Boulder 2108 User Manual

2108 Phono Preamplier

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Rev. 1.0

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Boulder Ampliers, Inc.
255 S. Taylor Ave.
Louisville, CO 80027
[phone]
www.boulderamp.com
www.facebook.com/BoulderAmpliersInc

About

About Boulder Ampliers, Inc.

Boulder was founded in 1984 and is the last high-performance audio
manufacturer operating in North America to still perform all of its own
design, engineering and manufacturing in-house. While this form of
production may be more costly than outsourcing, the resulting quality
control and reliability of the nished products are never compromised.

In 2016, Boulder moved into a new, purpose-built production facility to
increase manufacturing efciency and offer space for expansion to meet the
needs of future growth.

Thank You

Congratulations and thank you for selecting the Boulder 2108 Phono
Preamplier for your high-performance sound system. We are certain it will
provide you with many years of listening pleasure.

The 2108 represents the concerted efforts of numerous Boulder designers,
engineers, and technicians working to bring you the best audio playback
components in the world. Please take a few moments to read through this
instruction manual prior to using your 2108. This will help you understand
the many functions and capabilities of the phono preamplier. It will also
allow you to maximize the convenience and performance for which it was
engineered.

Your Boulder 2108 Phono Preamplier has undergone extensive laboratory
tests for safety, functionality and technical excellence. In addition, it has been
individually subjected to rigorous listening trials in our sound room utilizing
a wide range of musical material. No product ever leaves our factory until we
are totally satised that it achieves its full potential.

Table of Contents

Getting Started

Introduction ••••••••••••••••••••••••••••••••••••••••••••••1-1

Audio Features ••••••••••••••••••••••••••••••••••••••••••••1-1

Operational Features ••••••••••••••••••••••••••••••••••••••••1-1
Unpacking and Care ••••••••••••••••••••••••••••••••••••••••1-2
Before You Start •••••••••••••••••••••••••••••••••••••••••••1-3
How to Clean the Casework •••••••••••••••••••••••••••••••••••1-4

Installation •••••••••••••••••••••••••••••••••••••••••••••••1-5

Placement and Installation ••••••••••••••••••••••••••••••••••••1-5
Connections ••••••••••••••••••••••••••••••••••••••••••••••1-6
Making Connections to the 2108 Phono Preamplier ••••••••••••••••••1-6
Making Connections to the 2100 Power Supply ••••••••••••••••••••••1-7

Connecting the 2108 to the 2100 Power Supply •••••••••••••••••••••1-8

Connecting the Analog Outputs ••••••••••••••••••••••••••••••••1-9
Connection to AC Mains ••••••••••••••••••••••••••••••••••••1-10
Turntable Connection Types ••••••••••••••••••••••••••••••••••1-11

Connecting a Turntable •••••••••••••••••••••••••••••••••••••1-12
GROUND ••••••••••••••••••••••••••••••••••••••••••••••1-13
Connecting a Cartridge Demagnetizer •••••••••••••••••••••••••••1-14
Connecting the Outputs to a Balanced Preamplier ••••••••••••••••••1-15
Connecting the Outputs to an Unbalanced Preamplier •••••••••••••••1-16
Setup and Loading •••••••••••••••••••••••••••••••••••••••••1-17
Personality Cards •••••••••••••••••••••••••••••••••••••••••1-17
Moving Coil or Moving Magnet Selection •••••••••••••••••••••••••1-18
Cartridge Loading Adjustment - Resistive •••••••••••••••••••••••••1-19
Cartridge Loading Adjustment - Capacitive •••••••••••••••••••••••1-22
Gain Selection Adjustment •••••••••••••••••••••••••••••••••••1-23
Demagnetizer Pass-Through Selection •••••••••••••••••••••••••••1-24

Operation

Power •••••••••••••••••••••••••••••••••••••••••••••••••••2-1
Standby ••••••••••••••••••••••••••••••••••••••••••••••••••2-2
Mute ••••••••••••••••••••••••••••••••••••••••••••••••••••2-3
Input Selection •••••••••••••••••••••••••••••••••••••••••••••2-4
Demag •••••••••••••••••••••••••••••••••••••••••••••••••••2-5
Mono •••••••••••••••••••••••••••••••••••••••••••••••••••2-6
Equalization •••••••••••••••••••••••••••••••••••••••••••••••2-7
Low Cut Filter •••••••••••••••••••••••••••••••••••••••••••••2-10
Connections ••••••••••••••••••••••••••••••••••••••••••••••2-11

