Symetrix 308 User manual

308 VCA Volume Control/
Loudness EQ
USERNGUIDE

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 umber 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 in-
formational purposes only and constitutes
neither an endorsement nor a recommen-
dation. Symetrix assumes no responsibil-
ity 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: [email protected]

1
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Before You Begin 2
What Ships in the Box 2
Getting Help 2
Optional Rackmount Accessories 2
Notational Conventions in this User Gui e 2
Operational Safety Summary 3
Equipment Markings 3
308 Product Information 4
Pro uct Summary 4
Features 4
Making Hardware Connections 5
Overview of Rear Panel Connectors an 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
Unbalance Connections 10
Input an Output Connector Wiring 11
Contents
Signal Flow Diagram 12
Troubleshooting 13
Hardware Specifications 14
Architects and Engineers Specifications 15
Warranty 16
Service 17
Declaration of Conformity 18

2
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Before You Begin
What Ships in the Box
The 308 unit
One PS-3 or PS-3E (export
version) power supply
This user's gui e
Getting Help
If you have technical questions beyon the scope of this gui e, please contact
our Technical Services Group in the following ways:
TUS customers [phone]
from 8:00 am to 4:30 pmPacific Time Monday through Friday
F [phone]
tech@symetrixau io.com
www.symetrixau io.com
Optional Rackmount Accessories
MODEL ITEM DESCRIPTION
RM-3 19" Rackmount Tray IU in height
FP-3 Filler Panel Covers unused space when one 308
unit is mounted in the rack tray
PY-3 Y Power Cable Connects a 308 with another 300 Series
product to the same power supply
RC-3 Remote Control For use with the 308 unit
Contact your ealer or Symetrix for purchasing information.
Notational Conventions in this User Guide
Note I entifies information that nee s extra emphasis. Generally
supplies extra information to help you to better use the 308.
CAUTION I entifies information that, if unhee e , may cause amage to
the 308 or other equipment in your system.
WARNING I entifies information that, if ignore , may be hazar ous to
your health or that of others.
CAPS Controls, switches or other markings on the chassis of the 308.
| What Ships in the Box | Getting Help | Optional Rackmount Accessories | Notational
Conventions in this ser Guide | Operator Safety Summary | Equipment Markings

3
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
Operator Safety Summary
Follow all warnings an instructions.
Install in accor ance with the
manufacturer’s instructions.
Power Source This pro uct is inten e
to operate from a Symetrix PS-3 or PS-3E
power supply.
Grounding The chassis of this pro uct is
groun e through the groun ing con uc-
tor of the PS-3 or PS-3E power cor . To
avoi electric shock, plug the power cor
into a properly wire receptacle before
making any connections to the pro uct. A
protective groun connection, by way of
the groun ing con uctor in the power
cor , is essential for safe operation. Do
not defeat the safety purpose of the
grounding plug. The groun ing plug has
two bla es an a thir groun ing prong.
The thir prong is provi e for your
safety. When the provi e plug oes not
fit your outlet, consult an electrician for
replacement of the obsolete outlet.
Danger from Loss of Ground If the
protective groun connection is lost, all
accessible con uctive parts, inclu ing
knobs an controls that may appear to be
insulate , can ren er an electric shock.
Proper Power Cord Use only the power
cor an connector specifie for the
pro uct an your operating locale. Use
only a cor that is in goo con ition.
Protect the power cor from being walke
on or pinche , particularly at the plug,
convenience receptacle, an the point
where the cor exits from the apparatus.
Operating Location Do not operate this
equipment un er any of the following
con itions: explosive atmospheres, in wet
locations, in inclement weather, improper
or unknown AC mains voltage, or if
improperly fuse . Do not install near any
heat source such as ra iators, heat
registers, stoves, or other apparatus
(inclu ing amplifiers) that pro uce heat.
Unplug this apparatus uring lightning
storms or when unuse for long perio s of
time.
Stay Out of the Box To avoi personal
injury (or worse), o not remove the
pro uct covers or panels. Do not operate
the pro uct without the covers an panels
properly installe . Only use accessories
specifie by the manufacturer. Clean only
with a amp cloth.
ser-serviceable parts There are no
user serviceable parts insi e the 308. In
case of failure, refer all servicing to the
factory. Servicing is require when the
308 has been amage in any way, such
as when a power supply cor or plug is
amage , liqui has been spille or
objects have fallen into the apparatus, the
apparatus has been expose to rain or
moisture, oes not operate normally, or
has been roppe .
Equipment Markings
The lightning flash with arrowhea symbol
within an equilateral triangle is inten e
to alert the user of the presence of
uninsulate “ angerous voltage” within
the pro uct’s enclosure that may be of
sufficient magnitu e to constitute a risk of
electric shock to persons. The exclamation
point within an equilateral triangle is
inten e to alert the user of the presence
of important operating an maintenance
(servicing) instructions in the literature
accompanying the pro uct (i.e., this user
gui e).
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.
| What Ships in the Box | Getting Help | Optional Rackmount Accessories
| Notational Conventions in this User Gui e | Operator Safety Summary | Equipment Markings
Before You Begin

