Manual

LYDKRAFT ApS
Mose Allé 20, DK 2610 Rødovre
Denmark
1
TUBE-TECH CM 1A
Compressor Module
DESCRIPTION.
The TUBE-TECH compressor CM 1A is based on an opto-coupler as the gain-reduction
element. This non-semiconductor element has a very low harmonic distortion and none of
the non-linearity problems involved when using most semiconductor elements. Furthermore
there is no long-term degradation of the element thus giving it almost infinite life. This
element is placed after the input-transformer and followed by an all tube-based amplifier with
a gain of - dB to +30 dB.
Thus the signal is not fed through any semiconductor circuitry on its way to the output.
The amplifier consists of two dual triodes in push-pull configuration (one ECC 83 as the
pre-amp and phase splitter, and one ECC 82 as the output stage), and an output
transformer.
Both input and output are balanced (600) and fully floating.
The in/out key switches the compressor in and out without clicks.
The amplifier remains in the signal path.
THE SIDECHAIN:
The side chain is the only part of the compressor that contains semiconductors. They are
used for three reasons: First they do not affect the sound reproduction, second they have a
high slew rate, which is of importance for the performance of the compressor and third they
don't take up much room.
It contains two J-FET quad op-amps, one npn-transistor and one FET-transistor, which
handles the signal for the gain-reduction element.
The compressor contains two time constants circuits:
1. Fixed attack and release times
2. Variable attack and release times
The attack/release select switch makes it possible to use these two circuits separately or
combine their functions.
This gives a feature not normally obtained in other compressors:
In the combined (fix. /man.) state, the attack- and release controls makes it possible to
obtain a complex release-time slope. (See page 4)
(080330 JGP)