Table of Contents

Appendix

Technical Specications •••••••••••••••••••••••••••••••••••••••3-1

Dimensions & Weights ••••••••••••••••••••••••••••••••••••••••3-2

2108 Preamplier Section Dimensions •••••••••••••••••••••••••••••3-3
2100 Power Supply Section Dimensions •••••••••••••••••••••••••••3-4

Troubleshooting ••••••••••••••••••••••••••••••••••••••••••••3-5
Notes •••••••••••••••••••••••••••••••••••••••••••••••••••3-7

The 2108 Phono Preamplier embodies years of development and is
the evolution of the legendary 2008 Phono Preamplier, one of the
greatest phono preampliers ever made. Here are some of the fea-

Getting Started

tures that set the 2108 apart from the competition:

Audio features:

• Fully-balanced inputs and outputs.

• Surface-mount design (SMD) circuitry wherever possible.

• Three pairs of balanced inputs and two pairs of balanced outputs
on XLR connectors.

• Boulder’s own discrete 99S and 995S gain stages.

• Fully-adjustable resistive and capacitive load settings to match a
wide range of phono cartridges.

• Standard RIAA equalization as well as EMI, Columbia, and FFRR
(London/Decca) for records produced before 1955.

Getting Started

Operational features:

• Fully-machined, non-resonant chassis design.

• Switchable gain for MC (moving coil) or MM (moving magnet) car­tridges.

• Logic control to reduce operational noise.

• Mono mode to optimize monaural playback with stereo cartridges

• Four power supplies (Standby, analog left, analog right, and con­trol) in a separate power supply enclosure.

1-1

Getting Started

Unpacking and Care

The 2108 Phono Preamplier comes in two boxes and both are very
heavy. They feature nely nished casework. Please use care when
unpacking, lifting, and installing the two sections to avoid damage to
the metalwork and furniture. The 2108 Phono Preamplier weighs 37
lbs. (16.8kg) and the Power Supply weighs 48 lbs. (21.8 kg).

The Power Supply section is front-end heavy. Please be aware of this
when lifting it to avoid any accidental damage.

Be sure to save all packing materials! The 2108 is shipped in a foam
wrap to protect the ne nish of both sections. Try not to damage this
wrap in the event that the unit must be transported in the future.

Getting Started

1-2

Before You Start

The 2108 system comes in two assemblies that must be put in place

Getting Started

and connected: the 2108 Audio section and the 2100 Power Supply
section.

You should have received two large, heavy boxes. The pieces included
inside them are:

1. 2108 Audio section

2. 2100 Power Supply section

• 1 x AC power cord

• Accessory box #1 containing:

• 3 x DC cables

3. Accessory box #2 containing:

• Owner’s Manual

• PHRCA RCA-to-XLR Adaptors

• Two spare Personality Cards with labels

• Ground wire

Getting Started

If any of these pieces are missing or damaged, please contact your
dealer immediately and before continuing the installation.

1-3

Getting Started

How to Clean the Casework

If the 2108 must be cleaned, use only a soft, lint-free cloth moistened
with plain water.

Never use any type of chemical cleaner unless recommended by your

dealer or the Boulder factory.

Do not use bleach! Bleach will remove the anodized surface of the

casework.

Never use any type of abrasive to clean the casework.

If you have any questions, please contact your authorized Boulder
dealer.

Getting Started

1-4

Installation

Placement and Installation

Getting Started

Your Boulder 2108 Phono Preamplier is designed to reduce the ef­fects that external magnetic elds and radio frequencies (RF) have on
its circuitry. While placement is not critical, because of the high gain of
the 2108, known magnetic elds should be avoided whenever possi­ble. Power transformers in other pieces of nearby equipment should
be placed a minimum of 12 inches (30 cm) away.

Because it is very heavy, the 2108 must be placed on a sturdy, stable
surface.

