Symetrix 308 User Manual

308 VCA Volume Control/
Loudness EQ

USERN GUIDE

308 VCA Volume Control/Loudness
EQ User’s Guide

© July 2000 Symetrix, Inc.

All rights reserved.

Printed in the United States of America

Symetrix Part Number 53308-0A00

The information in this guide is subject to
change without notice. Symetrix, Inc. shall
not be liable for technical or editorial
errors or omissions contained herein; nor
is it liable for incidental or consequential
damages resulting from the furnishing,
performance, or use of this material.

Mention of third-party products is for in­formational purposes only and constitutes
neither an endorsement nor a recommen­dation. Symetrix assumes no responsibil­ity with regard to the performance or use
of these products.

Under copyright laws, no part of this user
guide may be reproduced or transmitted
in any form or by any means, electronic or
mechanical, without permission in writing
from Symetrix, Inc. If, however, your only
means of access is electronic, permission
to print one copy is hereby granted.
Permission to copy the Architects and
Engineers Specificiations for written
proposals specifying equipment for sound
reinforcement systems is, also, granted.

Symetrix, Inc.

6408 216th St. SW
Mountlake Terrace WA 98043

USA

Tel:[phone]
Fax:[phone]

Web: www.symetrixaudio.com

Email: [e-mail]

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Contents

Before You Begin 2

What Ships in the Box 2

Getting Help 2

Optional Rackmount Accessories 2

Notational Conventions in this User Guide 2

Operational Safety Summary 3

Equipment Markings 3

308 Product Information 4

Product Summary 4

Features 4

Making Hardware Connections 5

Overview of Rear Panel Connectors and Connections 5

Fast First-Time Setup 7

Controlling Channel Levels From a Potentiometer
or Voltage Ramp 8

Controlling Channel Levels by a Variable Resistor 9

Unbalanced Connections 10

Signal Flow Diagram 12

Troubleshooting 13

Hardware Specifications 14

Architects and Engineers Specifications 15

Warranty 16

Service 17

Declaration of Conformity 18

Input and Output Connector Wiring 11

1

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Before You Begin

| What Ships in the Box | Getting Help | Optional Rackmount Accessories | Notational

What Ships in the Box

 The 308 unit

 One PS-3 or PS-3E (export

version) power supply

 This user's guide

Conventions in this User Guide | Operator Safety Summary | Equipment Markings

Getting Help

If you have technical questions beyond the scope of this guide, please contact
our Technical Services Group in the following ways:

TUS customers

from 8:00 am to 4:30 pm Pacific Time Monday through Friday

F

[phone]

[e-mail]

www.symetrixaudio.com

[phone]

Optional Rackmount Accessories

MODEL IT E M DESCRIPTION

RM-3 19" Rackmount Tray IU in height

FP-3 Filler Panel Covers unused space when one 308

PY-3 Y Power Cable Connects a 308 with another 300 Series

RC-3 Remote Control For use with the 308 unit

Contact your dealer or Symetrix for purchasing information.

unit is mounted in the rack tray

product to the same power supply

Notational Conventions in this User Guide

Note Identifies information that needs extra emphasis. Generally

supplies extra information to help you to better use the 308.

CAUTION Identifies information that, if unheeded, may cause damage to

the 308 or other equipment in your system.

WARNING Identifies information that, if ignored, may be hazardous to

your health or that of others.

CAPS Controls, switches or other markings on the chassis of the 308.

2

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

AVIS:

NE PAS OUVRIR

Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.

SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.

S’adresser a un reparateur compétent.

RISQUE DE CHOC ELECTRIQUE

No user serviceable parts inside. Refer servicing to qualified service personnel.

CAUTION

WARNING:

TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE

DO NOT OPEN

RISK OF ELECTRIC SHOCK

Before You Begin

| Notational Conventions in this User Guide | Operator Safety Summary | Equipment Markings

| What Ships in the Box | Getting Help | Optional Rackmount Accessories

Operator Safety Summary

Follow all warnings and instructions.
Install in accordance with the
manufacturer’s instructions.

