Flatline compressor questions

[mlabbee]

Well, I seem to have gotten it working. I got some of those Silones optocouplers and it is definitely having an effect on the signal.  One thing that is kind of odd is that at the top end of the sustain pot, the sound come out for about a second (fairly distorted) and then suddenly drops off completely. Anthoughts on why this might be happening?

Also, I put a bare LED in the place of the optocoupler just to see how it behaves - it lights up, but I see no variation in the intensity . . . shouldn't it be changing intensity with the signal?

Finally, has anyone played around with the Silonex optocouplers much?  They're kind of expensive and I want to avoid trashing them - do they plug into most of the published circuits without modification or should I worry about trashing the LED with too much current?

[toneman]

i would think the LED *would* go out with no signal.
the signal is recified & filtered and the DC used 2 drive the LED.
sounds like the 2nd OA is on all the time.
check for a wiring error.
T

[David]

Without the LDR, you won't have any compression action because the gain on the first op-amp will be fixed.  When I experimented with mine, I learned the hard way to test it in a darkened room until I enclosed the LED and LDR.  What I found was the LED was lit for most of the time the signal was "sustained", flickered a little as it decayed, and finally went out.

I had some weird stuff happen when I breadboarded it too.  Carefully check the connections in the feedback loop around the first op-amp.

[Johan]

the LDR attack and decay time can be very different between different LDR/LED combos
I dont know the one you're using but I have had best results with VTL5c2 of all the comersial ones I tried.

Johan