Do not place in an enclosed rack without ventilation. Both sections
of the 2108 must have at least 2 inches (5 cm) of airspace around the
chassis for proper cooling and airow.

Getting Started

Be sure to leave access to the AC mains and DC power cables when
installing. Depending on how easy it is to access the back panels of the
2108 and 2100, it may be wise to preinstall the power and intercon­nect cables before placement.

1-5

Getting Started

Connections

Making Connections to the 2108 Phono Preamplier

Getting Started

5 1

6 7

Input Connections

1. Input 1

2. Input 2

3. Input 3

4. Ground (or Earth) Binding Posts

5. Cartridge Demagnetizer Pass-through

Output Connections.

6. Right Outputs

7. Left Outputs

2 23 3

1

98 10

8 910

5

4

Power Supply Connections.

8. Power R Audio

9. Power L Audio

10. Power Digital (Control)

1-6

Getting Started

Making Connections to the 2100 Power Supply

Getting Started

2

1

1. AC Mains Connection

2. Master AC Power Switch

3. Right Audio DC Power

4. Left Audio DC Power

5. Digital (Control) DC Power

3 45

1-7

Getting Started

Connecting the 2108 to the 2100 Power Supply

Connect the DC cables from the 2100 power supply to the 2108 Pho­no Preamplier. Because the cable connectors are keyed, they cannot
be installed incorrectly.

Please note that the Digital (Control) DC cable has a different number
of pins and cannot be connected to the Audio power connectors.

WARNING: Do not turn on the 2100 until all DC power connections have
been made!

It is important never to disconnect any of the DC power cables when the
unit is powered ON via the AC master power switch or damage may occur,
even when the 2108 is in Standby mode!

Always turn the unit OFF from the rear panel of the 2100 power supply
before disconnecting any of the DC power cables.

Getting Started

1-8

Connecting the Analog Outputs

Connect the left and right interconnect cables from one of the 2108’s

Getting Started

LEFT OUTPUTS and RIGHT OUTPUTS to your preamplier or inte-
grated amplier’s left and right input connections. To maintain best
sound quality, Boulder recommends that balanced audio connections
always be used. Because the 2108’s output connections are in paral­lel, it does not matter which connection you use, as there is no sonic
difference.

The 2108 has balanced audio connections via XLR jacks. If you are
connecting the 2108 to a preamplier or amplier that does not have
balanced input connections, you will either need a pair of Boulder
XLR-to-RCA adaptors (ABL2) or need to have your cables properly
terminated. A diagram for the proper cable conguration is shown
below.

Getting Started

1-9

2108

Getting Started

Connection to AC Mains

Connect the AC power cord to the 2100’s AC Mains Connection and
plug it into your AC mains wall outlet.

WARNING: It is important never to disconnect any of the DC power cables
when the unit is powered ON via the AC master power switch or damage
may occur, even when the 2108 is in Standby mode!

Always turn the unit OFF from the rear panel of the 2100 power supply or
disconnect the AC mains power cord before disconnecting any of the DC
power cables.

Getting Started

1-10

Turntable Connection Types

To get started listening, you only need to connect a turntable to the

Getting Started

2108 as you would any other phono preamplier. Please take note of
the following:

The 2108 can be connected to many different types of turntables. To
fully realize the sonic potential of your 2108 Phono Preamplier, use
balanced cable connections with XLR terminations whenever possible.
Balanced XLR cables minimize interference from magnetic, hum, and
RF sources.

Getting Started

1-11

Getting Started

Connecting a Turntable

Because a phono cartridge is actually a balanced source, balanced
inputs are provided on the 2108. Connect the output cables from your
turntable to the LEFT and RIGHT CHANNEL INPUT 1 connections of
the 2108.

For turntables or systems that have more than one tonearm connec­tion, connect the additional phono sources to the left and right con­nections for INPUT 2 and INPUT 3.

Please note the following instructions to avoid picking up hum in the
system:

Do not short pin 1 (chassis/ground) to either pin 2 or 3 of the XLR con­nector at any point in the cable, turntable chassis, or tonearm. This will
cause hum in the system. Pins 2 and 3 must only be connected directly
to the cartridge pins. Proper wiring diagrams are shown on the next
page.

