dbx Pro 386 User Manual

®

386

Dual Vacuum

Tube Preamp

w/Digital Out

User Manual

WARNING FOR YOUR PROTECTION

PLEASE READ THE FOLLOWING:

KEEP THESE INSTRUCTIONS

HEED ALL WARNINGS

FOLLOW ALL INSTRUCTIONS

CLEAN ONLY WITH A DAMP CLOTH.

DO NOT BLOCK ANY OF THE VENTILATION OPENINGS. INSTALL IN
ACCORDANCE WITH THE MANUFACTURERS INSTRUCTIONS.

DO NOT INST ALL NEAR ANY HEAT SOURCES SUCH AS RADIATORS,
HEAT REGISTERS, STOVES; OR OTHER APPARATUS (INCLUDING
AMPLIFIERS) THAT PRODUCE HEAT.

ONLY USE ATT ACHMENTS/ACCESSORIES SPECIFIED BY THE MAN­UFACTURER.

UNPLUG THIS APPARATUS DURING LIGHTNING STORMS OR WHEN
UNUSED FOR LONG PERIODS OF TIME.

WATER AND MOISTURE: Appliance should not be used near water

(e.g. near a bathtub, washbowl, kitchen sink, laundr y tub, in a wet
basement, or near a swimming pool, etc). Care should be taken so
that objects do not fall and liquids are not spilled into the enclosure
through openings.

POWER SOURCES: The appliance should be connected to a power
supply only of the type described in the operating instructions or as
marked on the appliance.

GROUNDING OR POLARIZATION: Precautions should be taken so
that the grounding or polarization means of an appliance is not
defeated.

POWER CORD PROTECTION: Power supply cords should be routed
so that they are not likely to be walked on or pinched by items placed
upon or against them, paying particular a ttention to cords at plugs,
convenience receptacles, and the point where they exit from the
appliance.

SERVICING: To reduce the risk of fire or electric shock, the user
should not attempt to service the appliance beyond that described in
the operating instructions. All other servicing should be referred to
qualified service personnel.

FOR UNITS EQUIPPED WITH EXTERNALLY ACCESSIBLE FUSE
RECEPTACLE: Replace fuse with same type and rating only.

MULTIPLE-INPUT VOLTAGE: This equipment may require the use of

a different line cord, attachment plug, or both, depending on the
available power source at installation. Connect this equipment only to
the power source indicated on the equipment rear panel. To reduce
the risk of fire or electric shock, refer ser vicing to qualified service
personnel or equivalent.

SAFETY INSTRUCTIONS

NOTICE FOR CUSTOMERS IF YOUR UNIT IS EQUIPPED WITH A POWER CORD.

WARNING: THIS APPLIANCEMUST BE EARTHED.

The cores in the mains lead are coloured in accordance with the following code:

GREEN and YELLOW - Earth BLUE - Neutral BROWN - Live

As colours of the cores in the mains lead of this appliance may not correspond with
the coloured markings identifying the terminals in your plug, proceed as follows:

• The core which is coloured green and yellow must be connected to the ter­minal in the plug marked with the letter E, or with the earth symbol, or
coloured green, or green and yellow.

• The core which is coloured blue must be connected to the terminal marked
N or coloured black.

• The core which is coloured brown must be connected to the terminal
marked L or coloured red.

This equipment may require the use of a different line cord, attachment plug, or
both, depending on the available power source at installation. If the attachment
plug needs to be changed, refer servicing to qualified service personnel who
should refer to the table below. The green/yellow wire shall be connected direct­ly to the units chassis.

WARNING: If the ground is defeated, certain fault conditions in the unit or in the
system to which it is connected can result in full line voltage between chassis and
earth ground. Severe injury or dea th can then result if the chassis and earth
ground are touched simultaneously.

The symbols shown above are internationally accepted symbols that warn of
potential hazards with electrical products. The lightning flash with arrowpoint
in an equilateral triangle means that there are dangerous voltages present
within the unit. The exclamation point in an equilateral triangle indicates that
it is necessary for the user to refer to the owner’s manual.

These symbols warn that there are no user serviceable parts inside the unit.
Do not open the unit. Do not attempt to service the unit yourself. Refer all
servicing to qualified personnel. Opening the chassis for any reason will void
the manufacturer’s warranty. Do not get the unit wet. If liquid is spilled on
the unit,shut it off immediately and take it to a dealer for service. Disconnect
the unit during storms to prevent damage.