Power Source This product is intended
to operate from a Symetrix PS-3 or PS-3E
power supply.

Grounding The chassis of this product is
grounded through the grounding conduc­tor of the PS-3 or PS-3E power cord. To
avoid electric shock, plug the power cord
into a properly wired receptacle before
making any connections to the product. A
protective ground connection, by way of
the grounding conductor in the power
cord, is essential for safe operation. Do

not defeat the safety purpose of the
grounding plug. The grounding plug has

two blades and a third grounding prong.
The third prong is provided for your
safety. When the provided plug does not
fit your outlet, consult an electrician for
replacement of the obsolete outlet.

Danger from Loss of Ground If the
protective ground connection is lost, all
accessible conductive parts, including
knobs and controls that may appear to be
insulated, can render an electric shock.

Proper Power Cord Use only the power
cord and connector specified for the
product and your operating locale. Use
only a cord that is in good condition.
Protect the power cord from being walked
on or pinched, particularly at the plug,
convenience receptacle, and the point
where the cord exits from the apparatus.

Operating Location Do not operate this
equipment under any of the following
conditions: explosive atmospheres, in wet
locations, in inclement weather, improper
or unknown AC mains voltage, or if
improperly fused. Do not install near any
heat source such as radiators, heat
registers, stoves, or other apparatus
(including amplifiers) that produce heat.
Unplug this apparatus during lightning
storms or when unused for long periods of
time.

Stay Out of the Box To avoid personal
injury (or worse), do not remove the
product covers or panels. Do not operate
the product without the covers and panels
properly installed. Only use accessories
specified by the manufacturer. Clean only
with a damp cloth.

User-serviceable parts There are no
user serviceable parts inside the 308. In
case of failure, refer all servicing to the
factory. Servicing is required when the
308 has been damaged in any way, such
as when a power supply cord or plug is
damaged, liquid has been spilled or
objects have fallen into the apparatus, the
apparatus has been exposed to rain or
moisture, does not operate normally, or
has been dropped.

Equipment Markings

The lightning flash with arrowhead symbol
within an equilateral triangle is intended
to alert the user of the presence of
uninsulated “dangerous voltage” within
the product’s enclosure that may be of
sufficient magnitude to constitute a risk of
electric shock to persons. The exclamation
point within an equilateral triangle is
intended to alert the user of the presence
of important operating and maintenance
(servicing) instructions in the literature
accompanying the product (i.e., this user
guide).

CAUTION
To prevent electric shock, do not use the
polarized plug supplied with the unit
with any extension cord, receptacle, or
other outlet unless the blades can be
fully inserted.

3

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

308 Product Information

| Product Summary | Features

Product Summary

The Symetrix 308 VCA Volume

Control/Loudness EQ provides remote

level control and loudness EQ for

engineered sound systems. You set

the amount of loudness EQ compensa-

tion by adjusting rear panel EQ DEPTH

trimpots. These circuits may be

defeated entirely by turning the

trimpots fully counter-clockwise. The

308 is a half-rack unit that fits on a

shelf next to a mixer/amp or mounts

in a rack with optional Symetrix RM-3.

Features

Zone Operation Control the volume of a stereo signal

in a single zone or mono signals in
two zones.

Loudness EQ Circuit Enhances program frequency re-

sponse as volume is lowered.

Remote Level Control Volume control by use of Symetrix

RC-3 Remote Control, linear potenti­ometers* located up to 500 ft. from
unit, or DC control voltages of 0 to 10
volts range*. Stereo signals may be
adjusted by one control.

Audio Inputs & Outputs Rear-panel Euroblock connectors

accept balanced or unbalanced line­level signals.

*user supplied

4

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

Overview of Rear Panel Connectors and Controls

POWER

INPUT

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

RAMP1

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

CTL1

+10V

GND2

CTL2

EQ DEPTH AUDIO OUT

+24V

RAMP2GND1

GND

21

AUDIO INCONTROL

1

21

2

308

CONNECTION CONNECTOR TYPE WHAT IT DOES

POWER INPUT 7-pin DIN Connector Accepts power only from Symetrix

PS-3, PS-3E, or PY-3 power supply.