Getting Started

Use only a connection from Pin 1 of the turntable’s XLR connector to
the turntable chassis or the provided ground wire from the 2108’s
rear panel Ground Binding Post to the turntable chassis. Using both
may form a ground loop, which will cause hum.

If your turntable does not have XLR connections, one pair of Boulder
PHRCA Phono Adaptors is provided. These will convert the 2108’s
inputs to RCA and give acceptable performance. A separate ground
wire is also provided.

CAUTION: If your turntable does not have XLR connectors, do not use the

Boulder ABL2 input adaptor or any other “standard” RCA to XLR adaptors.
These are not intended for phono use, as they short pin 1 to pin 3 and will
cause hum in your system. Only use the Boulder PHRCA Phono Adaptors.

UNBALANCED RCA CABLE, PIN 2+ INPUT, PIN 3- INPUT, PIN 1

1-12

GROUND

Getting Started

Getting Started

1-13

Getting Started

Connections

Connecting a Cartridge Demagnetizer

The 2108 is able to connect an external cartridge demagnetizer to
your phono cartridge via a pair of RCA connectors on the rear panel.

Connect each channel of the demagnetizer to the RCA inputs labeled
DEMAG on the rear panel of the 2108.

WARNING: Do not demagnetize a moving magnet (MM) cartridge or dam­age to the cartridge will occur!

For Further information about the demagnetizer circuit, please see
pages 1-24 and 2-5.

Getting Started

1-14

Connecting the Outputs to a Balanced Preamplier

The 2108 has balanced output connections on XLR jacks. With the

Getting Started

low output impedance of the 2108 Phono Preamplier, distances of
more than 100 meters between the 2108 and preamplier or integrat­ed amplier are practical.

Connect the LEFT and RIGHT OUTPUT interconnects from the 2108
to your preamplier or integrated amplier’s left and right inputs. To
maintain the best sound quality, Boulder recommends that balanced
interconnections always be used. Because the 2108’s dual output con­nections are in parallel, it does not matter which connection you use,
as there is no sonic difference between the two.

Getting Started

1-15

Getting Started

Connecting the Outputs to an Unbalanced Preamplier

If you are connecting the 2108 to a preamplier or amplier that does
not have balanced input connections, you will either need a pair of
Boulder XLR-to-RCA adaptors (ABL2) or need to have your cables
properly terminated. A diagram for the proper cable conguration is
shown below.

This cable connects pin 1 of the XLR to the shield of the cable and pin
2 to the center pin of the RCA. It leaves the negative output (pin 3)
unconnected.

Connecting the unused output pin (usually pin 3) to ground will cause
excessive ground currents and degrade performance. Use an ohm
meter or continuity checker to determine how your cable is wired.

NOTE: The 2108 Phono Preamplier conforms to the standard of pin 2 as

high or “hot” for all balanced analog inputs and outputs.

Getting Started

2108

1-16

Setup and Loading

Personality Cards

Getting Started

Each input connector of the 2108 has a slot below it for a Personality
Card, one for the left and right channels of each input. These cards
have four functions:

1. Selection of the type of cartridge to be used with the input (MC or

MM)

2. Adjustment of the loading for the cartridge to be used with the

input (resistive or capacitive)

3. Determining the gain level of the input

4. Enabling the Demagnetizer pass-through function (if selected)

On each Personality Card there is a DIP switch selector for choosing
the cartridge type, gain level, and enabling demagnetizing.

Getting Started

WARNING: Always press the Standby button on the front panel to place
the 2108 in Standby mode before removing or installing any Personality
Card! Failure to place the unit in Standby may result in very loud pops
through the system!

To remove a Personality Card, pull the tab on the card until it slides out
of the rear panel. You may have to pull hard to remove the card. To in­stall a Personality Card, push it into the rear panel until it is completely
seated and the face of the card is ush with the rear panel.

1-17

Getting Started

Moving Coil or Moving Magnet Selection

Set the Cartridge Type DIP Switch to either MC (Moving Coil) or MM
(Moving Magnet), depending on the type of cartridge mounted to your
turntable.

