Many of the compressors on the market are based on the old Ross / Dynacomp design, which were great in their day. They used an LM3080 trans-conductance op amp in the signal path to control the volume, but these LM3080 op amps are quite noisy so at low input level we get maximum gain on the LM3080 and therefore quite a bit of noise out. Also, as the Ross / Dynacomp style of product are feedback compressors, they take a while to recover when going out of “compression” so you end up with a “pumping” effect to the volume.
This is the Mozztronics take on a compressor pedal. Our solution is to use the newer low noise LM13700 instead of the old LM3080, and put it in the feedback path so when output volume is highest, the gain of the LM13700 is lowest, giving the lowest possible output noise. We also used a feed-forward control so going into or out of compression is very smooth & we don’t get the “pumping” effect.
RATIO controls the amount of compression from barely on to flat-line, ATTACK controls the speed at which the compression starts to operate, so as to let through initial dynamics & keep sparkle in the sound (as some compressors tend to suck the life out of the signal), VOLUME adjusts the overall volume out of the pedal. There is also a BRIGHT switch, especially useful for guitar, to add a little “zing”