CONTROL Euroblock Connectors Input connections for remote controls.

PIN ASSIGNMENT

RAMP1 Ramp Output #1 Same control voltage applied to CTL1

appears here. Use it for controlling
channel 1 of multiple 308 units.

CTL1 Control Input #1 Connect a ramp voltage or the wiper

(W) of a 10k ohm linear taper poten­tiometer here for controlling channel
1 audio levels.

GND1 Control 1 Ground Connect the ramp voltage ground or

the CCW (low) terminal of the pot
connected to CTL1 here.

+10V +10 VDC Output Provides the +10 VDC control voltage

for 10k ohm linear taper
potentiometer(s). Connect the pot
terminal CW (high) here. If using a
control pot for each channel, connect
the CW terminals from two pots here.

GND2 Control 2 Ground Connect the ramp voltage ground or

the CCW (low) terminal of a 10k ohm
linear taper potentiometer here for
controlling channel 2 audio levels.

CTL2 Control Input #2 Connect a ramp voltage or the wiper

(W) of the pot connected to GND2
here.

RAMP2 Ramp Output #2 Same control voltage applied to CTL2

appears here. Use it for controlling
channel 2 of multiple 308 units.

GND Ground Provides ground connection for +24

+24V +24 VDC Output Provides +24 VDC power for remote

VDC connections.

controls requiring it.

5

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

Overview of Rear Panel Connectors and Controls continues

CONNECTION CONNECTOR TYPE WHAT IT DOES

EQ DEPTH Trimpots 1 and 2 Controls the amount of loudness EQ

compensation applied to their respec­tive audio channels. They are set for
maximum loudness contour from the
factory (maximum mid-range attenu­ation). Can be independently ad­justed. Once adjusted, the amount of
EQ compensation follows the volume
set by the remote controls.

At full volume (+10V control
voltage), the EQ response is flat and
the 308 gain is at unity (the 308 will
not add gain to your system).

At lowered volume, the midrange
response is reduced to a maximum of
–15 dB @ 1 kHz, effectively boosting
the bass and treble frequencies.

Turning these trimpots counterclock­wise lessens the amount of loudness
EQ compensation.

Turning these trimpots fully counter­clockwise turns off the EQ DEPTH
feature.

AUDIO OUT Euroblock Connectors Provides balanced line-level audio

output signals for their respective
channels. Use 2-conductor shielded
cable for all connections.*

AUDIO IN Euroblock Connectors Connect balanced line-level input

signals to these connectors for their
respective channels. Use 2-conductor
shielded cable for all connections.*

*For balanced use, the 308 follows

AES standards for balanced audio
circuits.

For unbalanced use, see in this
section:

Unbalanced Connections

Input and Output Connector Wiring

6

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels

By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

Fast First-Time Setup

1 Connect your line-level audio

inputs and outputs to the

AUDIO IN and AUDIO OUT

Euroblock connectors.

2 Connect your remote controls to

the CONTROL Euroblock connec-

tors. (If using a potentiometer,
see in this section, Controlling
Both Channels from a Single
Potentiometer. If using a
rheostat, see Controlling Channel
Levels By a Variable Resistor.)

3 Connect the external power

supply to the 308 unit, then
plug the power supply into an
AC outlet.

4 Apply line-level audio signal to

the inputs.

5 Adjust the remote controls to

maximum level. Then set your
system power amp levels to the
desired maximum level. As you
adjust the remote controls, the
308 passes audio signals. At full
volume setting, the 308 is at
unity gain.

6 Turn down the remote controls

to the lowest listening level you
expect the system to be oper­ated at.

7 The EQ DEPTH trimpots are set

for maximum loudness contour
from the factory. At the lowest

VCA setting, the EQ DEPTH is

–15 dB @ 1k. Adjust the trimpots
counterclockwise if you want
less EQ response. To turn off
this feature, turn the trimpots
completely counterclockwise.