From the factory, the Personality Cards for INPUT 1 and INPUT 2 are
set to the MC position. When the Cartridge Type DIP Switch is set to
the MC position, an additional low-noise 20 dB gain stage is inserted
at the input for a total of 60 or 70 dB of gain, depending on the setting
of the Gain Selection switch.

The Personality Card for INPUT 3 is set to the MM position. This is
the most common setting for moving magnet cartridges. Total gain in
the MM position is 40 or 50 dB, depending on the setting of the Gain
Selection switch.

Getting Started

1-18

Cartridge Loading Adjustment - Resistive

Set the Cartridge Type DIP Switch to either MC (Moving Coil) or MM

Getting Started

(Moving Magnet), depending on the type of cartridge mounted to your
turntable.

From the factory, the Personality Cards for INPUT 1 and INPUT 2 are
set to the MC position and the resistive cartridge loading is 100Ω, with
a maximum unadjusted load of 1000Ω (no resistor installed). When
the Cartridge Type DIP Switch is set to the MC position, an additional
low-noise 20 dB gain stage is inserted at the input for a total of 60 or
70 dB of gain, depending on the setting of the Gain Selection switch.

The Personality Card for INPUT 3 is set to MM and no additional
loading resistor is installed, so the resistive cartridge loading is 47kΩ.
This is the most common setting for moving magnet cartridges. Total
gain in the MM position is 40 or 50 dB, depending on the setting of the
Gain Selection switch.

Getting Started

For MC cartridges the maximum resistive loading is 1000Ω. This is the
value when there is no resistor installed in position R1 of the Person­ality Card. This value can be lowered by installing a resistor in position
R1. The value for the load when a resistor is installed is calculated by
the following: R1 = 1/(1/RDESIRED - .001) or by using the following
table.

Desired Cartridge Loading Value Resistor Value To Install in Position R1

50 ohms 53 ohms

75 ohms 81 ohms
100 ohms 111 ohms
125 ohms 143 ohms
150 ohms 176 ohms

1-19

Getting Started

Desired Cartridge Loading Value Resistor Value To Install in Position R1

175 ohms 212 ohms
200 ohms 250 ohms
225 ohms 290 ohms
250 ohms 333 ohms
275 ohms 379 ohms
300 ohms 429 ohms
325 ohms 481 ohms
350 ohms 538 ohms
375 ohms 600 ohms
400 ohms 667 ohms
425 ohms 739 ohms
450 ohms 818 ohms
475 ohms 905 ohms
500 ohms 1000 ohms
525 ohms 1105 ohms
550 ohms 1222 ohms
575 ohms 1353 ohms
600 ohms 1500 ohms
625 ohms 1667 ohms
650 ohms 1857 ohms
675 ohms 2077 ohms
700 ohms 2333 ohms
725 ohms 2636 ohms
750 ohms 3000 ohms
775 ohms 3444 ohms
800 ohms 4000 ohms
825 ohms 4714 ohms

Getting Started

1-20

Desired Cartridge Loading Value Resistor Value To Install in Position R1

Getting Started

For MM cartridges, the maximum resistive load is 47kΩ. This is the
value when there is no resistor installed in position R1 of the Person­ality Card. This value can be lowered by installing a resistor in position
R1. The value for the load when a resistor is installed is calculated
by the following: R1 = 1/(1/R
below:

Getting Started

850 ohms 5667 ohms
875 ohms 7000 ohms
900 ohms 9000 ohms
925 ohms 12333 ohms
950 ohms 19000 ohms
975 ohms 39000 ohms

1000 ohms Open (no resistor installed)

- .0000213) or by using the table

DESIRED

Desired Cartridge Loading Value Resistor Value To Install in Position R1

1000 ohms 1020 ohms

5000 ohms 5620 ohms
10000 ohms 12700 ohms
20000 ohms 34800 ohms
47000 ohms Open (no resistor installed)

1-21

Getting Started

Cartridge Loading Adjustment - Capacitive

The 2108’s inputs have “parasitic” capacitive of less than 50 pF direct­ly across the cartridge inputs. If desired, additional capacitance can be
added on the Personality Card at position C1. The selected capacitor
value should be 50 pF less than the desired value.

