample rates of 96 kHz or less.
In this mode, Windows machines can begin
streaming audio within seconds after the
DAC2 D is connected for the first time. No
software or hardware configuration is usually
required.

Optical Digital Inputs - D1 and D2

The optical input connectors (D1 and D2) are
commonly known as TOSLINK connectors.
The TOSLINK optical connectors used on the
DAC2 D are designed to work well at sample
rates up to 96 kHz. Maximum word length is
24-bits. All sample rates between 28 and 96
kHz are supported. The optical inputs may be
unreliable at sample rates above 96 kHz. The
optical inputs will accept professional
AES/EBU data formats or consumer S/PDIF
data formats.

Tip: The optical inputs include dust caps.

Keep these in place if the input is not being
used.

Coaxial Digital Inputs - D3 and D4

The coaxial digital inputs (D3 and D4) use
female RCA connectors. The input impedance
is 75 Ohms. Maximum word length is 24-bits.
All sample rates between 28 and 195 kHz are
supported. The coaxial digital inputs will
accept professional AES/EBU data formats or
consumer S/PDIF data formats. The coaxial
inputs also accept DSD in DoP 1.1 format.

USB Audio 2.0 is required for DSD and for
all PCM sample rates exceeding 96 kHz.
Windows computers require a driver to
support the USB Audio 2.0 mode.

The USB Audio 1.1 mode was tested for
compatibility with Windows XP, Vista, 7, 8
and 10, Mac OS X, and iPads using the 30-pin
to USB Camera Kit. No driver installation is
required for any of these systems when
operating in USB Audio 1.1 mode.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 21

The coaxial digital inputs are DC isolated,
current limited, and diode protected. The RCA
body is bonded directly to the chassis to
prevent currents in the internal ground
system. This direct bonding also maximizes
RF shielding.

Caution: Use 75-Ohm coaxial cables for

digital audio connections D3 and D4. Digital
interfaces require the use of matched
impedances. Do not use 50-Ohm coaxial

cables, twisted pair cables, or any non-coaxial
cables for digital audio. The digital inputs may
not function, or may be unreliable if the
incorrect cable is used.

Note: The Coaxial inputs (D3 and D4) accept

professional or consumer digital audio
formats. The AES3-id and SMPTE 276M
standards specify a 75-Ohm, 1 Vpp,
professional format which is also known as
AES/EBU and is commonly used in video
production facilities. The IEC 609588-3
standard specifies a 75-Ohm, 0.5 Vpp,
consumer format which is also known as
S/PDIF, and is commonly used in hi-fi
equipment. The coaxial inputs are designed to
accept either type of signal.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 22

Outputs

Analog Outputs

The DAC2 D has one pair of balanced XLR
outputs and two pairs of unbalanced RCA
outputs.

configuration is located in the Internal

Settings section of this manual.

Industry-Standard XLR Wiring

 XLR pin 2 = + Audio Out
 XLR pin 3 = - Audio Out
 XLR pin 1 = Cable Shield

Caution: If the balanced XLR outputs are

wired to an unbalanced input (using a special
adapter cable), pin 3 must be left floating.
Shorting pin 3 to ground will increase the
temperature of the output drivers, will
increase power consumption, and may cause
distortion.

The DAC2 D features high-current output
drivers that are capable of driving 300-Ohm
loads without an increase in distortion. They
are also well suited for driving long cables or
high-capacitance loads.

Balanced XLR Analog Line Outputs

The Left and Right balanced outputs use
Neutrik™ gold-pin male XLR jacks. The XLR
shell and pin 1 (ground) are both directly
bonded to the chassis to prevent currents in
the internal ground system. This direct
bonding also maximizes RF shielding.

The XLR outputs have passive attenuators
that allow direct connections to a wide variety
of audio devices without a loss of dynamic
range. The 10 or 20 dB pads are usually
required for direct interfacing to power
amplifiers and powered speakers. The DAC2
D ships with the pads disabled (0 dB setting).
Use the 0 dB setting with the Benchmark
AHB2 power amplifier. A full description of
the output attenuators and instructions for

Unbalanced RCA Analog Outputs

The Left and Right unbalanced outputs use
female RCA jacks. The ground connections
are bonded to chassis ground at the location
where analog ground is bonded to the
chassis. This minimizes the effects of ground
loops caused by AC currents in the cable
shield. The RCA output impedance is very low
(30 Ohms). This makes these outputs well
suited for driving high-capacitance loads
and/or high-capacitance cables.

Caution: Mono summing with an RCA ‘Y’

cable is not recommended as this will cause
high amounts of distortion. Mono summing

with a ‘Y’ cable can be accomplished with the

use of a modified cable by implementing a 1k

Ohm series resistor in each leg of the ‘Y’.

Note: The XLR pads do not have any effect

on the level of the RCA outputs.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 23

AC Power-Entry and Fuse Module

Input Voltage Range

Note: The DAC2 D is equipped with a

universal power supply. There is no voltage
selection switch. AC voltage range is 88-264
VAC, 50-60 Hz.

Fuses

Caution: For continued fire hazard

protection always replace the fuses with
the correct size and type (0.5A 250 V
Slo-Blo® 5 x 20 mm – Littelfuse®
HXP218.500 or equivalent). The fuse
drawer includes two fuses. Always
replace both fuses at the same time.

Power Cord

Note: The AC power input uses a standard

IEC type connector. One USA-compatible
power cord is included with DAC2 D
converters. IEC style power cords in country­specific configurations are available in your
locality.

Caution: Always use a grounded power

cord. The DAC2 D is equipped with a
standard IEC power entry module. Use
an IEC power cord that is equipped with
the appropriate connector for your
location. Cords are available from your
dealer.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 24

Internal Settings

Balanced Output Drive Capability:

Attenuator Output Maximum Loss in dB

Setting (dB) Impedance Cable (ft) at 20 kHz

0 60 680 0.1

10 425 96 0.1

20 135 302 0.1

Unbalanced Output Drive Capability:

Output Maximum Loss in dB

Impedance Cable (ft) at 20 kHz

30 1360 0.1

XLR Output Pads

Jumper-Configured Options

The following functions are jumper
configured:

 XLR Output Pads
 Headphone Mute Switches
 Headphone Gain
 Digital Pass-Through

Removing Top Cover

The DAC2 D cover must be removed to gain
access to the jumpers. Do not attempt to
remove the faceplate or rear panel.

Caution: The DAC2 D contains static

sensitive components. Static discharge may
cause component failures, may affect the
long-term reliability, or may degrade the
audio performance. Use a static control wrist
strap when changing jumper settings.

 Disconnect AC power by unplugging

the power cord at the back of the
DAC2 D.

 Remove the 8 screws holding the

cover (4 on each side).

 Do not remove any screws on the

front, rear, or bottom panels!

 Never remove the power entry safety

cover in the rear corner of the DAC2.

 Always connect a static-control wrist

strap to the chassis before touching
any internal component.

The XLR outputs are equipped with low­impedance passive pads that may be used to
reduce the output levels while preserving the
full dynamic range of the DAC2 D. The DAC2

D ships with the pads disabled (0 dB setting).

Tip: To set the XLR outputs are factory-

preset to deliver professional studio levels.
Most home installations will require the use of
the 10 dB or 20 dB pads.

Tip: Use the factory-default 0 dB setting with

Benchmark's AHB2 power amplifier. When
directly driving most other power amplifiers
(or powered speakers), start with the 10 dB
pad setting. If necessary, change the pads so
that normal listening levels are achieved
when the VOLUME control is between the 11
o’clock and 3 o'clock positions.

When the output pads are enabled, the
output impedance changes slightly, and the
maximum recommended XLR cable length is
reduced as shown in Table 1. The table
assumes a cable capacitance of 32 pF/foot
and a maximum allowable loss of 0.1 dB at 20
kHz.

Table 1 - Cable Drive Capability

Manual for DAC2 D with 2.X Firmware - Rev. H Page 25

XLR Output Pad Jumpers

Four jumpers on four 6-pin headers (P8, P9,
P10, and P11) allow selection of the output

level at the XLR jacks. The jumpers are
properly configured if a normal playback level
is achieved when the VOLUME control is set
above the 11 o'clock position.

requirements are different the HEADPHONE

SWITCH can be defeated.

Headphone Switch Disable

The HEADPHONE SWITCH on the left-hand
headphone jack can be defeated by adding
jumpers at JP1 and JP2.