4
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
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 lowere .
Remote Level Control Volume control by use of Symetrix
RC-3 Remote Control, linear potenti-
ometers* locate up to 500 ft. from
unit, or DC control voltages of 0 to 10
volts range*. Stereo signals may be
a juste by one control.
Audio Inputs & Outputs Rear-panel Euroblock connectors
accept balance or unbalance line-
level signals.
*user supplied
| Product Summary | Features
308 Product Information

5
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Overview of Rear Panel Connectors and Controls
2
308
EQ DEPTH AUDIO OUT 1
21
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT
SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
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 applie 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 poten-
tiometer here for controlling channel
1 au io levels.
GND1 Control 1 Groun Connect the ramp voltage groun or
the CCW (low) terminal of the pot
connecte to CTL1 here.
+10V +10 VDC Output Provi es 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 Groun Connect the ramp voltage groun or
the CCW (low) terminal of a 10k ohm
linear taper potentiometer here for
controlling channel 2 au io levels.
CTL2 Control Input #2 Connect a ramp voltage or the wiper
(W) of the pot connecte to GND2
here.
RAMP2 Ramp Output #2 Same control voltage applie to CTL2
appears here. Use it for controlling
channel 2 of multiple 308 units.
GND Groun Provi es groun connection for +24
VDC connections.
+24V +24 VDC Output Provi es +24 VDC power for remote
controls requiring it.
| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels
By a Variable Resistor | Unbalance Connections | Input an Output Connector Wiring
Making Hardware Connections

6
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Overview of Rear Panel Connectors and Controls continues
CONNECTION CONNECTOR TYPE WHAT IT DOES
EQ DEPTH Trimpots 1 an 2 Controls the amount of lou ness EQ
compensation applie to their respec-
tive au io channels. They are set for
maximum lou ness contour from the
factory (maximum mi -range attenu-
ation). Can be in epen ently a -
juste . Once a juste , the amount of
EQ compensation follows the volume
set by the remote controls.
At full volume (+10V control
voltage), the EQ response is flat an
the 308 gain is at unity (the 308 will
not a gain to your system).
At lowered volume, the mi range
response is re uce to a maximum of
–15 B @ 1 kHz, effectively boosting
the bass an treble frequencies.
Turning these trimpots counterclock-
wise lessens the amount of lou ness
EQ compensation.
Turning these trimpots fully counter-
clockwise turns off the EQ DEPTH
feature.
AUDIO OUT Euroblock Connectors Provi es balance line-level au io
output signals for their respective
channels. Use 2-con uctor shiel e
cable for all connections.*
AUDIO IN Euroblock Connectors Connect balance line-level input
signals to these connectors for their
respective channels. Use 2-con uctor
shiel e cable for all connections.*
*For balanced use, the 308 follows
AES stan ar s for balance au io
circuits.
For unbalanced use, see in this
section:
Unbalance Connections
Input an Output Connector Wiring
Making Hardware Connections
| Overview of Rear Panel Connectors and Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels
By a Variable Resistor | Unbalance Connections | Input an Output Connector Wiring

