Lynden Audio Modules

Audio Modules


4079 Equalising Amplifier
4088 Limiter / Compressor

4079 Equalising Amplifier


This board provides 20dB of lift and cut at Bass (150Hz) and Treble (4.5kHz) frequencies. Controls may, if required, be fitted directly on the pcb (Electrospeed sell suitable PCB mount lin controls).
An auxiliary output is provided from the first stage (pre-eq) for by-pass or other purposes.

Stock no. 01-145 4079 Price: 25
Technical Specifications
  Dimensions 25 x 112 x 15 mm
  Supply +/- 12v DC @ 20mA
  Response 25Hz - 20kHz +/- 0.5dB (controls centred)
Bass Mid = 150Hz Treble Mid = 4.5kHz


  4088 Limiter / Compressor

The 4088 is a general purpose compressor card, featuring true RMS signal detection within the control loop and eight selectable compression slopes, from 1.27:1 to 10:1. Another useful feature is that at 6dB of compression the input and output levels remain constant, which means that the compression slope can be changed without the necessity to re-adjust gains. (see fig.)
The compression slope can either be selected by the DIL switch on the card or via a 16 way DIL header and front panel switch.

There is an on-board LED to indicate the onset of compression with provision to connect an external LED if required with no necessity for any change to the 4088 pcb.
The threshold can be set by VR2 on the PCB to allow for input levels of between +10 and -10 dbm, for 6dB of compression. The other pre-set (VR1) is factory set to minimise the VCA distortion.
Another useful addition is a separate VCA control pin, (4b), to enable the 4088 to be used as a VCA card with external control. This require approx. -30mv/dB of attenuation.
Because of the RMS rectifier characteristic of the control loop, independent adjustment of attack and release times is not possible. The capacitor C6 can be changed to accommodate different attack/release times if desired. This is approx. 127dB/sec. The release rate can be calculated for other values of C6 by using the formula 1267/C(uF) dB/sec, where C is the value of C6.

Stock no. 01-150 4088 Price: 75
Technical Specifications
  Dimensions 67 x 114 x 15 mm
  Supply +/- 12v to +/- 15v DC @ 30mA



Lynden Micros Limited
Unit 4 Copse Business Centre
Hounsdown Business Park

SO40 9LR

Tel:(023) 8066 3200
Fax:(023) 8086 4659

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