One pair of 6-pin headers control the
attenuation at each XLR jack as follows:

 0 dB - (Attenuator disabled) – (Jumper

plug between pins 1 and 2 of each
header) - Factory Default

 -10 dB – (Jumper plug between pins 3

and 4 of each header)

 -20 dB – (Jumper plug between pins 5

and 6 of each header)

 HEADPHONE SWITCH enabled (no

jumpers at JP1 or JP2) - Factory Default

 HEADPHONE SWITCH disabled (jumpers

installed at JP1 and JP2)

Figure 2 - Headphone Switch Enabled
(Factory Default)

Figure 1 - Attenuators set to -10 dB

Headphone Switch Configuration

The left-hand headphone jack is equipped
with a switch that will mute the analog
outputs when a headphone plug is inserted.
The right-hand headphone jack does not have
a mute switch. In most cases it is convenient
to have one jack that mutes the outputs and
one that does not mute the outputs. If your

Manual for DAC2 D with 2.X Firmware - Rev. H Page 26

Figure 3 - Headphone Switch Disabled

Headphone Amplifier Gain

The gain range of the HPA2™ can be set
using jumpers JP3 and JP4:

 Gain = 0 dB - see Figure 4
 Gain = - 10 dB - see Figure 5

(Factory Default)

 Gain = - 20 dB - see Figure 6

The jumpers change the gain of the HPA2™
headphone amplifier without changing the
output impedance. This keeps the output
impedance of the HPA2™ constant and very
near 0 Ohms. External attenuators should
never be inserted after a headphone amplifier
as this would change the output impedance
and alter the frequency response of the
headphones.

Proper gain settings are important for
maximizing the SNR of the headphone
monitoring system. With proper settings, the
full performance of the DAC2 D can be
delivered to the headphones for critical
monitoring tasks and for maximum musical
enjoyment.

Tip: When the headphone gain jumpers are

set properly, a normal listening level will be
achieved at a VOLUME control setting above
the 11 o'clock position.

Tip: If a normal listening level is achieved

below an 11 o’clock VOLUME setting, the
headphone gain is too high, and the gain
should be decreased.

Tip: If the level is too low at the maximum

VOLUME setting, the headphone gain is too

low, and the gain should be increased.

Figure 4 - HPA2™ Gain is 0 dB

Manual for DAC2 D with 2.X Firmware - Rev. H Page 27

Figure 5 - HPA2™ Gain is - 10 dB

Figure 7 – Digital PASS-THROUGH
Enabled

Figure 6 - HPA2™ Gain is - 20 dB

Digital PASS-THROUGH Function

The digital PASS-THROUGH function can be
enabled by moving both P14 jumpers toward
the faceplate shown in Figure 7. Once the
jumpers are moved into the position shown in
Figure 7, D4 is configured as a digital audio
output. When the PASS-THROUGH function
is enabled, D4 cannot be selected as an
input. Any other selected digital input will be
routed to both the internal D/A converter and
to output D4. The digital output at D4 is
buffered, but is not processed. Many digital
audio formats can be passed through to D4
(even when these formats cannot be decoded
by the DAC2 D).

By default, D4 functions as a digital input and
the jumpers are set according to Figure 8.

Figure 8 - Digital PASS-THROUGH
Disabled (Factory Default)

Manual for DAC2 D with 2.X Firmware - Rev. H Page 28

Rack Mounting

An optional rack mount tray allows the
mounting of any two ½-wide Benchmark
products in a single rack space. A blank plate
can be added when only one unit is installed
in the rack mount tray.

The Benchmark Rack Mount Tray and
Benchmark ½-Wide Blank Plate are
available from Benchmark.

Benchmark Rack Mount Tray

Benchmark ½-Wide Blank Plate

The Benchmark ½-Wide Blank Plate is a
½-wide 1-RU anodized aluminum panel for
covering an unused slot in the Benchmark
Rack Mount Tray. It is available in black or
silver. The silver panel includes an engraved
Benchmark logo.

The Benchmark Rack Mount Tray mounts
up to two ½-wide Benchmark products in a
single race space. The tray accepts any
combination of ½-wide Benchmark products
(with or without rack-mount type faceplates).

Visit BenchmarkMedia.com for a complete
selection of cable, accessories, and
replacement parts.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 29

DAC1, DAC2 Family History

The pristine audio performance of the award­winning DAC1 made it the ‘Benchmark’ of
stand-alone D/A converters. The DAC1 USB,
DAC1 PRE , and DAC1 HDR added many
features to the basic DAC1 platform.
Benchmark converters are in use in many of
the world's top studios.

 Three Headphone Gain Ranges
 LM4562/LME49860 opamps throughout
 Premium bulkhead-mounted RCA

connectors

In order to provide room for the analog inputs,
we removed the XLR digital input and replaced
it with two additional coaxial digital inputs.

DAC1 HDR

The following is a brief overview of the various
Benchmark DAC1, DAC2 models:

DAC1 Series

DAC1

Benchmark's original DAC1 converter.

The DAC1 features included:

 Three digital inputs
 XLR outputs with passive pads
 RCA outputs
 Analog volume control
 HPA2™ headphone amplifier
 UltraLock™ jitter-attenuation system

DAC1 USB

The DAC1 USB introduced these
improvements:

 AdvancedUSB™ computer input
 Mute switch on the left headphone jack
 Two headphone gain ranges
 High-current LM4562/LME49860 output

stages - designed to drive difficult loads

 Lower output impedances

Benchmark's AdvancedUSB™ computer input
was the first USB audio interface to support 96
kHz audio without the need to install special
drivers.

DAC1 PRE

The DAC1 PRE added these improvements:

 Three coaxial digital inputs

The DAC1 HDR added:

 IR Remote Control
 HDR-VC™ (high dynamic range

volume control).

The HDR-VC™ features a custom-made,
motor-driven Alps potentiometer. The motor­driven control provides the audio performance
of a manual control while adding the
convenience of remote control.

DAC2 Series

DAC2 HGC

The DAC2 HGC maintains the familiar ½-wide
DAC1 form factor, but the entire product was

redesigned from the ground up.

The DAC2 HGC features:

 Four 32-bit converters per channel
 Native 24-bit/192kHz PCM conversion
 Native 64X DSD conversion
 High-headroom digital processing
 UltraLock2™ jitter attenuation
 Multi-mode asynchronous USB audio

input

 Sample rate and word length displays
 Polarity control
 Home theater bypass
 Digital pass-through
 Bi-directional 12V trigger
 Two stereo analog inputs
 Three stereo analog outputs
 Two optical inputs
 High-efficiency low-noise power

supplies

Manual for DAC2 D with 2.X Firmware - Rev. H Page 30

DAC2 L

The DAC2 L is identical to the DAC2 HGC
except that the DAC2 L has no headphone
amplifier.

DAC2 D

The DAC2 D is identical to the DAC2 HGC
except that the DAC2 D has no analog inputs
and no 12V trigger.

DAC2 DX

The DAC2 DX replaced the DAC2 D. The new
model added an XLR digital input and the 12V
trigger. It also added a second output bus so
that one set of outputs could be placed in
calibrated mode while the other was controlled
by the volume knob.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 31

Benchmark Technologies

Hybrid Gain Control™

end of its range, it will not damage the motor.
Also, if the pot is manually overridden, it will
not damage the motor.

HGC™ is Benchmark's unique Hybrid Gain
Control™ system. The DAC2 HGC, DAC2 L,

and DAC2 DX combine active analog gain
control, passive low-impedance attenuators, a
32-bit digital gain control, and a servo-driven
volume control. The DAC2 D only uses the
32-bit digital portion of this control since
there are no analog inputs on the DAC2 D.

All inputs are controlled by the rotary volume
control. This volume control moves in
response to commands from the remote
control. Analog inputs are never converted to
digital, and digital inputs never pass through
an analog potentiometer. Digital inputs are
precisely controlled in the 32-bit DSP system.
The DSP system preserves precise L/R
balance, and precise stereo imaging, while
avoiding any source of noise and distortion.

Benchmark's unique passive output
attenuators provide distortion-free gain
reduction without reducing the dynamic range
of the converter. The attenuators optimize the
gain staging between the DAC2 and the
power amplifier. This optimization is
absolutely essential for maximizing the
dynamic range of the entire playback system.
Much of the success of the DAC1 and DAC2
converters can be attributed to the passive
output attenuators. Musical details can be
obscured by system noise whenever a
preamplifier and power amplifier are
improperly matched. The HGC™ system in
your DAC2 will make full use of your power
amplifier's dynamic range. Experience newly
revealed details in your favorite recordings.

The front-panel volume control is a servo­driven gain control built around a custom­made Alps potentiometer. The custom Alps
pot is equipped with a remote-controllable
motor drive.

This potentiometer is equipped with a clutch
which prevents damage from overriding the
motor drive. If the pot is driven beyond the

Native DSD Conversion

The digital coaxial inputs and the USB Audio

2.0 input on the DAC2 support native DSD

conversion. DoP 1.1 DSD encapsulation is
automatically detected on all digital inputs.
The system seamlessly switches to native
DSD conversion when DoP is detected. DoP

1.1 DSD encapsulation is supported by many
media players. DSD downloads are now
available from several sources.

Visit our website for an up-to-date list of DSD
and PCM high resolution download sites.

High Headroom DSP

All of the digital processing in the DAC2 is
designed with a headroom of 3.5 dB above 0
dBFS. A sinusoid that just reaches the
maximum positive and negative digital codes
has a level of 0 dBFS. If the peaks of the
sinusoid occur between samples, higher
signals can be captured without clipping. For
a pure tone, the maximum intersample peak
that can be represented by a PCM system is
+3.01 dBFS.