Solder holes are provided for two different sizes of capacitors. There
are two pairs of solder holes provided, as shown. Each left or right pair
is connected together so that it does not matter which pair you use.
The capacitor must only be soldered to one of the left and one of the
right holes.

All solder joints on the Personality Card have grommets installed to
reinforce the solder joint when parts are added or removed. Do not
remove these grommets.

NOTE: While some cartridge manufacturers may recommend additional ca-

pacitive loading, we suggest that you do not do so. Additional capacitance
lowers the resonant frequency of the capacitor and the cartridge winding
inductance, particularly with MM cartridges while the resonance peak
remains just as high and will increase distortion.

Getting Started

Instead, we suggest trying a lower resistor value. The lower the value, the
“heavier” the load and the lower the resonance peak (not frequency), which
will give better damping to the cartridge.

With low-level MC cartridges there is practically no effect with capacitive
loading, as the cartridge output impedance is inherently very low.

1-22

Gain Selection Adjustment

The middle switch on the Cartridge Type DIP Switch can be set to

Getting Started

either LO GAIN or HI GAIN (+10 dB). This switch is used to raise the
overall gain of the input for lower output cartridges. When using
cartridges with very low output (less than 0.2 mV), it is recommended
that the HI GAIN setting is used.

If you do not know which setting to use, try the HI GAIN setting rst.
If you have to signicantly reduce the volume of your preamplier in
comparison to other inputs, then the LO GAIN setting should be used
to ensure that you do not overload the input of your preamplier.

Getting Started

1-23

Getting Started

Demagnetizer Pass-Through Selection

A pair of RCA connectors on the rear panel of the 2108 are provided
for connection to an external cartridge demagnetizer. If you wish to
demagnetize a cartridge connected to a particular input of the 2108,
set the Cartridge Type DIP Switch to DEMAG OK. If you will not
connect a cartridge demagnetizer to the input, set the switch to NO
DEMAG.

Getting Started

1-24

Operation

Operation

Power

With all of the connections and adjustments made, you are now ready
to listen to your Boulder 2108 Phono Preamplier.

To turn the 2108 ON, move the Master AC Power Switch located on
the rear panel of the 2100 Power Supply upwards. The 2108 will then
go into Standby mode.

To bring the 2108 out of Standby mode, press the STANDBY button
on the front panel. The LED above the STANDBY button will illumi­nate white and the 2108 will be powered on.

To turn the 2108 OFF, move the Master AC Power Switch located on
the rear panel of the 2100 Power Supply downwards. The LED on the
front panel of the power supply will not be illuminated when the 2108
is turned OFF.

2-1

Operation

Standby

To bring the 2108 out of Standby mode, press the standby button on
the front panel. The LED on the front panel of the 2100 Power Sup­ply will turn white and the 2108 will automatically unmute when it is
ready for listening.

To place the 2108 in Standby mode, press the Standby button on the
front panel. The LED on the front panel of the 2100 Power Supply will
no longer be illuminated and the 2108 will go into power saving mode.

Operation

2-2

Operation

Mute

The Boulder 2108 Phono Preamplier provides an output muting
feature that is turned on by four different conditions. When the 2108
is in Mute mode, the small LED above the MUTE button will illuminate

amber.

First, the outputs are muted for three seconds when the 2108 is pow­ered ON. Pressing the MUTE button while the 2108 is in this state will
have no effect.

Second, the outputs can be temporarily muted at any time for your
convenience. To temporarily mute the outputs, press the front panel
MUTE button. Pressing the MUTE button a second time will unmute
the 2108’s outputs.

Operation

Third, the outputs of the 2108 will automatically be muted for three
seconds when an INPUT or EQUALIZATION button is pressed. After
three seconds, the outputs will automatically unmute and operation
will return to normal.

Fourth, when the 2108 is turned OFF, the outputs will be muted.

2-3

Operation

Input Selection

The Boulder 2108 Phono Preamplier provides three pairs of inputs
for use with three different phono cartridges from one or more turnta­bles.

To select an input, press one of the INPUT buttons on the front panel
of the 2108. The LED above the selected input will turn white. When
changing inputs, the 2108 will mute the outputs for three seconds.

NOTE: Do not select an input that does not have a cartridge connected. If

it is necessary to disconnect all of the inputs, the MUTE button should be
pressed or the 2108 should be placed in Standby mode.

