Silonex Compressor Write Up

[raulduke]

Interesting info on the Silonex NSL-32 here.

Including a detailed schematic with ratio, attack, release controls (+ gain reduction meter).

Basically a schematic for a full 'studio' compressor.

http://www.silonex.com/audiohm/compressor.html

I thought our resident compressor guru (midway) might be interested  !

[midwayfair]

Thanks for the link. I saw it at some point but didn't really take a very close look.

The method is similar to what's used in the Diamond, where the optocoupler serves as one leg of a voltage divider.

Both of these examples need an input buffer (if not amplifier) to work well with a guitar, otherwise there will be a lot of input loading. There are also some notable tone changes that come about when using the voltage divider method. One is that high frequencies are attenuated more severely than in a variable gain circuit (like the Afterlife), same as turning down a volume control. The benefit is that it's usually a little quieter as long as the actual amplifier is quiet, because it kills line noise pretty effectively (but the signal:noise ratio is still a concern, because after all at idle it's like havign a volume control at half way).

One thing to remember here, despite having all five controls, is that optical compressors are always limited by the performance of the device in a way that FETs aren't.

The Circuit Salad optofet compressor (there's a thread here) is similar in design (one leg of a voltage divider) but uses a much faster optocoupler and has a wider range of controls (especially shorter attack/turn-on time) available.