Benchmark's high-headroom DSP can handle
intersample peaks without overloading or
clipping. Intersample peaks are cleanly
rendered by the DAC2 and are delivered to
the analog outputs without clipping or
distortion. Very few D/A converters can
make this claim!

In most D/A conversion systems, intersample
peaks cause overloading of the upsampling
interpolators and digital filters that are found
in all sigma-delta converters. When overloads
occur, bursts of non-harmonic distortion are
produced. These bursts of high-frequency
distortion may occur many times per second
and may add a false brightness and
harshness to the sound. This defect impacts
PCM formats but does not impact 1-bit DSD
formats. The absence of intersample clipping

Manual for DAC2 D with 2.X Firmware - Rev. H Page 32

may explain some people's preference for

-1.5

-1

-0.5

0

0.5

1

1.5

Intersample Overs

(1 = Maximum Digital Code)

Analog
Audio

Digital
Samples

-1.5

-1

-0.5

0

0.5

1

1.5

Conventional Interpolation

(Intersample Overs are Clipped)

Analog
Audio

Digital
Samples

-1.5

-1

-0.5

0

0.5

1

1.5

High-Headroom Interpolation

(Intersample Overs are Not Clipped)

Analog
Audio

Digital
Samples

DSD. The DAC2 delivers clean PCM
conversion that meets or exceeds the clarity
of DSD.

detail normally associated with high sample
rates.

Intersample overs are common in low sample
rate (44.1 kHz and 48 kHz) commercial
releases. Due to the mathematics and the
bandwidth of typical input signals,
intersample overs are less of a problem in
high sample rate recordings. The reason for
this is that the worst-case (+3.01 dB)
intersample overs occurs for pure tones that
are exactly 1/4 of the sample rate (as shown
in the figure above). At the 44.1 kHz CD
sample rate, the worst case occurs at 11.025
kHz. It turns out that many recordings have
substantial peaks near this frequency. In
contrast, at a sample rate of 88.2 kHz, the
worst-case intersample overs occur at a
frequency of 22.1 kHz where most musical
sources have insufficient energy to produce
significant intersample overs. The 88.2 kHz
sample rate is still susceptible to intersample
overs, but the magnitude of the worst-case
overs tends to be much lower. For example,
at 1/8th of the sample rate (11.025 kHz), the
maximum intersample peak is about +0.66
dB instead of the 3.01 dB worst case at a
sample rate of 44.1 kHz.

The biggest advantage of higher sample rates
may be the immunity to intersample overs. If
higher sample rates sound better, this
difference may be entirely due to the absence

of DSP overloads caused by intersample
overs. Benchmark's high-headroom DSP
renders low sample rates with the clarity and

Manual for DAC2 D with 2.X Firmware - Rev. H Page 33

PCM systems can accurately capture peaks
that exceed 0 dBFS, but these peaks will
overload the oversampling interpolators in
most delta-sigma D/A converters. The
solution is not to eliminate the interpolation
process; the solution is to build interpolators
with more headroom.

The interpolation process is absolutely
necessary to achieve 24-bit state-of-the art
conversion performance. Unfortunately,
intersample overs cause clipping in most
interpolators. This clipping produces distortion
products that are non-harmonic and non­musical. We believe these broadband
distortion products often add a harshness or
false high-frequency brightness to digital
reproduction. The DAC2 avoids these
problems by maintaining at least 3.5 dB of
headroom in the entire conversion system.
We believe this added headroom is a
groundbreaking improvement.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 34

32-bit SABRE-PRO D/A System

Four balanced 32-bit D/A converters deliver
audio to Benchmark's low-impedance current
to voltage converters. The 4:1 redundancy
reduces noise by 6 dB. The redundancy also
reduces the THD. The conversion system at
the core of the DAC2 is as good as it gets.
The analog circuits that follow the D/A
converter are carefully designed. Benchmark
has leveraged its long history of building
reference analog audio equipment to create
an outstanding output stage.

Diagnostic Displays

Ever wonder why that 192 kHz 24-bit
download on your computer just doesn't
sound right? Your media player or computer
may be downsampling to 44.1 kHz and/or
truncating to 16-bits. Many media players and
computer operating systems apply poor­quality sample rate conversion and/or
truncation. Fortunately these problems can be
eliminated with the selection of a good
frequency-agile media player.

Many disk players also downsample all
sources to 44.1/16. This processing can do
significant damage to the audio quality.

The sample-rate and word-length displays on
the DAC2 confirm the proper operation of
your disk player, media player, and computer.

The DAC2 headphone output is driven by
Benchmark’s signature HPA2™ headphone
power amplifier. This high-current, high­output amplifier has an output impedance
that is nearly 0 Ohms. It is designed to drive
loads as low as 30 Ohms without any increase
in distortion. It also has sufficient amplitude
to drive low-sensitivity 600-Ohm headphones.

The HPA2™ includes current-limiting circuits
that fully protect against damage from short
circuits. This is important because the right
channel of a headphone amplifier will
experience a short whenever a mono phone
plug is inserted into the stereo headphone
jack. Shorts may also occur when a plug is
partially inserted.

"0-Ohm" Output Impedance

Most headphone amplifiers use series
resistors to maintain stability and protect
against short-circuit conditions. These
resistors are usually at least 30 Ohms, and
have a negative impact on performance. A
headphone amplifier with series resistors may
measure very well on a test bench when
driving resistive loads. However, the same
amplifier will measure very poorly when
driving a headphone load. Unfortunately,
most manufacturers do not measure or
specify headphone amplifier performance
when loaded with real headphones. The
measurements use ideal resistive loads. Our
measurements show that headphones do not
behave like resistive loads.

Distributed Power Regulation

To achieve the lowest possible noise, the
DAC2 uses distributed power supply
regulation. Each critical subsystem has at
least one dedicated low-noise voltage
regulator.

We have created a discrete ultra low-noise
regulator for the ES9018 D/A converter. This
Benchmark exclusive feature improves the
noise performance of the already-outstanding
ES9018.

HPA2™ Headphone Amplifier

Manual for DAC2 D with 2.X Firmware - Rev. H Page 35

Headphone Performance

In our tests we have measured substantial
distortion across resistors that are wired in
series with headphones. We have conducted
measurements with a variety of headphones.
In general, distortion increases as headphone
impedance decreases. This distortion can be
eliminated with a properly designed "0-Ohm"
headphone amplifier.

The performance of the HPA2™ does not
change when headphones are driven. THD+N
measurements for no-load, 30-Ohm resistive
loads, 30-Ohm headphone loads, and 600­Ohm headphone loads are virtually identical.

The HPA2™ will substantially improve the
sound of 30 and 60-Ohm headphones. It will
make very noticeable improvements with
600-Ohm headphones.

Differential Amplifiers

Differential amplifiers remove common-mode
distortion components from the D/A converter
outputs. This feature is critical for achieving
low-distortion in down-stream devices.
Benchmark addresses common-mode
distortion so that it will not cause distortion in
power amplifiers and other connected
devices. Common-mode distortion can cause
audible distortion while escaping the scrutiny
of an audio analyzer. The balanced and
unbalanced outputs on the DAC2 deliver very
similar performance.

Many D/A converters omit the differential
amplifiers after the converters. Specifications
usually ignore common-mode distortion. A
balanced signal with high common-mode
distortion can measure just fine when feeding
a precisely balanced input on a high-quality
audio analyzer. However, any imbalance in a
downstream device will expose the common­mode distortion.

Jitter-Immune UltraLock2™

Benchmark's UltraLock2™ clock system is
featured in the DAC2. The DSP processing is
32-bits, DSP headroom is 3.5 dB, sample rate
is 211 kHz, and jitter-induced distortion and
noise is at least 160 dB below the level of the
music - well below the threshold of hearing.
Benchmark's UltraLock2™ system eliminates
all audible jitter artifacts while achieving
instantaneous locking.

The Importance of Eliminating Jitter

Accurate 24-bit audio conversion requires a
very low-jitter conversion clock. Jitter can
very easily turn a 24-bit converter into a 16­bit converter (or worse). There is no point in
buying a 24-bit converter if clock jitter has
not been adequately addressed.

Jitter is present on every digital audio
interface. This type of jitter is known as
‘interface jitter’ and it is present even in the
most carefully designed audio systems.
Interface jitter accumulates as digital signals
travel down a cable from one digital device to
the next. If we measure interface jitter in a
typical system we will find that it is 10 to
10,000 times higher than the maximum
allowable level for accurate 24-bit conversion.
Fortunately, interface jitter has absolutely no
effect on the audio unless it influences the
conversion clock in an analog-to-digital
converter (A/D), the conversion clock in a
digital-to-analog converter (D/A), or the rate
estimator in an asynchronous sample rate
converter (ASRC).

Many converters use a single-stage Phase
Lock Loop (PLL) circuit to derive their
conversion clocks from AES/EBU, wordclock,
or superclock reference signals. Single-stage
PLL circuits provide some jitter attenuation
above 5 kHz but none below 5 kHz.
Unfortunately, digital audio signals often have
their strongest jitter components at 2 kHz.
Consequently, these converters can achieve
their rated performance only when driven
from very low jitter sources and through very
short cables. It is highly unlikely that any
converter with a single-stage PLL can achieve
better than 16 bits of performance in a typical
installation. Specified performance may be
severely degraded in most installations.