IMPORTANT SAFETY INSTRUCTIONS

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC

SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE

CONDUCTOR

L
N
E

LIVE

NEUTRAL

EARTH GND

WIRE COLOR

Normal Alt

BROWN

BLUE

GREEN/YEL

BLACK
WHITE

GREEN

U.K. MAINS PLUG WARNING

A molded mains plug that has been cut off from the cord is unsafe.

Discard the mains plug at a suitable disposal facility. NEVER UNDER

ANY CIRCUMSTANCES SHOULD YOU INSERT A DAMAGED OR CUT
MAINS PLUG INTO A 13 AMP POWER SOCKET . Do not use the mains

plug without the fuse cover in place. Replacement fuse covers can be
obtained from your local retailer. Replacement fuses are 13 amps and
MUST be ASTA approved to BS1362.

LITHIUM BATTERY

WARNING

CAUTION!

This product may contain a lithium battery.There is danger of
explosion if the battery is incorrectly replaced.Replace only
with an Eveready CR 2032 or equivalent.Make sure the bat­tery is installed with the correct polarity. Discard used batter­ies according to manufacturer’s instructions.

ADVARSEL!

Lithiumbatteri - Eksplosjonsfare.Ved utskifting benyttes kun
batteri som anbefalt av apparatfabrikanten. Brukt batteri
returneres apparatleverandøren.

ADVARSEL!

Lithiumbatteri - Eksplosionsfare ved fejlagtig håndtering.
Udskiftning må kun ske med batteri av samme fabrikat og
type. Levér det brugte batteri tilbage til leverandøren.

VAROITUS!

Paristo voi räjähtää,jos se on virheellisesti asennettu.Vaihda
paristo ainoastaan laitevalmistajan suosittelemaan tyyppin.
Hävitä käytetty paristo valmistajan ohjeiden mukaisesti.

VARNING!

Explosionsfara vid felaktigt batteribyte.Använd samma batteri­typ eller en ekvivalent typ som rekommenderas av apparattil­lverkaren.Kassera använt batteri enligt fabrikantens instruk­tion.

IMPORTANT SAFETY INSTRUCTIONS

ELECTROMAGNETIC

COMPATIBILITY

This unit conforms to the Product Specifications
noted on the Declaration of Conformity.
Operation is subject to the following two condi­tions:

• this device may not cause harmful inter­ference, and

• this device must accept any interference
received, including interference that
may cause undesired operation.

Operation of this unit within significant electro­magnetic fields should be avoided.

DECLARATION OF

CONFORMITY

Manufacturer’s Name: dbx Professional Products
Manufacturer’s Address: 8760 S. Sandy Parkway

Sandy, Utah 84070, USA

declares that the product:

Product name: dbx 386
Product option: N/A

conforms to the following Product Specifications:

EMC: EN 55013 (1990)

EN 55020 (1991)

Supplementary Information:

The product herewith complies with the require­ments of the Low Voltage Directive 73/23/EEC
and the EMC Directive 89/336/EEC as amended
by Directive 93/68/EEC.

dbx Professional Products
Vice-President of Engineering
8760 S. Sandy Parkway
Sandy, Utah 84070, USA
December 15, 1999

European Contact: Your Local dbx Sales and Service
Office or

Harman Music Group
8760 South Sandy Parkway
Sandy, Utah
84070 USA
[phone]
[phone]

Table of Contents

386

Introduction

0.1 Defining the 386................................................i

0.2 Service Contact Info .........................................ii

0.3 Warranty............................................................ii

0.4 Installation Recommendations........................iii

Section 1 - Getting Star ted

1.1 Rear Panel Connections...................................2

1.2 Front Panel Connections..................................3

1.3 Type IV™ Conversion System Controls..........4

Section 2 - Analog Applications

2.1 Basic Connection..............................................6

2.2 Connection to a Mixing Console.....................6

2.3 Direct Connection to a Recorder ....................7

Section 3 - Digital Applications

3.1 Digital Output Front Panel Functions ...........10

3.2 Digital Rear Panel Connections .....................10

3.3 Sync Input Sample Rate Selection.................11

3.4 Direct Connection to a DAW (CPU) .............12

3.5 Direct Connection to a Digital Mixer ............13

3.6 A/D Conversion..............................................14

3.7 Multi-Tracking to Digital................................15

3.8 Analog and Digital Output Applications ......16

Appendix

Sync Input Info .....................................................18

Block Diagram......................................................19

dbx Type IV™ Conversion System......................20

D.1 Noise-Shaping Algorithms.............................25

D.2 Truncation......................................................25

D.3 Specifications.................................................26

386 User Manual

Table of Contents

®

INTRO

CUSTOMER SERVICE INFO

386 DEFINED

WARRANTY INFO

®

INTRODUCTION

386

Introduction

386 User Manual

i

386

Congratulations on your purchase of the dbx 386 Dual Vacuum Tube Preamp with digital out­put capabilities. For over 25 years, dbx has been the industry leader in dynamics processing.
With the introduction of the 386, we offer the classic smooth and warmth qualities of tube
microphone pre-amplification, combined with the state-of-the-art proprietary dbx Type IV™
conversion system to offer the best characteristics of both analog and digital recording capabil­ities.