Basic Remote Setup Showing One Channel

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

POWER

INPUT

CHANNEL 1

Control Voltage
0 to 10V

Ramp Generator GND
0 to 10V

Volume

SYMETRIX RC-3 REMOTE CONTROL PIN CONNECTION
TO THE 308 PINS

RC-3 Pins 308 Channel 1 Pins 308 Channel 2 Pins

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

+10V +10V +10V

CTL CTL1 CTL2

GND GND1 GND2

RAMP1

Symetrix RC-3 Remote Control

CTL1

+10V

GND2

RAMP2GND1

CTL2

GND

+24V

 Fast Setup is complete.

EQ DEPTH AUDIO OUT

21

GND
CTL
+10

AUDIO INCONTROL

2

121

308

RAMP/CONTROL VOLTAGE PIN CONNECTION TO THE 308 PINS

Device Pins 308 Channel 1 Pins 308 Channel 2 Pins

Ramp generator GND GND1 GND2

Control voltage CTL1 CTL2

7

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel

Levels By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

Controlling Channel Levels From a Potentiometer or Voltage Ramp

Setup for Remote Control

Connect the potentiometers to the

CONTROL Euroblock connectors. Its

pots must be 10k ohms linear taper,
and the cable should be 2-conductor
with shield. You can locate the
potentiometers up to 500 feet from
the 308 unit. Stereo signals can be
adjusted by using one potentiometer.

To use two potentiometers to control each channel

EQ DEPTH AUDIO OUT

+24V

GND

CCW

CW

CW

CCW

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

POWER

INPUT

CHANNEL 1

Control Voltage

Ramp Generator GND

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

RAMP1

CTL1

+10V

GND2

RAMP2GND1

CTL2

21

CHANNEL 2

Control Voltage

Ramp Generator GND

Potentiometer

WW

AUDIO INCONTROL

2

121

308

To use one potentiometer to control both channels

EQ DEPTH AUDIO OUT

+24V

21

Jumper connects RAMP1 and CTL2

POWER

INPUT

CHANNELS 1 and 2

Control Voltage

Ramp Generator GND

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

Potentiometer

CW

W

CCW

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

RAMP1

CTL1

+10V

GND2

RAMP2GND1

CTL2

GND

POTENTIOMETER PIN CONNECTION TO THE 308 PINS

Potentiometer Pins 308 Channel 1 Pins 308 Channel 2 Pins

CW (high) +10V +10V

W (Wiper) CTL1 CTL2

AUDIO INCONTROL

2

121

308

CCW (low) GND1 GND2

8

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel

Levels By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

Controlling Channel Levels By a Variable Resistor (ie., a rheostat)

Setup for Remote Output Mute

This setup provides compatibility with
certain remote volume control panels.
A resistance of 10K ohms results in
unity gain. A resistance of 0 ohms
(short circuit) results in maximum
attenuation. You do not need a
connection to the +10V terminal.

Use this setup when you need a
remote output mute. Connecting a
normally-open mute push button or
relay contact in parallel with the
control resistance results in maximum
attenuation when the switch contacts
are closed. The 308 is not damaged
by such a connection.

To use two rheostats to control each channel

POWER

INPUT

CHANNEL 1

Mute

CCW

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

RAMP1

CTL1

+10V

GND2

RAMP2GND1

CTL2

GND

+24V

CHANNEL 2

Mute

EQ DEPTH AUDIO OUT

21

Rheostat

CCW

WW

AUDIO INCONTROL

2

121

308

To use one rheostat to control both channels

EQ DEPTH AUDIO OUT

+24V

21

Jumper connects RAMP1 and CTL2

POWER

INPUT

CHANNELS 1 and 2

CONNECT TO
SYMETRIX
PS-3 OR PS-3E
POWER
SUPPLY ONLY.

Mute

Rheostat

W

CCW

(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)

RAMP1

CTL1

+10V

GND2

RAMP2GND1

CTL2

GND

RHEOSTAT PIN CONNECTION TO THE 308 PINS

Rheostat Pins 308 Channel 1 Pins 308 Channel 2 Pins

W (Wiper) CTL1 CTL2

AUDIO INCONTROL

2

121

308

CCW (low) GND1 GND2

9

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels

By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

Unbalanced Connections

We do not recommend unbalanced
input and output connections, but
follow these instructions if you must
do so.

