Ultrasonic oscillation or ????

[guitarkill]

I've built a (working) GGG OS clone for a friend using a RTS PCB and it has way too much noise/hiss, kind of like that RF freq "angry hiss". I've checked everything several times, reflowed all the solder joints, etc. and yet this problem persists. Makes me suspect it's something else, like the PCB layout or something. I did a (quick) search here and have not found anyone else with this problem recently.

Is it possible to have ultrasonic oscillation such a low amount of gain in an opamp circuit?  

And if so, how do I get rid of it?  

Edit: Opamp I am using is a JRC4580, but the actual opamp used does not seem to help at all with the noise.

[PRR]

Does the hiss change when you poke your finger near  the circuit?

[thelonious]

Mark Hammer had a bunch of good suggestions in this post (and there are some other good in the same thread): http://www.diystompboxes.com/smfforum/index.php?topic=59023.msg461327#msg461327 - but if it's really obnoxious hiss there might be something else wrong, as you said, and not just the OS circuit being hissy. Have you tried it on battery? That's an easy way eliminate it being power filtering related. If there's no battery snap just use alligator clips.

[guitarkill]

Does the hiss change when you poke your finger near  the circuit?

No. I guess you were thinking if it was RF that my hand being in close proximity to the circuit would mess with the frequency some and give us a clue, right? Since there was no change I suspected that it's some other problem. My guess right now is the main problem is that the diode has the wrong forward voltage, too low I guess. I will check on that later as I have tried everything else and nothing works.  

Mark Hammer had a bunch of good suggestions in this post (and there are some other good in the same thread): http://www.diystompboxes.com/smfforum/index.php?topic=59023.msg461327#msg461327 - but if it's really obnoxious hiss there might be something else wrong, as you said, and not just the OS circuit being hissy. Have you tried it on battery? That's an easy way eliminate it being power filtering related. If there's no battery snap just use alligator clips.

I have not seen that thread until now but I've already tried most of those things. But there is a couple of things in there I hadn't thought of.

[guitarkill]

OK, well I can't believe what I had to do to do get rid of the hiss while not killing the overall tone:

1. 100pF cap to ground at input
2. 100pF cap in feedback loop of opamp
3. 100uF cap across power supply
4. Changed .047uF caps in signal path to 0.1uF
5. 1N34 diode instead of 1N270
6. .022 cap to ground on output

All that to get the hiss down to about what it is in my OS that I built about ten years ago with different GGG PCB layout I etched myself. WTH is up with that? I'm a little mystified by this.