Better converters often use a two-stage PLL
circuit to filter out more of the interface jitter.
In theory, a two-stage PLL can remove
enough of the jitter to achieve accurate 24-bit
conversion (and some do). However, not all
two-stage PLL circuits are created equal.
Many two-stage PLLs do not remove enough
of the low-frequency jitter. In addition, two­stage PLL circuits often require several
seconds to lock to an incoming signal. Two­stage PLL circuits may fail to lock when jitter
is too high, or when the reference sample
frequency has drifted.

UltraLock™ converters exceed the jitter
attenuation performance of two-stage PLL
converters while achieving near instantaneous

Manual for DAC2 D with 2.X Firmware - Rev. H Page 36

lock time. They are free from the slow-lock
and no-lock problems that can plague two­stage PLL designs. UltraLock™ converters
have extremely high immunity to interface
jitter under all operating conditions.

The UltraLock™ system is so effective that
no jitter-induced artifacts could be detected
using an Audio Precision System 2 Cascade
test set while the inputs to the DAC2 were
exposed to high levels of interface jitter. The
measurement limits included the ability to
detect artifacts as low as –144 dBFS, but
none could be detected, even while applying
jitter amplitudes as high as 12.75 UI, over a
frequency range of 2 Hz to 200 kHz. Any
AES/EBU signal that can be decoded by the
AES/EBU receiver in the DAC2 will be
reproduced without the addition of any
measurable jitter artifacts.

Benchmark’s UltraLock™ technology
eliminates jitter-induced performance
problems. UltraLock™ technology isolates
the conversion clock from the digital audio
interface clock. Jitter on a D/A digital audio
input, or an A/D reference input can never
have any measurable effect on the conversion
clock of an UltraLock™ converter. In an
UltraLock™ converter, the conversion clock
is never phase-locked to a reference clock.
Instead the converter oversampling-ratio is
varied with extremely high precision to
achieve the proper phase relationship to the
reference clock. The clock isolation of the
UltraLock™ system ensures that interface
jitter can never degrade the quality of the
audio conversion. Specified performance is
consistent and repeatable in any installation
with cables of any quality level!

How does conversion clock jitter degrade
converter performance?

Problem #1: Jitter phase-modulates the

audio signal. This modulation creates
sidebands (unwanted tones) above and below
every tone in the audio signal. Worse yet,
these sidebands are often widely separated
from the tones in the original signal.

Jitter-induced sidebands are not musical in
nature because they are not harmonically
related to the original audio. Furthermore,
these sidebands are poorly masked (easy to
hear) because they can be widely separated
above and below the frequencies of the
original audio tones. In many ways, jitter
induced distortion resembles intermodulation
distortion (IMD). Like IMD, jitter induced
distortion is much more audible than
harmonic distortion, and more audible than
THD measurements would suggest.

Jitter creates ‘new audio’ that is not

harmonically related to the original audio

signal. This ‘new audio’ is unexpected and

unwanted. It can cause a loss of imaging, and
can add a low and mid frequency ‘muddiness’
that was not in the original audio.

Jitter-induced sidebands can be measured
using an FFT analyzer while the converter
plays a pure high-amplitude tone. We
typically use a full-scale 10 kHz test tone to
test for the presence of jitter-induced side
bands (see Graph 15 - JITTER TOLERANCE
FFT). This FFT shows that the DAC2 is free
from any jitter-induced sidebands to a
measurement limit of about -144 dB relative
to the level of the test tone. The graph plots
the output spectrum of the DAC2 when
exposed to 31 different jitter frequencies
ranging from 100 Hz to 100 kHz. All 31
output spectra are identical and are free from
any signs of jitter-induced distortion.

Problem #2: Jitter can severely degrade the
anti-alias filters in an oversampling converter.
This is a little known but easily measurable
effect. Most audio converters operate at high
oversampling ratios. This allows the use of
high-performance digital anti-alias filters in
place of the relatively poor performing analog
anti-alias filters. In theory, digital anti-alias
filters can have extremely sharp cutoff
characteristics, and very few negative effects
on the in-band audio signal. Digital anti-alias
filters are usually designed to achieve at least
100 dB of stop-band attenuation. But, digital
filters are designed using the mathematical
assumption that the time interval between
samples is a constant. Unfortunately, sample

Manual for DAC2 D with 2.X Firmware - Rev. H Page 37

clock jitter in an A/D or D/A varies the
effective time interval between samples. This
variation alters the performance of these
carefully designed filters. Small amounts of
jitter can severely degrade stop-band
performance, and can render these filters
useless for preventing aliasing.

The obvious function of a digital anti-alias
filter is the removal of audio tones that are
too high in frequency to be represented at the
selected sample rate. The not-so-obvious
function is the removal of high-frequency
signals that originate inside the converter
box, or even originate inside the converter IC.
These high-frequency signals are a result of
crosstalk between digital and analog signals,
and may have high amplitudes in a poorly
designed system. Under ideal (low jitter)
conditions, the digital anti-alias filter may
remove most of this unwanted noise before it
can alias down into lower (audio) frequencies.
These crosstalk problems may not become
obvious until jitter is present.

Stop-band attenuation can be measured very
easily by sweeping a test tone between 24
kHz and at least 200 kHz while monitoring the
output of the converter.

Is it possible to eliminate all of the
effects of jitter in an entire digital audio
system?

Interface jitter will accumulate throughout

even the most carefully designed digital audio
system. Fortunately, interface jitter can
only degrade digital audio if it affects the
sampling circuit in an analog-to-digital or
digital-to-analog converter. Any attempt to
cure jitter outside of an A/D or D/A will prove
expensive and, at best, will only partially
reduce jitter-induced artifacts. Dedicated
clock signals (word clock, and super clock,
etc.) are often distributed to A/D converters
and D/A converters in an attempt to reduce
jitter. Again, these are only partial solutions
because jitter even accumulates in these
clock distribution systems. Furthermore, a
poor quality master clock generator can
degrade the performance of the entire system
(if converter performance is dependent upon
reference clock quality). Jitter-free A/D and
D/A converters are the only true insurance
against the ill effects of jitter. UltraLock™
converters are jitter-immune under all
operating conditions (they will never add
audible jitter-induced artifacts to an audio
signal).

Put UltraLock™ converters to the test:

We encourage our customers to perform the
above tests on UltraLock™ converters (or let
your ears be the judge). There will be
absolutely no change in performance as jitter
is added to any digital input on an
UltraLock™ converter. Try the same tests on
any converter using conventional single or
two-stage PLL circuits. Tests should be
performed with varying levels of jitter and
with varying jitter frequencies. The results will
be very enlightening. Jitter related problems
have audible (and measurable) effects on A/D
and D/A devices. Practitioners of Digital Audio
need to understand these effects.

What UltraLock™ converters cannot do:

UltraLock™ converters cannot undo damage
that has already been done. If an A/D with a
jitter problem was used to create a digital
audio signal, then there is nothing that can be
done to remove the jitter-induced distortion
that happened inside the A/D converter.
Jitter-induced sidebands are extremely
complex and cannot be removed with any
existing audio device. Therefore, it is very
important to attack jitter at both ends of the
audio chain. The DAC2 is a great start, as it
will allow accurate assessment of various A/D
converters. It is impossible to audibly
evaluate A/D performance without a good
D/A. The consistent performance delivered by
the DAC2 eliminates one major variable ­jitter.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 38

Multi-Mode Asynchronous USB
Audio

Plug it in and Start Listening…

Immediately

Benchmark's Advanced USB Audio system
supports the industry standard USB Audio

1.1 and USB Audio 2.0 protocols. These
audio protocols should not be confused with
USB port speeds. The USB Audio 1.1
protocol requires at least a USB 1.0 (Full
Speed) port. USB Audio 2.0 requires at least
a USB 2.0 (High Speed) port.

Benchmark's USB Audio 1.1 and USB Audio

2.0 modes are frequency agile. This means
that the sample rate is controlled by the
computer. The DAC2 will follow sample rate
changes initiated by the computer and/or the
media playback software.

Tip: The USB Audio 1.1 protocol will run on

any USB port, but if it is run on a USB 1.0
(Full Speed) port, it will require all of the
available bandwidth to support 96 kHz sample
rates. If a USB 1.0 port is the fastest port
available, make sure that there are no other
devices sharing the USB hub that services the
port. When possible, connect the DAC2 to a
port that supports USB 2.0 or higher.

Tip: The USB Audio 2.0 protocol is required

for sample rates above 96 kHz. This protocol
will not run on USB 1.0 ports. When possible,
connect the DAC2 to a port that supports
USB 2.0 or higher.

The DAC2 has a low-jitter master clock which
controls the transfer of audio data from the
computer to the USB sub-system. The
computer asynchronously transfers audio data
to a buffer in the DAC2. The contents of the
buffer are then asynchronously transferred to
the D/A conversion sub-system. This second
asynchronous transfer eliminates any traces
of jitter that accumulate as the data is
transferred between the USB and conversion
subsystems. No traces of jitter-induced
distortion are detectable at our measurement
limits (about -144 dBFS). This truly
represents the state-of-the art. Enjoy the
convenience of computer playback without
compromise.