Operation

2-4

Operation

Operation

Demag

Some moving coil cartridge manufacturers have an external accessory
used to demagnetize their particular phono cartridge. The 2108 in­cludes a convenient circuit that allows this accessory to be used with­out having to disconnect any of the input connections.

WARNING: Do not demagnetize a moving magnet (MM) cartridge or dam­age to the cartridge will occur! Boulder assumes no liability for cartridges
damaged by the improper use of the Demagnetizer function.

To enable use of the Demagnetizer pass-through, an external cartridge
demagnetizer appropriate for your particular cartridge must be con­nected to the Demagnetizer inputs on the rear panel of the 2108 and
the DEMAG switch on the input’s Personality Card must be set to
DEMAG OK.

Select the input for the cartridge to be demagnetized by pressing the
button for that input, then press the DEMAG button on the front pan­el of the 2108. This will mute the outputs of the 2108. The LED above
the DEMAG button will illuminate red and the LED above the MUTE
button on the front panel will be illuminated amber. You can then turn
on and operate the cartridge demagnetizer as per the demagnetizer
manufacturer’s instructions. When the demagnetizer’s operation is
complete, press the DEMAG button again. The DEMAG LED will no
longer be illuminated and the inputs will once again be connected to
the cartridge. After three seconds the MUTE LED will turn off and
operation will return to normal.

When in use, only the inputs with Personality Cards set to DEMAG OK
will be connected to the cartridge demagnetizer through the 2108.

WARNING: Always turn the system volume all the way down or mute the

preamplier when using the Demagnetizer function of the 2108!

2-5

Operation

Mono

When played with a stereo cartridge, monaural or “mono” recordings
can be enhanced by mixing the left and right channels to create a true
monaural audio signal. It is possible to do this with the 2108 by putting
the unit in MONO mode.

When the MONO button on the front panel of the 2108 is pressed,
the LED above the MONO button will illuminate amber to indicate
that the Mono circuit is active.

To return the 2108 to stereo operation, press the MONO button on
the front panel and the LED will no longer be illuminated.

Operation

2-6

Operation

Equalization

The Boulder 2108 Phono Preamplier provides the standard RIAA
equalization curve for recordings produced after 1955, along with the
EMI, Columbia, and FFRR curves for records manufactured before

1955.

Select the equalization curve you wish to use by pressing the button
labeled with the name of that particular curve. For example, pressing
the “RIAA” button will activate RIAA equalization.

The three remaining curves may be selected by pressing the button
labeled with their respective names. When active, the LED above the
RIAA button will be illuminated amber. All other EQ options will illu­minate white.

Operation

When changing equalization settings, the 2108 will immediately mute
the outputs and the MUTE light will illuminate amber for 3 seconds.
After that time, the output will be unmuted and the MUTE indicator
will turn off.

2-7

Operation

Operation

2-8

Operation

Operation

2-9

Operation

Low Cut Filter

The Boulder 2108 Phono Preamplier uses a 3-pole (18 dB/octave)
low cut lter that may be switched to one of two frequencies or can be
turned off. When the Low Cut circuit is activated, response will be -3
dB at 10 Hz or 20 Hz.

Because this lter is fairly steep, its effect is virtually negligible in the
audio band. It is recommended that it be kept turned on in order to
avoid excessive woofer travel caused by warped or damaged records.

Select the low cut lter point by pressing the 10 Hz or 20 Hz button.
The indicator above the button will illuminate white.

To completely turn off the lter, press the button labeled OUT. The
low cut lter will be deactivated and the LED indicator will turn off.

WARNING: Due to the low frequency content of some recordings, care

should be taken with the volume level when turning the low cut lter ON or

OFF as there may be an audible transient or click through the loudspeakers.
This effect is normal.

Operation

2-10

Operation

Operation

Recording

Connections

The 2108 Phono Preamplier has two pairs of outputs. These outputs
are connected in parallel, so there is no benet to using one pair of
outputs over the other.

When one pair of outputs is connected to a preamplier, the second
pair of outputs can be connected to a recording device. It is possible to
use balanced or unbalanced connections for both inputs and outputs
as described in Section 1, “Connections.”