This manual will be your guide to understanding the full functionality of the powerful 386. After
you have become familiar with the unit, we encourage you to experiment and find creative
ways that the 386 can help you optimize your specific application.

The dbx 386 Dual Vacuum Tube Preamp provides the user with Dual Vacuum tube microphone
preamp capabilities in the analog domain as well as giving you pristine digital output capabil­ities. Listed below, are some of features available to you in the 386:

• Two channel tube microphone pre-amplifier

• 200V Tube Plate Voltage

• Insert Jack

• 60 dB of microphone gain and +/- 15 dB of output gain

• Selectable mic/line switch

• 48 volt phantom power

• 20 dB pad

• 75 Hz low cut filter

• Phase reverse

• 12 segment LED analog/digital level meter

• Type IV™ conversion system

• Selectable 96 kHz, 88.2 kHz, 48 kHz, or 44.1 kHz sampling rate

• 24, 20, and 16 bit wordlengths

• Selectable dither and noise shaping

• AES/EBU and S/PDIF digital outputs

• Word clock sync input and output

• Separate analog and digital output control

With the dbx proprietary patent-pending TSE™ Tape Saturation Emulation and TYPE IV™
Conversion System, your signal retains its analog warmth and character, with the pristine clari­ty demanded by today’s digital standards. In addition, the 386 offers 96kHz A/D conversion,
which results in improved frequency response.

0.1 Defining the 386

INTRODUCTION

®

Introduction

386

386 User Manual

If you require technical support, contact dbx Customer Service. Be prepared to accurately
describe the problem. Know the serial number of your unit - this is printed on a sticker attached
to the rear panel. If you have not already taken the time to fill out your warranty registration
card and send it in, please do so now.

Before you return a product to the factory for service, we recommend you refer to the manu­al. Make sure you have correctly followed installation steps and operation procedures. If you
are still unable to solve a problem, contact our Customer Service Department at [phone]
for consultation. If you need to return a p roduct to the factory for service, you MUST contact
Customer Service to obtain a Return Authorization Number.

No returned products will be accepted at the factory without a Return Authorization Number.
Please refer to the warranty below, which extends to the first end-user. After expiration of the

warranty, a reasonable charge will be made for parts, labor, and packing if you choose to use
the factory service facility. In all cases, you are responsible for transportation charges to the fac­tory. dbx will pay return shipping if the unit is still under warranty.

Use the original packing material if it is available. Mark the package with the name of the ship­per and with these words in red: DELICATE INSTRUMENT, FRAGILE! Insure the package prop­erly. Ship prepaid, not collect. Do not ship parcel post.

This warranty is valid only for the original purchaser and only in the United States.

1). The warranty registration card that accompanies this product must be mailed within 30 days

after purchase date to validate this warranty. Proof-of-purchase is considered to be the bur­den of the consumer.

2). dbx warrants this product, when bought and used solely within the U.S., to be free from

defects in materials and workmanship under normal use and service.

3). dbx liability under this warranty is limited to repairing or, at our discretion, replacing defec-

tive materials that show evidence of defect, provided the product is returned to dbx WITH
RETURN AUTHORIZATION from the factory, where all parts and labor will be covered up
to a period of two years. A Return Authorization number must be obtained from dbx by
telephone. The company shall not be liable for any consequential damage as a result of the
product's use in any circuit or assembly.

4). dbx reserves the right to make changes in design or make additions to or improvements

upon this product without incurring any obligation to install the same additions or
improvements on products previously manufactured.

5). The foregoing is in lieu of all other warranties, expressed or implied, and dbx neither

assumes nor authorizes any person to assume on its behalf any obligation or liability in con­nection with the sale of this product. In no event shall dbx or its dealers be liable for spe­cial or consequential damages or from any delay in the performance of this warranty due
to causes beyond their control.