The Asynchronous USB system supports USB
Audio 2.0 for high-resolution 192kHz, and
DSD playback. No drivers are required for
MAC operating systems. An easy-to-install
driver adds 192 kHz and DSD capabilities to
Windows operating systems.

The asynchronous driverless USB Audio 1.1
mode supports sample rates up to 96 kHz.
This USB mode can be selected from the front
panel or from the remote control. The
driverless USB Audio 1.1 mode allows quick
plug-and-play connections to Windows, MAC,
iOS, and Linux operating systems without
installing drivers. Just plug in the USB, and
the DAC2 becomes an available audio device.
In many cases, audio will automatically be
routed to the newly connected device. If not,
it can be selected as the current or default
playback device.

Asynchronous USB

In all modes the USB communications are
asynchronous. An ultra low jitter conversion
clock is generated inside the DAC2. The
asynchronous USB interface pulls data from
the computer without using computer­generated clocks. The D/A conversion in the
DAC2 is completely isolated by the
asynchronous USB interface and by the
UltraLock2™ jitter-attenuation system.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 39

The industry-standard USB Audio Mode 2.0
mode is natively supported by Windows
operating systems starting with Windows 10.
A driver is required for older Windows
operating systems. The driver supports
Windows XP, Vista, or 7, and 8. This driver is
required for DSD and sample rates above 96
kHz when using these older Windows
systems.

The USB subsystem is computer powered
(through the USB cord) and it remains active
when the DAC2 is powered down. This
feature prevents interruptions to the

computer playback operations and eliminates
the need to reconfigure the computer every
time the converter is turned on.

The Windows USB Audio 2.0 driver is
available at:

BenchmarkMedia.com/drivers

Manual for DAC2 D with 2.X Firmware - Rev. H Page 40

USB Driver Installation

Required for Windows operating systems prior to Windows 10 only!

Note: The DAC2 driver is available for download at: BenchmarkMedia.com/drivers

Before you install the driver, make sure the USB cable is unplugged.

1. In the DAC2 Driver folder, double click “setup.exe.”

Manual for DAC2 D with 2.X Firmware - Rev. H Page 41

2. A welcome screen will pop-up. Click “Next.”

Manual for DAC2 D with 2.X Firmware - Rev. H Page 42

3. When you see the following screen, turn on the DAC2, plug in the USB cable, and select the
USB input on the DAC2. By default, the DAC2 is shipped in USB Audio 1.0 mode. Do not
proceed to the next step until the USB Audio 2.0 mode has been enabled. You can enable
the USB Audio 2.0 mode using one of the following two methods:

 METHOD 1 - REMOTE CONTROL: Using your remote control, press and hold USB

button for 3 seconds (the 4X light should flash once). If the 2X light flashes instead
of the 4X light, repeat this step.

 METHOD 2 - FRONT PANEL: From the front panel, simultaneously press and hold

both INPUT buttons for three seconds (the 4X light should flash once). If the 2X
light flashes instead of the 4X light, repeat this step.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 43

4. You will now be prompted to select a location to install the driver. It will default to your
Program Files folder. If you wish to install it another location, you can change the location.
We suggest keeping it in the default location. Click “Install”.

5. When the installation begins you will see the following screen. Please be patient while the
driver installs. Installation may require several minutes.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 44

6. When the installation finishes a message at the top will say “Installation Complete.” Click
“Next” to continue.

7. Click “Finish.” The Setup will close automatically. This completes the installation process.
You can now enjoy music over the USB Audio 2.0 connection at sample rates up to 192
kHz. DSD can also be played in DoP 1.1 format.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 45

Performance Graphs

Audio Precision

FFT Idle Channel Noise, 0 dBr = 0 dBFS = 23 dBu

DAC2 - FFT Idle Channel Nois e.at27

ColorSweep Trace Line Style Thick Data Axis Com ment

1 1 Green Solid 4 Fft.Ch.1 Ampl L eft
1 2 Red Solid 4 Fft.Ch.2 Ampl R ight

-160

+0

-140

-120

-100

-80

-60

-40

-20

d

B

r

A

-160

+0

-140

-120

-100

-80

-60

-40

-20

d

B

r

A

0 32k2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 22k 24k 26k 28k 30k

Hz

Graph 1 - FFT Idle Channel Noise

The extraordinary performance of the DAC2 is demonstrated by the FFT plot shown above. There
is no sign of any AC hum, there are no idle tones, and there are no spurious tones detected at a
measurement limit of -160 dBFS.

The rise at 0 Hz is normal in an FFT analysis and is not an indication of noise. This 32k point FFT
analysis uses a Blackman-Harris window with 16x power averaging, and spans a frequency range
of DC to 32 kHz.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 46

Audio Precision

FFT Idle Channel Noise - Low Frequency, 0 dBr = 0 dBFS = 23 dBu

DAC2 - FFT Idle Channel Nois e - Low Frequency.at27

ColorSweep Trace L ine Style Thick Data Axis Com men t Curs or1 Curs or2

1 1 Gree n Solid 4 Fft.Ch.1 Ampl Left *-156 .413 dBr *-157.53 9 dBr
1 2 Red Sol id 4 Fft.Ch.2 Ampl Ri ght -159 .813 dBr A -158.700 dBr A

-160

+0

-140

-120

-100

-80

-60

-40

-20

d

B

r

A

-160

+0

-140

-120

-100

-80

-60

-40

-20

-156.413

-157.539

d

B

r

A

25 400 50 75 100 125 150 175 200 225 250 275 300 325 350 375

60.1566 180.626

Hz

dx=120.470 Hz

dy=-1.126 dB

Graph 2 - LOW FREQUENCY FFT - AC LINE-RELATED HUM

The DAC2 shows no evidence of AC line-related hum to a measurement limit of -160 dBFS. The
cursors are placed at 60 Hz and 180 Hz (frequencies where we would expect to see interference
from the 60 Hz AC input. There is absolutely no sign of any AC hum.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 47

Graph 3 - FFT 10 kHz

Audio Precision

DAC2 - FFT 10 kHz, 0 dBr = 0 dBFS = 23 dBu

DAC2 - FFT 10 kHz.at27

ColorSweep Trace Line Style Thick Data Axi s Com ment Cu rsor1 Curs or2

1 1 Green Solid 4 Fft.Ch.1 Ampl L eft *-114.63 6 dBr *-120 .240 dBr
1 2 Red Solid 4 Fft.Ch.2 Ampl R ight -116.765 dBr A -122.816 dBr A

-160

+0

-140

-120

-100

-80

-60

-40

-20

d

B

r

A

-160

+0

-140

-120

-100

-80

-60

-40

-20

-114.636

-120.24

d

B

r

A

0 32k2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 22k 24k 26k 28k 30k

20.0391k 30.0587k

Hz

dx=10.0196 kHz

dy=-5.604 dB

The 10 kHz FFT analysis is an excellent test for detecting sample clock jitter. Jitter will create
sidebands (unwanted tones) above and below the 10 kHz test tone. A jitter frequency of 1 kHz
would create two sideband tones; a lower sideband at 9 kHz, and an upper sideband at 11 kHz.
Similarly, a jitter frequency of 2 kHz would produce sideband tones at 8 kHz and 12 kHz. The
above plot shows no evidence of jitter-induced sidebands to a measurement limit of about -140
dBFS.

The -140 dB measurement limit is due to the SNR limitations of the Audio Precision 2700 test set,
and not the DAC2. Note the very low harmonic distortion; -114 to -116 dB 2nd harmonic (20 kHz),
and -120 to -122 dB 3rd harmonic (30 kHz). Please note that these are almost exactly the same
harmonic distortion levels that occur with a 1 kHz tone (see Graph 4 - FFT 1 kHz). This
demonstrates that the DAC2 analog stages have the high slew rates required to pass high­amplitude high-frequency signals without an increase in harmonic distortion.

The rise at 0 Hz is normal in an FFT analysis and is not an indication of noise. This 32k point FFT
analysis uses a Blackman-Harris window with 16x power averaging, and spans a frequency range
of DC to 32 kHz.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 48

Audio Precision

DAC2 - FFT 1 kHz, 0 dBr = 0 dBFS = 23 dBu

DAC2 - FFT 1 kHz.at27

ColorSweep Trace Line Style Thick D ata Axis Com me nt Curs or1 Curs or2

1 1 Gree n So lid 4 Fft.Ch.1 Ampl Left *-115.26 8 dBr *-1 28.290 dBr
1 2 Red Soli d 4 Fft.Ch.2 Am pl Ri ght -115.95 4 dBr A -130.429 dBr A

-160

+0

-140

-120

-100

-80

-60

-40

-20

d

B

r

A

-160

+0

-140

-120

-100

-80

-60

-40

-20

-115.268

-128.29

d

B

r

A

0 3.2k200 400 600 800 1k 1.2k 1.4k 1.6k 1.8k 2k 2.2k 2.4k 2.6k 2.8k 3k

2.00391k 2.99961k

Hz

dx=.995695 kHz

dy=-13.022 dB

Graph 4 - FFT 1 kHz

The 1 kHz FFT analysis demonstrates the low harmonic distortion of the DAC2. Second harmonic
distortion (2 kHz) measures about -115 dB, while 3rd harmonic distortion measures -128 to -130
dB.