2-11

Appendix

Technical Specications

Inputs 3 x 3-pin balanced XLR,

adaptable to unbalanced

Outputs 2 x 3-pin balanced XLR,

adaptable to unbalanced

Input Impedance MC: maximum 1000Ω,

MM: 47kΩ. Resistive
and capacitive loading
adjustable on individual
Personality Cards.

Output Impedance 100Ω Balanced

Maximum Output Level 28 Vrms

Distortion, THD 0.005%

1 kHz Gain, RIAA MC: 70 or 60 dB, MM: 50

Noise (EIN), MC 160 uV A-wtd, 275 uV

Frequency Response, 20 Hz to 20kHz RIAA: ±0.10 dB

Crosstalk, L to R or R to L -100 dB or better, 20 Hz

Power Requirements 90-120V / 200-240V,

Appendix

Power Consumption 75W Max

All specications measured at 240 VAC mains Power

3-1

or 40 dB

Flat, 20 Hz to 20 kHz

to 20 kHz

50—60 Hz

Appendix

Dimensions and Weights

2108 Phono Preamplier Chassis: 18” W x 15.5” D x 5” H

45.7 cm W x 39.4 cm D x 12.7 cm H
(37 lbs./16.8 kg)

2100 Power Supply Chassis: 18” W x 15.5” D x 4.25” H

45.7 cm W x 39.4 cm D x 10.8 cm H
48 lbs. (21.8 kg)

2108 Phono Preamplier Shipping: 18” W x 16” D x 5” H

47.5 cm W x 41 cm D x 12.7 cm H
(51 lbs./23.2 kg)

2100 Power Supply Shipping: 24” W x 21” D x 12” H

61 cm H x 54 cm D x 31 cm H

69.5 lbs. (31.6 kg)

3-2

Appendix

2108 Preamplier Section Dimensions (Inches)

15.225

BOULDER 2108

PHONO PREAMPLIFIER

DIMENSIONS

18.000

2.000

14.000

2.000

15.225

5.040

.967

.725

BOULDER 2108

PHONO PREAMPLIFIER

DIMENSIONS

5.040

BOULDER 2108

PHONO PREAMPLIFIER

DIMENSIONS

15.971

Appendix

Appendix

3-3

.967

.725

2.000 10.500

Appendix

15.225

15.745

4.040

.965

2100 Power Supply Section Dimensions (Inches)

15.745

4.040

.965

15.225

18.000

14.000

Appendix

3-4

SYMPTOM CAUSE REMEDY

Appendix

No power indica­tion on 2100

Red LED indica­tor on 2100

White power
indication, but no
sound

Power Switch is not in
ON position

2108 is not plugged in

Home circuit breaker is
tripped

Low line voltage Have line voltage checked

Defective power cable

Defective 2108 Return 2108 to dealer for service

Phono preamplier is
booting up

Defective power supply

Defective 2108 phono
preamplier

No signal from one
channel of turntable

No signal out to pream­plier

2108 is Muted, MUTE
LED ON

Move Power Switch to ON posi­tion

Connect power cord to AC mains
outlet

Reset home circuit breaker

Have power cable tested or re­placed

Wait until boot process completes

Return 2100 and 2108 to dealer
for service

Return 2100 and 2108 to dealer
for service

Check turntable cables and con­nections

Check cables and connections to
preamplier

Push MUTE button to turn Mute
function OFF

Hum through
loudspeakers

Appendix

3-5

No ground connection Check or install ground wire

Duplicate ground con­nection

2108 or turntable is too
close to another compo­nent or power supply

Partial or bad connec­tion at phono cartridge

Use only one ground wire to
turntable or use the ground in a
balanced cable

Move 2108 and/or turntable away
from power supply

Check and/or correct connections
at phono cartridge

Appendix

One channel
louder than the
other

GAIN switches not set
equally

MC/MM switches no
set equally

Cartridge loading is not
set equally

Set GAIN switches on Personality
Cards to same setting

Set MC/MM switches on Person­ality Cards to same setting

Check cartridge loads on Person­ality Cards

3-6

Appendix

Notes:

Appendix

Appendix

3-7

Appendix

Notes:

3-8

Appendix