Unbalanced Audio Output Connections

1 Connect the (+) terminal of the 308 to the (+ or high) of the unbalanced

input connector.

2 Make no connection to the (–) terminal of the 308.

3 Connect the cable shield to the ground of the 308 and at the unbalanced

input connector.

Notes
The output signal level of the 308 will be 6 dB lower when driving an unbalanced

input without a transformer or matching interface device. To avoid this, use the
Symetrix 303 Interface Amplifier or 307 Dual Isolation Transformer.

If you experience hum or noise, make sure that both the 308 and the device with
the unbalanced input are grounded on the same AC mains circuit. If this is not the
source of the noise problem, isolate the balanced output from the unbalanced
input using the Symetrix 303 or 307.

Unbalanced Audio Input Connections

1 Connect the incoming signal (+ or high) to the (+) terminal of the 308.

2 Connect the incoming signal ground to the (–) terminal of the 308.

3 Connect the cable shield to the ground connection of the 308 only

(leave the other end unconnected).

Notes
The 308 is designed to operate at the +4 dBu level. If the unbalanced output(s) of

the device feeding the 308 is –10 dBV (semi-pro or consumer level), use the
Symetrix 303 Interface Amplifier to convert the unbalanced source to a balanced
signal, and boost the –10 dBV signal to the +4 dBu level.

If you experience hum or noise, make sure that both the 308 and the device with
the unbalanced output are grounded on the same AC mains circuit. If this is not
the source of the noise problem, isolate the balanced input from the unbalanced
output using a Symetrix 303 or 307.

10

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Making Hardware Connections

| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels

By a Variable Resistor | Unbalanced Connections | Input and Output Connector Wiring

| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup

Input and Output Connector Wiring

METHOD CONNECTOR CHANNEL

Balanced Terminal Strip

Balanced Female XLR

Pin 1 = Circuit Ground
Pin 2 = High
Pin 3 = Low

21 3

Input

Input

Input

Balanced TRS Plug

Tip = High
Ring = Low
Sleeve = Shield

Unbalanced TS Plug

Tip = High
Sleeve = Low + Shield

Unbalanced RCA Plug

Tip = High
Sleeve = Low
Cable Shield = Not Connected

Balanced Male XLR

Pin 1 = Circuit Ground
Pin 2 = High
Pin 3 = Low

TIP

TIP

RING

SLEEVE

SLEEVE

12 3

Input

Input

Output

Output

Unbalanced TS Plug

Tip = High
Sleeve = Shield
Wire Low = Not Connected

TIP

SLEEVE

11

BALANCED
INPUT

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Signal Flow Diagram

SUBTRACT

LEVEL
VCA

BALANCED
OUTPUT

DEPTH

REMOTE

CONTROL

RAMP

OUT

10V REF

EQ VCA
DC CONTROL

LEVEL VCA
DC CONTROL

EQ
VCA

BANDPASS
FILTER

12

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Troubleshooting

SYMPTOM PROBABLE CAUSE/WHAT TO DO

No output Check cables and connections to see if:

• Inputs are driving outputs, and outputs are driving inputs.

• That there is a signal from the source and that it is getting to the 308.

Check if unit is plugged in.

Hum or buzz in output Check input and output connector wiring.

Check for ground loop problem. Inspect related system equipment ground­ing to see that all system components are on the same AC ground.

Distortion Check input signal.

Check if line input signal may be too hot.

If using a high setting for your maximum audio level, you may be overload­ing the input to your amplifier; lower the audio level.

Check if something else is clipping in the signal chain.

Noise (hiss) Check input signal levels. The 308 is intended to operate at or near “line”

level (+4dBu is nominal). Make sure that the signal you are feeding to the
308 is a line level signal, not mic level.

Check that all systems components are on the same AC ground.

Check gain settings on upstream equipment. The system gain structure
should be such that the 308 receives +4dBu nominal signal.

No LED display Check if unit is plugged in.

Verify that AC outlet works.