The rise at 0 Hz is normal in an FFT analysis and is not an indication of noise. This 32k point FFT
analysis uses a Blackman-Harris window with 16x power averaging, and spans a frequency range
of DC to 32 kHz.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 49

Graph 5 - FREQUENCY RESPONSE

Audio Precision

10/24/12 16:02:03

DAC2 - FREQUENCY RESPONSE

Fs = 96 kHz

DAC2 - Frequency Respo nse .at27

ColorSweep Trace Line Style Thick D ata Axi s Com me nt Curs or1 C urso r2

1 1 Gree n So lid 4 Anlr.Level A L eft -0.011 dBr A -0.026 dBr A
1 2 Red Soli d 4 Anlr.Level B Rig ht * -0.009 dBr * -0.020 dBr

-10

+1

-9

-8

-7

-6

-5

-4

-3

-2

-1

-0

-0.009-0.02

d

B

r

B

-10

+1

-9

-8

-7

-6

-5

-4

-3

-2

-1

-0

d

B

r

A

5k 45k10k 15k 20k 25k 30k 35k 40k

10.0021 40.4214k

Hz

dx=40.4114 kHz

dy=-0.011 dB

This plot demonstrates the ruler-flat frequency response of the DAC2. Note that the frequency
response measures - 0.01 dB at 10 Hz and -0.02 dB at 40 kHz.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 50

Graph 6 - Differential Phase

Audio Precision

DAC2 - Differential Phase

Fs = 96 kHz

DAC2 - Differential Phas e.at27

ColorSweep Trace Line Style Thick D ata Axis Com ment Curs or1 Curso r2

1 1 Green Solid 4 Anlr.Phase L eft -0.09 deg -0.21 deg
2 1 Red Sol id 4 Anlr.Phase Left * +0.24 deg *+0.47 deg

-1

+1

-0.8

-0.6

-0.4

-0.2

+0

+0.2

+0.4

+0.6

+0.8

+0.24

+0.47

d
e
g

2.5k 45k5k 7.5k 10k 12.5k 15k 17.5k 20k 22.5k 25k 27.5k 30k 32.5k 35k 37.5k 40k 42.5k

20.2555k 40.0511k

Hz

dx=19.7956 kHz

dy=+0.23 deg

This plot demonstrates the inter-channel phase accuracy of the DAC2. From this plot, the inter­channel phase accuracy is calculated to be +/- 0.17 degrees at 20 kHz, and +/- 0.34 degrees at 40
kHz.

The phase accuracy of the DAC2 is almost the same as the phase accuracy of the Audio Precision
2700 test set. For this reason, the phase error in the AP must be subtracted from the
measurement. The green trace assigns the left channel to channel 1 of the AP, and the right
channel to channel 2 of the AP. The red trace reverses the inputs. The two traces must be
averaged to remove the phase errors of the AP test set.

DAC2 converters are phase-accurate between boxes. Three DAC2 converters can be used as a
group to form a phase-accurate 5.1 surround system. Four DAC2 converters can be combined to
form a 7.1 system. The phase accuracy between any two channels will match the phase accuracy
shown above.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 51

Graph 7 - Balanced THD+N vs. Amplitude

Audio Precision

DAC2 - THD+N vs AMPLITUDE AT 1 KHZ (w/20 kHz LPF unweighted)

Balanced Outputs, Relative to 0 dBFS, 0 dBFS = +23 dBu

DAC2 - Balanced THD+N vs AMPLITUDE.at27

ColorSweep Trace Line Style Thick D ata Axis C omm ent

1 1 Green Solid 4 Anlr.THD+N Ampl Left
1 2 Red Sol id 4 Anlr.THD+N Ampl Left

-120

-96

-118

-116

-114

-112

-110

-108

-106

-104

-102

-100

-98

d

B

r

A

-14 -0-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1

dBFS

This plot demonstrates the very low harmonic distortion produced by the DAC2 at signal levels
ranging from -14 dBFS to 0 dBFS. All variations below -4 dBFS are due to the measurement limits
of the AP 2700 system. The peaks at -13 dBFS are due to an AP 2700 gain range change. In
almost all listening environments, THD will be below the threshold of hearing. The DAC2 is virtually
uncolored by any trace of harmonic distortion.

The DAC2 includes differential amplifiers that remove common-mode distortion components. This
is important, because common-mode distortion is not detected when measuring with the precisely­balanced inputs on the AP 2700 test set. The THD+N measurements on the unbalanced outputs
confirm the effectiveness of the differential amplifiers. Similar results are obtained by measuring
either side of the balanced outputs relative to ground.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 52

Graph 8 - Unbalanced THD+N versus Amplitude

Audio Precision

DAC2 - THD+N vs AMPLITUDE AT 1 KHZ (w/20 kHz LPF unweighted)

Unbalanced Outputs, Relative to 0 dBFS, 0 dBFS = +7.2 dBu

DAC2 - Unbalanced THD+N _VS_AMPLITUDE.at27

ColorSweep Trace Li ne Style Thick Data Axis Com ment

1 1 Green Solid 4 Anlr.THD+N Ampl Left
1 2 Red Solid 4 Anlr.THD+N Ampl Left

-120

-95

-119

-118

-117

-116

-115

-114

-113

-112

-111

-110

-109

-108

-107

-106

-105

-104

-103

-102

-101

-100

-99

-98

-97

-96

d
B

r

A

-14 -0-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1

dBFS

This plot shows the THD+N performance of the unbalanced outputs. Note that the THD+N
performance of the unbalanced outputs approaches that of the balanced outputs. The DAC2
includes differential amplifiers that remove common-mode THD from the balanced outputs of the
SABRE converters. These differential amplifiers give the unbalanced outputs the ability to approach
the performance of the balanced outputs. Please note that the differential amplifiers also eliminate
common-mode distortion on the balanced outputs.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 53

Graph 9 - Headphone Amplifier – THD+N versus Amplitude

Audio Precision

DAC2 - THD+N vs AMPLITUDE AT 1 KHZ (w/20 kHz LPF unweighted)

Headphone Outputs, Relative to 0 dBFS, 0 dBFS = +7.2 dBu

DAC2 - HEADPHONE - THD+N_VS_AMPLITUDE.at27

ColorSweep Trace Line Style Thick Data Axi s Com ment

1 1 Green Solid 4 Anlr.THD+N Ampl L eft
1 2 Red Soli d 4 Anlr.THD+N Ampl Left

-104

-86

-102

-100

-98

-96

-94

-92

-90

-88

d

B

r

A

-14 -0-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1

dBFS

This plot shows the THD+N performance of the headphone outputs under load. Note that the
THD+N performance of the headphone outputs approaches that of the balanced outputs. The
DAC2 includes Benchmark's HPA2™ headphone amplifier. The HPA2™ has a near 0-Ohm output
impedance which provides outstanding control and damping of the headphone drivers. The HPA2™
has the voltage and current drive necessary to drive a wide variety of headphones.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 54

Graph 10 - THD+N vs. FREQUENCY 80 kHz

Audio Precision

DAC2 - THD+N VS FREQ AT 0 dBFS (w/80 kHz LPF

unweighted)

Balanced Outputs

DAC2 - THD+N vs FREQUENCY 80kHZ.at27

-110

-90

-107.5

-105

-102.5

-100

-97.5

-95

-92.5

d

B

20 20k 50 100 200 500 1k 2k 5k 10k

Hz

The analog output stages on the DAC2 have high slew rates and are capable of maintaining low
THD levels at high frequencies even when driven to 0 dBFS. Note that there is almost no rise in
THD+N with frequency, even when operating at maximum output levels.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 55

Audio Precision

DAC2 - THD VS FREQ AT 0 dBFS

Balanced Outputs

DAC2 - EVEN AND ODD THD vs FREQUENCY.at27

ColorSwe ep Trace Line Style Thick D ata Axis Com ment Curs or1 Curso r2

1 1 Green So lid 4 Dis tortion.Ch.1 Harm Sum1 Ratio Left *-115 .210 dB *-11 2.066 dB
1 2 Red Solid 4 Distortion .Ch.1 Harm Sum2 Ra tio Righ t -115.165 dB -1 20.544 dB

GREEN = EVEN HARMONIC DISTORTION (2,4,6,8,10,12,14)
RED = ODD HARMONIC DISTORTION (3,5,7,9,11,13,15)

-130

-90

-125

-120

-115

-110

-105

-100

-95

d

B

-130

-90

-125

-120

-115

-110

-105

-100

-95

-115.21

-112.066

d

B

20 10k 50 100 200 500 1k 2k 5k

1.00318k 10k

Hz

dx=8.99682 kHz

dy=+3.144 dB

Graph 11 - EVEN AND ODD THD vs. FREQUENCY

This plot demonstrates that the harmonic distortion of the DAC2 is lower than the THD+N numbers
would suggest. This plot shows THD not THD+N. Even and odd harmonic distortions are plotted
separately. Note that odd harmonics are lower than the more "musical" even harmonics. Both sets
of harmonics are very low in amplitude (-112 dB to -120 dB), and should be entirely inaudible.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 56