7
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Basic Remote Setup Showing One Channel
Fast First-Time Setup
1Connect your line-level au io
inputs an outputs to the
AUDIO IN an AUDIO OUT
Euroblock connectors.
2Connect 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.)
3Connect the external power
supply to the 308 unit, then
plug the power supply into an
AC outlet.
4Apply line-level au io signal to
the inputs.
5A just the remote controls to
maximum level. Then set your
system power amp levels to the
esire maximum level. As you
a just the remote controls, the
308 passes au io signals. At full
volume setting, the 308 is at
unity gain.
6Turn own the remote controls
to the lowest listening level you
expect the system to be oper-
ate at.
7The EQ DEPTH trimpots are set
for maximum lou ness contour
from the factory. At the lowest
VCA setting, the EQ DEPTH is
–15 B @ 1k. A just the trimpots
counterclockwise if you want
less EQ response. To turn off
this feature, turn the trimpots
completely counterclockwise.
Fast Setup is complete.
Making Hardware Connections
2
308
EQ DEPTH AUDIO OUT
121
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT
SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
Control Voltage
0 to 10V
Ramp Generator GND
0 to 10V
CHANNEL 1
+10
GND
CTL
Volume
SYMETRIX RC-3 REMOTE CONTROL PIN CONNECTION
TO THE 308 PINS
RC-3 Pins 308 Channel 1 Pins 308 Channel 2 Pins
+10V +10V +10V
CTL CTL1 CTL2
GND GND1 GND2
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
Symetrix RC-3 Remote Control
| Overview of Rear Panel Connectors an Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels
By a Variable Resistor | Unbalance Connections | Input an Output Connector Wiring

8
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
2
308
EQ DEPTH AUDIO OUT
121
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
CCW
CW
W
Control Voltage
Ramp Generator GND
Potentiometer
CHANNELS 1 and 2
Controlling Channel Levels From a Potentiometer or Voltage Ramp
Making Hardware Connections
2
308
EQ DEPTH AUDIO OUT
121
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
CCW
CCW
CW
CW
WW
Control Voltage
Ramp Generator GND
Control Voltage
Ramp Generator GND
Potentiometer
CHANNEL 1 CHANNEL 2
To use two potentiometers to control each channel
To use one potentiometer to control both channels
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
CCW (low) GND1 GND2
Jumper connects RAMP1 and CTL2
Setup for Remote Control
Connect the potentiometers to the
CONTROL Euroblock connectors. Its
pots must be 10k ohms linear taper,
an the cable shoul be 2-con uctor
with shiel . You can locate the
potentiometers up to 500 feet from
the 308 unit. Stereo signals can be
a juste by using one potentiometer.
| Overview of Rear Panel Connectors an Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel
Levels By a Variable Resistor | Unbalance Connections | Input an Output Connector Wiring

9
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Controlling Channel Levels By a Variable Resistor (ie., a rheostat)
2
308
EQ DEPTH AUDIO OUT
121
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
CCW
CCW
WW
Mute
Rheostat
CHANNEL 1 CHANNEL 2
Mute
2
308
EQ DEPTH AUDIO OUT
121
21
AUDIO INCONTROL
GND
+24V
GND2
CTL2
RAMP2GND1
CTL1
RAMP1
(VOLUME CONTROL POTS 10K OHMS LINEAR TAPER)
+10V
POWER
INPUT SYMETRIX
CONNECT TO
SUPPLY ONLY.
PS-3 OR PS-3E
POWER
Mute
CCW
W
Rheostat
CHANNELS 1 and 2
Setup for Remote Output Mute
This setup provi es 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 o not nee a
connection to the +10V terminal.
Use this setup when you nee 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 close . The 308 is not amage
by such a connection.
To use two rheostats to control each channel
To use one rheostat to control both channels
Making Hardware Connections
RHEOSTAT PIN CONNECTION TO THE 308 PINS
Rheostat Pins 308 Channel 1 Pins 308 Channel 2 Pins
W (Wiper) CTL1 CTL2
CCW (low) GND1 GND2
Jumper connects RAMP1 and CTL2
| Overview of Rear Panel Connectors an Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel
Levels By a Variable Resistor | Unbalance Connections | Input an Output Connector Wiring

