I'm trying to understand the gyraf audio SSL G series bus compressor kit. I'm having problems wrapping my head around the ratio switching - what exactly is going on with switching in different currents into that full-wave rectifier configuration? How does this and feeding back the signal into the control pin of the sidechain VCA result in accurate ratio control? Everything else seems simple, but on those points I am confused.. schematic link below for your pleasure

http://www.gyraf.dk/gy_pd/ssl/ssl_sch.gif

 

I'm trying to understand the gyraf audio SSL G series bus compressor kit. I'm having problems wrapping my head around the ratio switching - what exactly is going on with switching in different currents into that full-wave rectifier configuration? How does this and feeding back the signal into the control pin of the sidechain VCA result in accurate ratio control? Everything else seems simple, but on those points I am confused.. schematic link below for your pleasure

http://www.gyraf.dk/gy_pd/ssl/ssl_sch.gif

Sounds like the old way of doing things.

If you load the DC terminals of a bridge rectifier; it draws more current in the AC terminals. This fact is transposed into turning a symmetric current source into an assymetric current regulator.

It tends to be more common in video amplifiers contrast control for the old CRT displays.

Most of the variable gain amplifier chips are gone - if you've got too much time on your hands, you can get a DC volume control audio power amplifier to do the job. They tend to be BTL - some will work single ended, some wont.

 

Sounds like the old way of doing things.

If you load the DC terminals of a bridge rectifier; it draws more current in the AC terminals. This fact is transposed into turning a symmetric current source into an assymetric current regulator.

It tends to be more common in video amplifiers contrast control for the old CRT displays.

Most of the variable gain amplifier chips are gone - if you've got too much time on your hands, you can get a DC volume control audio power amplifier to do the job. They tend to be BTL - some will work single ended, some wont.

thanks for the reply, but im not sure we are on the same page - im talking about the precision op amp rectifier circuit in the schematic above, im not sure the current source design you mention is the same thing

I'm fixing one of these kits for a friend, the guy who made it sadly passed away before having time to get it working perfectly. Hence i don't need to find an amplifier chip, but THAT and Coolaudio both make VCAs