Audio Precision

DAC2 - THD VS FREQ AT 0 dBFS

- ALL OUTPUTS

DAC2 - THD vs FREQUENCY.at27

ColorSweep Trace Line Style Thick Da ta Axis C omm ent Source 2 Curs or1

1 2 Blu e Sol id 4 Dis tortion.Ch.1 Harm Sum1 Ratio Left : 1.00000 =Swr.Ch. A+B Input -112.557 dB
1 3 Cyan Solid 4 Distortio n.Ch.2 Harm Sum1 Ratio R ight : 1.00000 =Swr.Ch. A+B Input -1 12.453 dB
2 2 Red Solid 4 Dis tortion.Ch.1 Harm Sum1 Ratio Left : 3.00000 =Swr.Ch. A+B Input -113.919 dB
2 3 Magenta Solid 4 Dis tortion.Ch.2 Harm Sum1 Ra tio Right : 3.00000 =Swr.Ch. A+B Input -113.349 dB
3 2 Green Sol id 4 Dis tortion.Ch.1 Ha rm Sum 1 Ratio Left : 5.00000 =Swr.Ch. A+B Input -117.017 dB
3 3 Yellow Soli d 4 Dis tortion.Ch.2 Harm Sum1 Ratio Right : 5.00000 =Swr.Ch. A+B Input *-114.82 7 dB

1=Balan ced L
2=Balan ced R
3=Unba lanced L
4=Unba lanced R
5=Head phone L
6=Head phone R

-130

-90

-125

-120

-115

-110

-105

-100

-95

-114.827

-106.739

d

B

-130

-90

-125

-120

-115

-110

-105

-100

-95

d

B

20 10k 50 100 200 500 1k 2k 5k

1.00318k 10k

Hz

dx=8.99682 kHz

dy=+8.088 dB

Graph 12 - THD vs. Frequency - All Outputs

This plot demonstrates that all of the analog outputs on the DAC2 have very similar performance
over the entire audio band. The unbalanced outputs, and the headphone outputs, closely match the
performance of the balanced outputs. Like Graph 11, this plot shows THD (not THD+N).

Manual for DAC2 D with 2.X Firmware - Rev. H Page 57

Graph 13 - THD+N versus Sample Rate

Benchmark Media Systems, Inc.

DAC2 - THD+N vs Sample Rate, 1 kHz at 0 dBFS (w/20 kHz LPF unweighted)

Balanced Outputs

DAC2 - THD+N vs Sample Rate.at27

ColorSweep Trace Lin e Style Thick Data Axis C omm ent

1 1 Green Solid 4 Anlr.THD+N Ratio Left
1 2 Red So lid 4 Anlr.THD+N Ra tio Le ft

-120

-90

-117.5

-115

-112.5

-110

-107.5

-105

-102.5

-100

-97.5

-95

-92.5

d

B

40k 200k60k 80k 100k 120k 140k 160k 180k

Hz

The THD+N performance of the DAC2 is identical at all Sample Rates.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 58

Graph 14 - JITTER TOLERANCE

Audio Precision

DAC2 - INTERFACE JITTER TOLERANCE - Distortion vs Jitter

3.456 kHz Test Tone at 0 dBFS, THD+N 22 to 22 kHz BW

DAC2 - JITTER TOLERANCE.at27

ColorSwee p Trace Line Style Thick D ata Axis Co mm ent

1 1 Green Sol id 4 Anlr.THD+N Ratio Left
1 2 Red Solid 4 Dio.Interface Jitter Right

DAC2 THD+N (22-22kHz) (Green Trace) vs. Interface Jitter (Red Trace)
Digital Inpu t = 3.456 kHz Tone at 0 dBFS, Fs = 48 kHz

10m

20

20m

50m

100m

200m

500m

1

2

5

10

U

I

-110

+0

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

d

B

100 90k200 500 1k 2k 5k 10k 20k 50k

Hz

The Audio Engineering Society (AES) has created a jitter tolerance template for testing digital audio
devices. The red curve shows the AES jitter tolerance template. Induced jitter approaches 5 UI at
200 Hz, and is reduced to 0.125 UI above 8 kHz. The green trace shows the THD+N of the DAC2
while being driven with the jitter shown on the red curve. Over the entire range of the AES jitter
tolerance test, the THD+N performance of the DAC2 is unchanged. The DAC2 easily passes the
AES jitter tolerance test without any THD+N performance degradation.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 59

Audio Precision

DAC2 - INTERFACE JITTER TOLERANCE FFT

10 kHz Test Tone at 0 dBFS, AES Jitter Tolerance Sweep

-140

+0

-120

-100

-80

-60

-40

-20

d

B

r

A

0 32k 2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 22k 24k 26k 28k 30k

Graph 15 - JITTER TOLERANCE FFT

This plot shows an series of FFTs that were acquired while running the AES jitter tolerance test.
Note that none of the 31 FFTs show any signs of jitter-induced sidebands. Note that the plots are
identical to the plots shown in Graph 3 - FFT 10 kHz. The DAC2 shows no change in performance
when the AES jitter tolerance test is applied to the digital inputs. No jitter-induced sidebands are

visible to a measurement limit that exceeds -140 dBFS.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 60

Audio Precision

11/06/12 08:15:12

DAC2 - 11K 12K IMD

DAC2 - IMD 11K 12K.at27

-160

+0

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

d

B

r

A

-160

+0

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-122.154

-128.885

d

B

r

A

0 20k 2k 4k 6k 8k 10k 12k 14k 16k 18k

1.01761k 10.0196k

Hz

dx=9.00196 kHz

dy=-6.731 dB

Graph 16 - IMD 11k 12K

This plot demonstrates that the DAC2 has very low IMD distortion. The 1 kHz difference frequency
measures -122 dB, and the 10 kHz and 13 kHz products measure about -128 dB. IMD distortion
should be well below audible levels.

Manual for DAC2 D with 2.X Firmware - Rev. H Page 61

Specifications

Audio Performance

Fs = 44.1 to 96 kHz, 20 to 20 kHz BW, 1 kHz test tone, 0 dBFS = +24 dBu (unless noted)

SNR – A-Weighted, 0 dBFS = +20 to +29 dBu

126 dB

SNR – Unweighted, 0 dBFS = +20 to +29 dBu

123 dB

THD+N, 1 kHz at 0 dBFS

-109 dBFS, -109 dB, 0.00035%

THD+N, 1 kHz at -1 dBFS

-110 dBFS, -109 dB, 0.00035%

THD+N, 1 kHz at –3 dBFS

-113 dBFS, -109 dB, 0.00035%

THD+N, 20 to 20 kHz test tone at –3 dBFS

-112 dBFS, -108 dB, 0.00040%

Frequency Response at Fs=96 kHz

+0 dB, -0.04 dB (20 to 20 kHz)

-0.04 dB at 10 Hz

-0.04 dB at 20 kHz

-0.04 dB at 40 kHz

-0.7 dB at 45 kHz

Frequency Response at Fs=48 kHz

+0 dB, -0.04 dB (20 to 20 kHz)

-0.04 dB at 10 Hz

-0.04 dB at 20 kHz

Crosstalk

-116 dB at 20 kHz

-130 dB at 1 kHz

-137 dB at 20 Hz

Maximum Amplitude of Jitter Induced Sidebands (10
kHz 0 dBFS test tone, 12.75 UI sinusoidal jitter at 1
kHz)

< -144 dB
Maximum Amplitude of Spurious Tones with 0 dBFS test
signal

< -138 dB
Maximum Amplitude of Idle Tones

< -147 dB

Maximum Amplitude of AC line related Hum & Noise

< -140 dB

Inter-channel Differential Phase (Stereo Pair – any
sample rate)

+/- 0.25 degrees at 20 kHz

Inter-channel Differential Phase (Between DAC2 Units
Fs<110 kHz) Any sample rate.