10
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Unbalanced Connections
We o not recommen unbalance
input an output connections, but
follow these instructions if you must
o so.
Unbalanced Audio Output Connections
1Connect the (+) terminal of the 308 to the (+ or high) of the unbalance
input connector.
2Make no connection to the (–) terminal of the 308.
3Connect the cable shiel to the groun of the 308 an at the unbalance
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
1Connect the incoming signal (+ or high) to the (+) terminal of the 308.
2Connect the incoming signal groun to the (–) terminal of the 308.
3Connect the cable shiel to the groun connection of the 308 only
(leave the other en unconnecte ).
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.
Making Hardware Connections
| Overview of Rear Panel Connectors an Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels
By a Variable Resistor | nbalanced Connections | Input an Output Connector Wiring

11
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
METHOD CONNECTOR CHANNEL
Input and Output Connector Wiring
Making Hardware Connections
| Overview of Rear Panel Connectors an Controls | Fast First-Time Setup
| Controlling Channel Levels From a Potentiometer or Voltage Ramp | Controlling Channel Levels
By a Variable Resistor | Unbalance Connections | Input and Output Connector Wiring
TIP
SLEEVE
Output
Output
Input
12 3
Input
TIP
SLEEVE
Input
Input
TIP
SLEEVE
RING
Input
21 3
Balanced Terminal Strip
Balanced Female XLR
Pin 1 = Circuit Ground
Pin 2 = High
Pin 3 = Low
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
Unbalanced TS Plug
Tip = High
Sleeve = Shield
Wire Low = Not Connected

12
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
BALANCED
INPUT SUBTRACT BALANCED
OUTPUT
DEPTH
10V REF
REMOTE
CONTROL
RAMP
OUT
EQ VCA
DC CONTROL
EQ
VCA BANDPASS FILTER
LEVEL
VCA
LEVEL VCA
DC CONTROL
Signal Flow Diagram

13
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Troubleshooting
SYMPTOM PROBABLE CAUSE/WHAT TO DO
No output Check cables an connections to see if:
• Inputs are riving outputs, an outputs are riving inputs.
• That there is a signal from the source an that it is getting to the 308.
Check if unit is plugge in.
Hum or buzz in output Check input an output connector wiring.
Check for groun loop problem. Inspect relate system equipment groun -
ing to see that all system components are on the same AC groun .
Distortion Check input signal.
Check if line input signal may be too hot.
If using a high setting for your maximum au io level, you may be overloa -
ing the input to your amplifier; lower the au io level.
Check if something else is clipping in the signal chain.
Noise (hiss) Check input signal levels. The 308 is inten e to operate at or near “line”
level (+4 Bu is nominal). Make sure that the signal you are fee ing to the
308 is a line level signal, not mic level.
Check that all systems components are on the same AC groun .
Check gain settings on upstream equipment. The system gain structure
shoul be such that the 308 receives +4 Bu nominal signal.
No LED display Check if unit is plugge in.
Verify that AC outlet works.

