GSSL Side chain problem

[marcfrom]

Hi guys,
I just built a GSSL with turbo and two Super side chain boards.

Everything working but i have a problem with the internal side chain.

When i unplug the right input the left channel have 3db more gain. i don't have this problem with the right channel, when i unplug the right input the gain stay the same.

I listen the outputs of the Super side chain, even when i unplug the right input, the left SC signal have no gain.

But when i listen the left side chain signal at the 33K resistor around the LF347 (quad) the gain up of 3dB when i unplug the right channel.

Anyone have an idea?

Thanks

 

[Harpo]

Isolate the problem, whether its SCF-boards or turbo/gssl-sc.
Double check for same signal level at both SCF-boards outputs (before the 47K summing resistor on SCF-pcb) and for a seperate signal feed per each SCF-board. You might have a provision for gssl-/turbo-mode switchable and wired the differing SCF-board input resistors (10K/20K) wrong.
Identical parts and parts values on turbo pcb and GSSL sidechain ? (both pcbs fitted with quad opamps LF347 instead of TL074, same type VCAs, 10Ks between VCA-pins 3/5 not fitted, VCA-pin4 connected, ...).