13

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Hardware Specifications

Input/Output

Maximum Input Level +20 dBu balanced, +20 dBu unbalanced
Maximum Output Level +22 dBu balanced, +18 dBu unbalanced
Input Impedance >20k ohms balanced, >10k ohms unbalanced
Output Impedance 200 ohms balanced, 100 ohms unbalanced
Input Common Mode Rejection >40 dB

Performance Data

Frequency Response 20 Hz to 20 kHz +0, – 0.5 dB

(with no equalization applied)

20 Hz to 20 kHz +0, –1.5 dB (at unity gain with max EQ depth)
THD+N <0.025% at unity gain, 0 dBu in/out
Residual Output Noise – 95 dBu typical at unity gain
Gain Control 0 dB (unity) to – 65 dB
Equalization –15 dB max @ 1 kHz

Analog Control

Control inputs accept any of (a) 10k linear rheostat to ground

(b) 10k linear potentiometer from +10 reference output to ground

(c) 0 to 10 VDC control voltage

(d) Symetrix RC-3 Remote Control

Gain Unity at +10 VDC and max attenuation at 0 VDC
Ramp Out Buffered duplicate of the Control In voltage

Auxiliary Power Out +24 VDC ±10%, 100 milliamps max continuous load

Connections

Inputs, Outputs, Control Ports Euroblock
AC Power In 7-pin DIN

Physical

Size (H x W x D) 1/2 rack unit

1.75 in. x 8.5 in. x 6.5 in. / 4.445 cm x 21.59 cm x 15.875 cm

Shipping Weight 4.5 lbs.

Electrical

Power Requirements 12W maximum, Symetrix PS-3 or PS-3E only
PS-3 115V, 60 Hz AC nominal
PS-3E 230V, 50 to 60 Hz AC nominal

In the interest of continuous product
improvement, Symetrix, Inc. reserves
the right to alter, change, or modify
these specifications without prior
notice.

14

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Architects and Engineers Specifications

The VCA volume control / loudness EQ
shall provide two channels of remote
level adjustment and automatic
loudness EQ compensation for
controlling a stereo signal in one zone
or mono signals in two zones. There
shall be a voltage controlled amplifier
(VCA) in each channel controlled by
either a 0 to 10 VDC ramp signal or
by a 10k ohms linear taper potenti­ometer or other compatible remote
control, such as the Symetrix RC-3.
Potentiometers may be located up to
500 feet from the VCA volume
controller. The loudness EQ will be
flat at full volume and the output gain
will be at unity. At lower volumes, the
loudness EQ shall automatically
effectively boost the bass and treble
frequencies by lowering the midrange
response. The maximum midrange
attenuation will be –15 dB @ 1 kHz.

The VCA volume control / loudness EQ
shall provide two balanced line-level
audio inputs on Euroblock connectors.
The input impedance shall be at least
20k ohms balanced, 10k ohms
unbalanced. The maximum input level
shall be +20 dBu balanced, +20 dBu
unbalanced. There shall be two
balanced line-level audio outputs on
Euroblock connectors. The output
impedance shall be 400 ohms bal­anced, 200 ohms unbalanced. The
maximum output level shall be +22
dBu balanced, +18 dBu unbalanced.

Screwdriver adjustable trimpots shall
be provided for selecting the amount
of loudness EQ compensation for each
channel. Nine inputs for remote
control connections shall also be
provided on Euroblock connectors.
These inputs shall consist of: Ramp
Out, Control In, Ground for each
channel; +10 VDC Out; Ground; +24
VDC Out.

A front panel power indicator shall be
provided.

The frequency response shall be +0,
–0.5 dB, measured between 20 Hz
and 20 kHz. THD+N shall be less than

0.025% measured at unity gain.
Power consumption shall be 12W
maximum.

The unit shall occupy half of the width
of one rack space. The physical
dimensions shall be 1.75 in. (H) x 8.5
in. (W) x 6.5 in. (D) / 4.445 cm (H) x

21.59 cm (W) x 15.875 cm (D).