14
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Hardware Specifications
Input/Output
Maximum Input Level +20 Bu balance , +20 Bu unbalance
Maximum Output Level +22 Bu balance , +18 Bu unbalance
Input Impe ance >20k ohms balance , >10k ohms unbalance
Output Impe ance 200 ohms balance , 100 ohms unbalance
Input Common Mo e Rejection >40 B
Performance Data
Frequency Response 20 Hz to 20 kHz +0, – 0.5 B
(with no equalization applie )
20 Hz to 20 kHz +0, –1.5 B (at unity gain with max EQ epth)
THD+N <0.025% at unity gain, 0 Bu in/out
Resi ual Output Noise – 95 Bu typical at unity gain
Gain Control 0 B (unity) to – 65 B
Equalization –15 B max @ 1 kHz
Analog Control
Control inputs accept any of (a) 10k linear rheostat to groun
(b) 10k linear potentiometer from +10 reference output to groun
(c) 0 to 10 VDC control voltage
(d) Symetrix RC-3 Remote Control
Gain Unity at +10 VDC an max attenuation at 0 VDC
Ramp Out Buffere uplicate of the Control In voltage
Auxiliary Power Out +24 VDC ±10%, 100 milliamps max continuous loa
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.

15
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Architects and Engineers Specifications
The VCA volume control / lou ness EQ
shall provi e two channels of remote
level a justment an automatic
lou ness EQ compensation for
controlling a stereo signal in one zone
or mono signals in two zones. There
shall be a voltage controlle amplifier
(VCA) in each channel controlle by
either a 0 to 10 VDC ramp signal or
by a 10k ohms linear taper potenti-
ometer or other compatible remote
control, such as the Symetrix RC-3.
Potentiometers may be locate up to
500 feet from the VCA volume
controller. The lou ness EQ will be
flat at full volume an the output gain
will be at unity. At lower volumes, the
lou ness EQ shall automatically
effectively boost the bass an treble
frequencies by lowering the mi range
response. The maximum mi range
attenuation will be –15 B @ 1 kHz.
The VCA volume control / lou ness EQ
shall provi e two balance line-level
au io inputs on Euroblock connectors.
The input impe ance shall be at least
20k ohms balance , 10k ohms
unbalance . The maximum input level
shall be +20 Bu balance , +20 Bu
unbalance . There shall be two
balance line-level au io outputs on
Euroblock connectors. The output
impe ance shall be 400 ohms bal-
ance , 200 ohms unbalance . The
maximum output level shall be +22
Bu balance , +18 Bu unbalance .
Screw river a justable trimpots shall
be provi e for selecting the amount
of lou ness EQ compensation for each
channel. Nine inputs for remote
control connections shall also be
provi e on Euroblock connectors.
These inputs shall consist of: Ramp
Out, Control In, Groun for each
channel; +10 VDC Out; Groun ; +24
VDC Out.
A front panel power in icator shall be
provi e .
The frequency response shall be +0,
–0.5 B, measure between 20 Hz
an 20 kHz. THD+N shall be less than
0.025% measure at unity gain.
Power consumption shall be 12W
maximum.
The unit shall occupy half of the wi th
of one rack space. The physical
imensions 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 / lou ness EQ
shall operate by means of a Symetrix
PS-3 connecte to 115 VAC nominal,
(95–130 VAC), 60 Hz or a Symetrix
PS-3E connecte to 230 VAC nominal,
(165–255 VAC), 50 to 60 Hz.
The VCA volume control / lou ness EQ
shall be a Symetrix mo el 308 VCA
Volume Control / Lou ness EQ.

