DOD 280 LDR/LED question

[oldrocker]

I read all the past posts on this subject but I wanted to know if this is normal.  When power is on the LED in the shrink tube lights up.  Not to complete brightness but I can see it is on.  Is this normal or should the LED be off until there's a signal at the input?

[Ashurbanipal]

I built a DOD 280 and it compresses even with the compression knob all the way down. So maybe this is normal for that compressor. I used a optocoupler or whatever they're called and it's totally enclosed, so I can't see what's happening in there. I use an OPA2604 IC in there now. The compression is very slight with the knob all the way down to a little more than I'll ever use with it all the way up. I tried an NE5532 and there was lots of compression with the knob down and insane amounts with it up. I don't like heavy compression though and I use it mostly on bass.

[oldrocker]

Does anyone know what is the best color for an LED used with the LDR?  And what resistant values (NO LIGHT \ Full LIGHT Brightness) for the LDR.  I used a clear LED that turns red when lit.

[oldrocker]

I'm still stumped on this 280 build.  Now I got sound but it doesn't even need to have Q1 & Q2 installed to get a sound which just bypasses the signal out of pin 1 on the opamp.  My other question is why is there such a big difference between TonePads schem and the GGG schems.  Usually they are pretty close but there are some major resistant values that are different like TP will use 100k and GGG will have 10k.  These are major dissimularities IMO.  Which site did most of you that built this use.  I used tonepad and I'm thinking now I should've GGG.

[Ashurbanipal]

I built the GGG 280a, the one modified for NSL-32 opto coupler:
http://www.generalguitargadgets.com/pdf/ggg_opcomp280a.pdf

...because I had several NSL-32s laying around. I used 2n5088 for transistors because that's what I had. I started out with the TL072, tried many ICs, and ended up liking the OPA2604 the best. The compression is light with the OPA2604, but that's what I like. Compression was very heavy with NE5532.

I would think you would get a signal with no compression without the transistors since that's the part of the circuit that drives the led/opto coupler.

Do you get no compression with the transistors in? Maybe try higher gain transistors or different ICs to see if any result in more compression. Unfortunately, I don't understand the circuit well enough to suggest anything other than trying things like that. Or maybe try an optocoupler instead of your led/ldr.

[jrc4558]

to "reduce" compression, try lowering the value of R5. better yet, install a potentiometer insteal, 1MA will do, and try to dial in the compression you want. Also, increasing R10 may help. again, use a 5k pot and find the position you want, then unsloder it, measure the resistance and replace with the closest available value fixed resistor.

[oldrocker]

What voltage should I have at the collectors of Q1 and Q2?  I have 7.4V with the 4.7k.  This seems super high to me.  I was wondering what voltages I should have there.  Since the LED (diode) goes from + volts to the 4.7k and then to the trannys collectors is it possible that my LED is passing too much current?