The VCA volume control / loudness EQ
shall operate by means of a Symetrix
PS-3 connected to 115 VAC nominal,
(95–130 VAC), 60 Hz or a Symetrix
PS-3E connected to 230 VAC nominal,
(165–255 VAC), 50 to 60 Hz.

The VCA volume control / loudness EQ
shall be a Symetrix model 308 VCA
Volume Control / Loudness EQ.

15

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Warranty

Following are the terms and limitations of
the Symetrix warranty.

Warranty

Symetrix, Inc. expressly warrants to the
original purchaser (“Buyer”), subject to the
terms and conditions set forth below, that
the Product will be free from defects in
material and workmanship as a result of
normal commercial use for one (1) year
from the date of purchase.

Symetrix’s warranty obligation is limited to
the repair, replacement, or refund at
Symetrix’s sole discretion, of the part or
parts of the Product which may thus prove
defective in materials or workmanship
within one year from date of purchase
under normal use and which our examina­tion discloses to our satisfaction to be thus
defective, provided that Buyer gives
Symetrix prompt notice of its warranty
claim and satisfactory proof thereof.

Symetrix will make every reasonable effort
to ensure that parts are available to
support the repair of our products under
warranty. In the event that a product or
component part thereof becomes obsolete,
unavailable or irreparable, Symetrix
reserves the right to refund a prorated
portion of the purchase price in full
satisfaction of all warranty claims.

In order to serve you better we request
that the Buyer shall, prior to shipping
Product to Symetrix for warranty service,
contact Symetrix and secure a Return
Authorization Number that shall be
included with the returned Product. This
will facilitate our efforts to keep track of
your Product and process your warranty
repair as quickly as possible. Buyer will
prepay all freight charges to ship the
Product to Symetrix for warranty inspection
and service. This warranty is subject to
Symetrix’s inspection of the Product at its
facilities and, upon Symetrix’s request,
satisfactory proof of purchase (dated copy
of original retail dealer’s invoice.)

Symetrix reserves the right to effect
repairs to the product with reconditioned
components/parts. Products once repaired
under warranty will be shipped to Buyer
freight prepaid by Symetrix via United
Parcel Service (surface) or any similar
shipper, to any location designated by

buyer within the Continental United States.
At Buyer’s request and expense Product
will be returned via airfreight. Outside the
continental United States, repaired or
replaced products will be returned freight
collect.

THIS WARRANTY IS EXPRESSLY IN LIEU OF
ALL OTHER WARRANTIES EXPRESS OR
IMPLIED, ARISING BY LAW OR OTHERWISE
(INCLUDING, WITHOUT LIMITATION ANY
OBLIGATIONS OF THE SELLER WITH
RESPECT TO CONSEQUENTIAL DAMAGES)
INCLUDING THE WARRANTIES OF MER­CHANTABILITY AND FITNESS FOR USE
AND OF ALL OTHER OBLIGATIONS OR
LIABILITIES ON OUR PART, AND WE
NEITHER ASSUME, NOR AUTHORIZE ANY
OTHER PERSON TO ASSUME FOR US, ANY
OTHER LIABILITY IN CONNECTION WITH
THE SALE OF THE PRODUCT. THIS
WARRANTY SHALL NOT APPLY TO THIS
PRODUCT OR ANY PART THERE OF WHICH
HAS BEEN SUBJECT TO ACCIDENT,
NEGLIGENCE, ALTERATION, ABUSE, OR
MISUSE. WE MAKE NO WARRANTY
WHATSOEVER IN RESPECT TO ACCESSO­RIES OR PARTS NOT SUPPLIED BY US. THE
TERM “ORIGINAL PURCHASER,” AS USED
IN THIS WARRANTY SHALL BE DEEMED TO
MEAN THAT PERSON OR COMPANY THAT
ORIGINALLY PURCHASED THE PRODUCT.

This Symetrix product has been designed
and manufactured for use in professional/
industrial systems and is not intended for
other usage. This warranty only applies to
Buyers using the Product in professional/
industrial systems. With respect to others,
including but not limited to consumers for
personal, family, or household use,

Symetrix expressly disclaims all
warranties, including but not limited to
warranties of merchantability and
fitness for a particular purpose and the
express warranties as otherwise
provided herein.