0.3 W arranty

0.2 Service Contact Info

ii

®

Introduction

386 User Manual

iii

386

Install the 386 in your rack with the provided rack screws. It is essential that when the 386 is
being mounted in a rack mounting enclosure, the unit should be positioned with enough room
(at least one centimeter at the top and one centimeter at the bottom of the unit) to allow prop­er ventilation. The 386 should not be mounted above or below anything that generates exces­sive heat. Ambient temperatures should not exceed 1130F (450C) when equipment is in use.
Although the unit is shielded against radio frequency and electromagnetic interference, extreme­ly high fields of RF and EMI should be avoided where possible.

0.4 Installation Recommendations

®

Getting

Started

®

Getting Started

Section 1

386

Getting Started

386 User Manual

2

Section 1

386

Power Switch

Turns the 386 on and off.

IEC Power Cord Receptacle

This is the power cord receptacle of the 386. An IEC cord is included with the shipped prod­uct.

AES/EBU Digital Connector

The 386 provides AES/EBU digital output formating through the XLR connector. Be sure to use short
lengths of 110Ω digital cables rather than standard XLR to XLR cables. Using the correct cables will
prevent digital dropouts and other interconnection problems.

S/PDIF Digital Connector

The 386 provides S/PDIF digital output formating through the RCA coaxial connector. Be sure to use
short lengths of 75Ω digital cables or 75Ω video cables rather than standard audio RCA to RCA
cables. Using the correct cables will prevent digital dropouts and other interconnection problems.

NOTE: Although digital information is coming out of both XLR and RCA jacks simultaneously, the correct format will only appear at the
output for the format type selected. For example, if you have AES/EBU format selected, an AES/EBU formatted signal will appear at
the output of both the XLR and the RCA connector. Or, if you have S/PDIF format selected, an S/PDIF formatted signal will appear at
the output of both the RCA and XLR connectors.

Sync In and Out Connectors

BNC connectors are provided for both clock in and out functions. The 386’s clock chips are dbx
custom VCXO chips, designed for low-jitter performance. You may use the 386 as a master
clock source, having other equipment slave to the 386, or you may slave the 386’s clock to any
other wordclock source device.

Analog Input Connectors

The analog input section of the 386 offers both XLR (Microphone) and a rear 1/4" TRS (Line)
electronically balanced connections. The 1/4” connector may be used in a balanced or unbal­anced configuration. Using a 1/4” TS connector will unbalance the signal.

Analog Output Connectors

The analog output section of the 386 offers both XLR and 1/4" TRS electronically balanced con­nections. The 1/4” connector may be used in a balanced or unbalanced configuration. Using a
1/4” TS connector will unbalance the signal.

Insert Jack

The 1/4” TRS Insert jack (Tip=SEND and Ring=RETURN), will allow you to add an effects loop
directly into the signal path of the 386. This insertion point is located after the tube section and
prior to the output section. This insertion positioning is ideal for adding external effects such
as a compressor or an EQ to the analog and digital output sections.

1.1 Rear Panel Connections

®

Instrument Input

This unbalanced high-impedance input connection is used to insert an instrument signal direct­ly into the preamp. Use the LINE switch to make instrument input or the rear panel line input
active. Plugging into the instrument jack will override the rear panel 1/4” input jack (line input
must be selected).

Line Select Switch

This switch, when lit, selects the rear line input or front panel instrument input (when some­thing is connected) as the source signal of the 386.

Drive Control

This control sets the amount of gain at the input of the vacuum tube stage. The range of gain
available is +30 to +60 dB (-15 to +15 dB when LINE INPUT is selected).

Peak LED

This LED will light 3dB prior to input stage clipping.

+48 Volt Switch

This switch activates phantom power for condenser microphones on pins 2 and 3 of the XLR
mic input. You should connect your microphone before turning on the phantom power to pre­vent damage to your microphone. Be sure to always lower levels prior to using the the +48
Volt Switch.

20db Pad Switch

This switch attenuates the microphone input signal by 20dB.

Phase Switch

This switch inverts the phase of the incoming signal at the Mic input by swapping pins 2 and
3 on the XLR connector.

Note- The +48 Volt, 20dB Pad and Phase functions are only available when the microphone input
is in use.

Low Cut Switch

This switch places a 12 dB per octave shelving high pass filter in the signal path. The knee
frequency of the Low Cut filter is 75 Hz. This filter is very useful for removing low frequency
rumble or handling noise from a microphone input signal.

Analog Output

This knob controls the overall level of the analog output signal, and ranges from -15 to +15dB.

1.2 Front Panel Controls

Getting Started

Section 1

386

386 User Manual

3

®