16
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Following are the terms and limitations of
the Symetrix warranty.
Warranty
Symetrix, Inc. expressly warrants to the
original purchaser (“Buyer”), subject to the
terms an con itions set forth below, that
the Pro uct will be free from efects in
material an workmanship as a result of
normal commercial use for one (1) year
from the ate of purchase.
Symetrix’s warranty obligation is limite to
the repair, replacement, or refun at
Symetrix’s sole iscretion, of the part or
parts of the Pro uct which may thus prove
efective in materials or workmanship
within one year from ate of purchase
un er normal use an which our examina-
tion iscloses to our satisfaction to be thus
efective, provi e that Buyer gives
Symetrix prompt notice of its warranty
claim an satisfactory proof thereof.
Symetrix will make every reasonable effort
to ensure that parts are available to
support the repair of our pro ucts un er
warranty. In the event that a pro uct or
component part thereof becomes obsolete,
unavailable or irreparable, Symetrix
reserves the right to refun a prorate
portion of the purchase price in full
satisfaction of all warranty claims.
In or er to serve you better we request
that the Buyer shall, prior to shipping
Pro uct to Symetrix for warranty service,
contact Symetrix an secure a Return
Authorization Number that shall be
inclu e with the returne Pro uct. This
will facilitate our efforts to keep track of
your Pro uct an process your warranty
repair as quickly as possible. Buyer will
prepay all freight charges to ship the
Pro uct to Symetrix for warranty inspection
an service. This warranty is subject to
Symetrix’s inspection of the Pro uct at its
facilities an , upon Symetrix’s request,
satisfactory proof of purchase ( ate copy
of original retail ealer’s invoice.)
Symetrix reserves the right to effect
repairs to the pro uct with recon itione
components/parts. Pro ucts once repaire
un er warranty will be shippe to Buyer
freight prepai by Symetrix via Unite
Parcel Service (surface) or any similar
shipper, to any location esignate by
Warranty
buyer within the Continental Unite States.
At Buyer’s request an expense Pro uct
will be returne via airfreight. Outsi e the
continental Unite States, repaire or
replace pro ucts will be returne 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 MER-
CHANTABILITY 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 ACCESSO-
RIES 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 pro uct has been esigne
an manufacture for use in professional/
in ustrial systems an is not inten e for
other usage. This warranty only applies to
Buyers using the Pro uct in professional/
in ustrial systems. With respect to others,
inclu ing but not limite to consumers for
personal, family, or househol 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 mo ify the
esign or make a itions to, or improve-
ments to, its pro uct lines without making
similar upgra es to Pro uct purchase by
Buyer. Symetrix oes not authorize any
thir party, inclu ing any ealer or sales
representative, to assume any liability,
effect any repairs or mo ifications to the
Pro uct, or make any a itional warranties
or representation regar ing the Pro uct or
Pro uct information on behalf of Symetrix.
Symetrix’s total liability on any claim,
whether in contract, tort (inclu ing
negligence) or otherwise arising out of,
connecte with, or resulting from the
manufacture, sale, elivery, resale, repair,
replacement or use of Pro uct will not
excee the purchase price of the Pro uct or
any part thereof which gives rise to the
claim. In no event will Symetrix be liable
for any inci ental or consequential
amages inclu ing but not limite to
amage for lost revenue, cost of capital,
claims of customers for service interrup-
tions or failure to supply, an costs an
expenses incurre in connection with labor,
overhea , transportation, installation or
removal of pro ucts or substitute facilities
or supply houses as a result of Pro uct
failure.
This limite warranty gives Buyer certain
rights. Buyer may have a itional rights
un er applicable law.

17
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
Service
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 authori ation (RA) number. The
telephone number is (425) 78-7728 or email: [email protected]
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 oversi ed 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.
Servicing the 308

18
Symetrix 308 VCA Volume Control/Loudness EQ User’s Guide
We, Symetrix, Inc.
6408 216th St. SW, Mountlake Terrace, Washington USA
eclare un er our sole responsibility that the pro uct:
308 VCA Volume Control/Loudness EQ
to which this eclaration relates, is in conformity with the following stan ar :
EN 55103-2
Electromagnetic Compatibility—Pro uct Family Stan ar for Au io, Vi eo, an
Entertainment Lighting Control Apparatus for Professional Use
Part 2: Immunity
PS-3E power supply complies with this co e:
EN 60065
Safety Requirements for Mains Operate Electronic an Relate Apparatus for
Househol an Similar General Use
The technical construction file is maintaine at:
Symetrix, Inc.
6408 216th St. SW
Mountlake Terrace, WA 98037-2303
USA
The authorize representative locate 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
Authorize signature:
Dane Butcher, Presi ent
Declaration of Conformity