Symetrix reserves the right to modify the
design or make additions to, or improve­ments to, its product lines without making
similar upgrades to Product purchased by
Buyer. Symetrix does not authorize any
third party, including any dealer or sales
representative, to assume any liability,
effect any repairs or modifications to the
Product, or make any additional warranties
or representation regarding the Product or
Product information on behalf of Symetrix.

Symetrix’s total liability on any claim,
whether in contract, tort (including
negligence) or otherwise arising out of,
connected with, or resulting from the
manufacture, sale, delivery, resale, repair,
replacement or use of Product will not
exceed the purchase price of the Product or
any part thereof which gives rise to the
claim. In no event will Symetrix be liable
for any incidental or consequential
damages including but not limited to
damage for lost revenue, cost of capital,
claims of customers for service interrup­tions or failure to supply, and costs and
expenses incurred in connection with labor,
overhead, transportation, installation or
removal of products or substitute facilities
or supply houses as a result of Product
failure.

This limited warranty gives Buyer certain
rights. Buyer may have additional rights
under applicable law.

16

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Service

Servicing the 308

If you have determined that your unit requires repair services and you live outside of the United States, please contact your
local Symetrix dealer or distributor for instructions on how to obtain service. If you reside in the U.S. then proceed as follows:

Before sending anything to Symetrix, contact our Customer Service Department for a return authorization (RA) number. The
telephone number is (425) 78-7728 or email: [e-mail]

In-warranty Repairs

To get your Symetrix product repaired under the terms of the warranty:

1. Call us for an RA number.

2. Pack the unit in its original packaging materials.

3. Include your name, address, daytime telephone number, and a brief
statement of the problem.

4. Write the RA number on the outside of the box.

5. Ship the unit to Symetrix, freight prepaid.

We do not accept freight collect shipments.

Repairs made in-warranty will cost you only one-way freight charges. We ll prepay the return (surface) freight.

If you send us your product in substandard packaging, we will charge you for factory shipping materials. If you don t have the
factory packaging materials, please use an oversized carton, wrap the unit in a plastic bag, and surround it with bubble-wrap.
Pack the box full of Styrofoam peanuts. Be sure there is enough clearance in the carton to protect the rack ears (you wouldn t
believe how many units are returned with bent ears). We will return the unit in Symetrix packaging. Of course, if the repair is
due to operator error, parts and labor will be charged. In any event, if there are charges for the repair costs, you will pay for the
return freight. All charges will be COD unless you have made other arrangements (prepaid, Visa or Mastercard).

Out-of-warranty Repairs

If the warranty period has passed, you ll be billed for all necessary parts, labor, packaging materials, and freight charges.
Please remember, you must call for an RA number before sending the unit to Symetrix.

17

Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide

Declaration of Conformity

We, Symetrix, Inc.

6408 216th St. SW, Mountlake Terrace, Washington USA

declare under our sole responsibility that the product:

308 VCA Volume Control/Loudness EQ

to which this declaration relates, is in conformity with the following standard:

EN 55103-2
Electromagnetic Compatibility—Product Family Standard for Audio, Video, and

Entertainment Lighting Control Apparatus for Professional Use
Part 2: Immunity

PS-3E power supply complies with this code:

EN 60065

Safety Requirements for Mains Operated Electronic and Related Apparatus for
Household and Similar General Use

The technical construction file is maintained at:

Symetrix, Inc.

6408 216th St. SW
Mountlake Terrace, WA 98037-2303

USA

The authorized representative located within the European Community is:

World Marketing Associates

P.O. Box 100

St. Austell, Cornwall, PL26 6YU, UK

Date of issue: May 30, 2000

Place of issue: Mountlake Terrace, Washington USA

Authorized signature:

Dane Butcher, President

18

Symetrix, Inc.

6408 216th St. SW

Mountlake Terrace, WA 98043

USA

Tel: [phone]

Fax: [phone]

Web site: http://www.symetrixaudio.com

Email: [e-mail]