Neve 33609 Technical Handbook

33609/JD Limiter/Compressor

Technical Handbook

527-148

Issue 1

© 2003 AMS Neve plc own the copyright of all
information and drawings contained in this manual which
are not to be copied or reproduced by any means or
disclosed in part or whole to any third party without
written permission.

As part of our policy of continual product improvement,
we reserve the right to alter specifications without notice
but with due regard to all current legislation.

Disclaimer: The information in this manual has been
carefully checked and is believed to be accurate at the
time of publication. However, no responsibility is taken by
us for inaccuracies, errors or omissions nor any liability
assumed for any loss or damage resulting either directly or
indirectly from use of the information contained within it.

HEAD OFFICE

AMS NEVE PLC • BILLINGTON ROAD • BURNLEY

LANCS BB11 5UB • ENGLAND

TELEPHONE: [phone] • FAX: [phone]

LONDON OFFICE

TELEPHONE: [phone] • FAX: [phone]

NORTH AMERICAN OFFICES

AMS NEVE INC., NEW YORK

TEL: [phone] • FAX: [phone]

AMS NEVE INC., HOLLYWOOD

TEL: [phone] • FAX: [phone]

e-mail: [e-mail]

http://www.ams-neve.com

1. Limiter/Compressor Unit

Introduction

The limiter/compressor unit contains two identical, isolated channels which are suitable for mono,
stereo or independent operation; units can be linked for multi-channel use. When limiting and
compression is not required, both channels may be by-passed. Both mono, stereo and by-pass
functions are switched by logic-controlled relays. Depending on the position of an EXTernal –
INTernal switch, these functions are either operated by front panel switches or externally
controlled by a rear panel connector. The above switches are internally illuminated from the Logic
to show the operational mode of the unit, and external tallies are available via the rear panel
connector. The reset position of the relays is BY-PASS and MONO: when power is disconnected
or switched off, the unit is in BY-PASS mode.
The limiter/compressor unit contains the following four identifiable sections:

• Limiter/Compressor board (11475): This is a motherboard which contains the

attenuator control element, the 10340-C amplifier and the limiting and
compression sidechain electronics.

• The external control potentiometers, switches and gain reduction meters (which

indicate the overall gain reduction in each channel during limiting and
compression) are mounted on the front panel.

• Input and output sockets mounted on the rear panel.

• A D.C power and relay logic board, which provides a regulated +24V supply

for the 11475 board, and +5V for logic circuits controlling the relay switching.

Limiter/Compressor Board (11475)

This board contains the main audio signal processing circuits of the limiter/compressor unit. The
operation of the board is described elsewhere.

Front Panel Switches

The rotary control switches located on the front panel of the unit are multi-contact multi-layer
rotary switches. Electrical loading of the switches is provided via resistors connected across the
contacts.

Limiter/Compressor Technical Handbook Page 1

Mains Power Supply

The 24V DC input, derived from the main supply, required by the limiter/compressor board
(11475) is supplied by a power supply unit located in the limiter/compressor unit. The power
supply unit comprises a toroidal mains input transformer (TF14201), a regulator circuit (part of

11720), and associated components. The arrangement is shown as part of the limiter/compressor
block diagram EB20515.

Mains power is applied via an IEC inlet connector to the front panel mounted switch POWER. The
switch illuminates when the unit is switched on. Input voltages of 100V, 120V, 220V or 240V AC
can be selected using the voltage selector mounted on the rear panel. Primary circuit protection is
provided by a 500mA anti-surge fuse for 100V, 120V, 220V or 240V operation, the fuse is located
in the body of the voltage selector.

The 24V AC output of the toroidal transformer is connected to the secondary protection fuse, a
500mA anti-surge type, mounted on the rear panel of the unit.

Specification

Frequency Response 20Hz to 20kHz +/-0.5dB, measured at 0dBu relative to 1kHz.

Noise -75dBu with input terminated in 600 ohms, by-passed IN, compress and

limit OFF;

-55dBu with compress IN and gain make-up at maximum.

Limit Level +4dBu to +15dBu, measured with limit recovery set at 50ms, level at

+8dBu using a 1kHz sine-wave at +20dBu and +8 control adjusted to give
+8dBu output.

Limit Ratio with input level at 10dBu, increased to +20dBu the change in output level

should be 0.1dB, +/-0.1dB.

Attack Time slow: 4ms, +/-1ms

fast: 2ms, +/-1ms
being the time taken for a signal to return to within 1dB of its original
value, using an increase in input level of 10dB on an input adjusted to
+10dBu at 1kHz.

Limit Recovery this is the time taken by the control voltage to reach a new value when

an input at +20dBu is reduced in value by 10dB. The recovery times can
be set to 50ms, 100ms, 200ms, 800ms, AUTO 1 1500ms, AUTO 2
3000ms (all +/-50%).

Gain Make-up settings 0 to 20dB correspond with output level +/-0.5dB.

Limiter/Compressor Technical Handbook Page

2

Compress Ratio recovery set to 100ms

threshold to -20dBu
input 1kHz at 0dBu
for each setting of the Compress Ratio Switch the input level is increased
by 10dB and the change in output level should be:

Compress Ratio

Switch

1.5 : 1 6.5
2 : 1 5.0
3 : 1 3.5
4 : 1 2.5
5 : 1 1.5

O/P Level

Change (dBu)

Tolerance

(dB)

±

1

±

1

±

1

±

0.5

±

0.5

Compress Recovery 100ms, 400ms, 800ms, 1500ms

AUTO 1 800ms AUTO 2 1500ms

Distortion 0.075% maximum (bypass IN, Compress and Limit OUT, input level at

+9dBu, 1KHz).

0.2% maximum (Compress IN ratio 6:1, Gain make-up to MAX, Recovery
800ms, Threshold –18dBu).

0.45% maximum (Limit IN, Compress OUT, Recovery 800ms. Input level
+22dBu, Threshold –18dBu).

Power Consumption 5.3VA

Dimensions Length: 482mm (19in)

Height: 88mm (3.26in)
Depth: 255mm (10.03in)

Limiter/Compressor Technical Handbook Page

3

2. Switch Assembly Information

Assembly information for the following switches is included in this section:

Switch Function

Compress Ratio PL20233
Gain Make-Up PL20234
Compress Threshold PL20235
Compress Recovery PL20236
Limit Recovery PL20237
Limit level PL20238

Limiter/Compressor Technical Handbook Page

4