+/- 0.25 degrees at 20 kHz
Maximum Lock Time after Fs change

400 ms

Soft Mute Ramp Up/Down Time

50 ms

Mute on Receive Error

Yes

Mute on Lock Error

Yes

Mute on Idle Channel

No

50/15 us De-Emphasis Enable

Automatic in Consumer Mode

De-Emphasis Method

Digital IIR

De-Emphasis Supported at

Fs = 32, 44.1, 48 kHz

Manual for DAC2 D with 2.X Firmware - Rev. H Page 62

Group Delay (Latency)

Delay – Digital Input to Analog Output (function of
sample rate)

1.36 ms at 44.1 kHz

1.27 ms at 48 kHz

0.90 ms at 88.2 kHz

0.82 ms at 96 kHz

0.51 ms at 176.4 kHz

0.47 ms at 192 kHz

Digital Audio Inputs

Number of Digital Inputs (switch selected)

5 (1 USB, 2 Optical, 2 Coaxial)

Number of Channels

2

Input Sample Frequency Range

28 to 210 kHz (Coaxial Inputs)

28 to 96 kHz (Optical Inputs)

44.1, 48, 88.2, 96, 176.4, 192 kHz
(USB Input)

Maximum Input Word Length

24 bits

Digital Input Impedance

75 Ohms (Coaxial Inputs)

DC Blocking Capacitors on Digital Inputs

Yes (Coaxial Inputs)

Transient and Over-Voltage Protection on Digital Inputs

Yes (Coaxial Inputs)

Minimum Digital Input Level

250 mVpp (Coaxial Inputs)

Jitter Tolerance

(With no Measurable Change in Performance)

>12.75 UI sine, 100 Hz to 3 kHz

>1.5 UI sine at 20 kHz

>1.5 UI sine at 40 kHz

>1.5 UI sine at 80 kHz

>1.5 UI sine at 90 kHz

>0.25 UI sine above 160 kHz

Jitter Attenuation Method

Benchmark UltraLock2™ - all inputs

Manual for DAC2 D with 2.X Firmware - Rev. H Page 63

Balanced Analog Outputs

Number of Balanced Analog Outputs

2

Output Connector

Gold-Pin Neutrik™ male XLR

Output Impedance

60 Ohms (Attenuator off)

425 Ohms (Attenuator = 10 dB)

135 Ohms (Attenuator = 20 dB)

Analog Output Clip Point

+29 dBu

Factory Set Bypass Level (at 0 dBFS)

+24 dBu (Attenuator = 0 dB)

Output Level Range (at 0 dBFS) In ‘Variable’ Mode

Off to +24 dBu (Attenuator off)

Off to +14 dBu (Attenuator = 10 dB)

Off to +4 dBu (Attenuator = 20 dB)

Output Level Variation with Sample Rate (44.1 kHz vs.
96 kHz)

< +/- 0.006 dB

Unbalanced Analog Outputs

Number of Unbalanced Analog Outputs

4

Output Connector

RCA

Output Impedance

30 Ohms

Analog Output Clip Point

+13.5 dBu (3.7 Vrms)

Factory Set Home Theater Bypass Output Level (at 0
dBFS)

+8.2 dBu (2 Vrms)
Output Level Range (at 0 dBFS)

Off to +8.2 dBu (2 Vrms)

Output Level Variation with Sample Rate (44.1 kHz vs.
96 kHz)

< +/- 0.006 dB

HPA2TM Headphone Outputs

Number of Headphone Outputs

2

Output Connectors

¼” TRS with switch on left-hand jack

Output Impedance

< 0.11 Ohms

Output Level Control

Stereo Control on Front Panel

Output Level Range (at 0 dBFS) into 60-Ohm Load

Off to +18 dBu

Maximum Output Current

250 mA

Overload Protection (independent per channel)

Current limited at 300 mA, Thermal

Bandwidth

> 500 kHz

THD+N

-106 dB, 0.0005% into 30 Ohms at
+18 dBu (1.26W into 30 Ohms)

Manual for DAC2 D with 2.X Firmware - Rev. H Page 64

AC Power Requirements

Nominal Input Operating Voltage Range (VAC RMS)

100 – 240V

Frequency

50-60 Hz

Power

< 0.5 Watts Idle
12 Watts Typical Program
15 Watts Maximum

Fuses

5 x 20 mm (2 required)

0.5 A 250 V Slo-Blo® Type

Min/Max Operating range (VAC RMS)

90 – 260
47 – 63Hz

Dimensions

Form Factor

½ Rack Wide, 1 RU High

Depth behind front panel

8.5” (216 mm)

Overall depth including connectors but without power
cord

9.33” (237 mm)
Width

9.5” (249 mm)

Height

1.725” (44.5 mm)

Weight

DAC2 D only

3 lb.

DAC2 D with accessories and manual

4 lb.

Shipping weight

7 lb.

Status Display

Indicators - Type and Location

16 LED’s on Front Panel

Selection/Status Indication

1 – Dim/Mute
1 - Polarity
7 – Input
1 – Bypass/Calibrated Output
2 – Word length
4 – Sample Rate

Manual for DAC2 D with 2.X Firmware - Rev. H Page 65

Regulatory Compliance

RoHS Compliant Information

This statement clarifies Benchmark Media Systems, Inc. product compliance with the EU’s
(European Union) directive 2002/95/EC, or, RoHS (Restrictions of Hazardous Substances).

As of July 01, 2006, All Benchmark Media Systems, Inc. products placed on the European Union
market are compliant (containing quantity limit weight less than or equal to 0.1% (1000 ppm)
of any homogeneous Lead (Pb), Mercury (Hg), Hexavalent Chromium (Cr VI), and flame
retardant Polybrominated Biphenyls (PBB) or Polybrominated Diphenyl Ethers (PBDE)).

FCC Notice (U.S. Only)

NOTICE: This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This equipment
generates, uses, and can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a particular installation. If
this equipment does cause harmful interference to radio or television reception, which can be
determined by turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measures:

 Reorient or relocate receiving antenna.
 Increase the separation between the equipment and receiver.
 Connect the equipment into an outlet on a circuit different from that to which the receiver is

connected.

 Consult the dealer or an experienced radio/TV technician for help.

This device complies with Part 15 of the FCC rules. Operation is subject to the following two
conditions:

1. This device may not cause harmful interference.

2. This device must accept any interference received including interference that may cause
undesired operation.

Instructions to Users: This equipment complies with the requirements of FCC (Federal
Communication Commission) equipment provided that following conditions are met:

 RCA Digital Connections: Shielded 75-Ohm coaxial cable must be used.

NOTICE: Changes or modifications not expressly approved by the party responsible for
compliance could void the user's authority to operate the equipment.

FCC and RoHS Compliance Statements

Manual for DAC2 D with 2.X Firmware - Rev. H Page 66

CE Certificate of Conformity

Manual for DAC2 D with 2.X Firmware - Rev. H Page 67

Warranty Information

The Benchmark 1-Year Warranty

Benchmark Media Systems, Inc. warrants its products to be free from defects in material and
workmanship under normal use and service for a period of one year from the date of
delivery.

This warranty extends only to the original purchaser. This warranty does not apply to fuses,
lamps, batteries, or any products or parts that have been subjected to misuse, neglect,
accident, modification, or abnormal operating conditions.

In the event of failure of a product under this warranty, Benchmark Media Systems, Inc. will
repair, at no charge, the product returned to its factory. Benchmark Media Systems, Inc. may,
at its option, replace the product in lieu of repair. If the failure has been caused by misuse,
neglect, accident, or, abnormal operating conditions, repairs will be billed at the normal shop
rate. In such cases, an estimate will be submitted before work is started, if requested by the
customer.

Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export.

The foregoing warranty is in lieu of all other warranties, expressed or implied, including but not
limited to any implied warranty of merchantability, fitness or adequacy for any particular
purpose or use. Benchmark Media Systems, Inc. shall not be liable for any special, incidental,
or consequential damages, and reserves the right to change this information without notice.
This limited warranty gives the consumer-owner specific legal rights, and there may also be
other rights that vary from state to state.

Benchmark 1-Year Warranty

Manual for DAC2 D with 2.X Firmware - Rev. H Page 68

The Benchmark Extended 5-Year Warranty *

Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of
five years from the date of delivery.

*For the extended warranty to become effective, the original purchaser must register the
product at the time of purchase either by way of the enclosed registration card or through the
product registration section of the Benchmark Media Systems, Inc. website. This optional
warranty applies only to products purchased within the US and Canada and is extended only to
the original purchaser.

Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export. The terms of the extended warranty are subject to
change without notice. For products purchased outside the US and Canada, please refer to the
Extended Two 2-Year International Warranty.

The Benchmark Extended 2-Year International Warranty **

Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of
two years from the date of delivery.

**For the extended warranty to become effective, the original purchaser must register the
product at the time of purchase either by way of the enclosed registration card or through the
product registration section of the Benchmark Media Systems, Inc. website. This optional
warranty applies only to products purchased outside the US and Canada and is extended only
to the original purchaser.

Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export. The terms of the extended warranty are subject to
change without notice. For products purchased in within the US and Canada, please refer to the
Extended Five 5-Year Warranty.

Notes on Warranty Repairs

An RMA (return merchandise authorization) number, issued by our Customer Service
Department, is required when sending products for repair.

They must be shipped to Benchmark Media Systems prepaid and preferably in their original
shipping carton with the RMA number clearly visible on the exterior of the packaging. A letter
should be included giving full details of the difficulty.

Benchmark Extended Warranty Options

Manual for DAC2 D with 2.X Firmware - Rev. H Page 69

Revision H - 5/2/2019

Copyright © 2007, 2008, 2009, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019

Benchmark Media Systems, Inc.

All rights reserved.

Benchmark Media Systems, Inc.

Benchmark Media Systems, Inc.

203 East Hampton Place, STE 2

Syracuse, NY 13206

USA

PHONE: [phone]

FAX: [phone]

benchmarkmedia.com

Manual for DAC2 D with 2.X Firmware - Rev. H Page 70