Red Llama Volume-Dependent Oscillations

[Ripthorn]

Hey all, new here, but I have read all the threads I could find on the Red Llama and oscillation issues.  I built according to the general guitar gadgets schematic and used 47 pF cap instead of the 51 pF (I figured most 51 pF have a 20% tolerance anyway, so figured I would be fine).  I have checked that all the unused inverter inputs are connected to ground and I don't think I have any stray solder threads (trying to keep an open mind, thus the "I don't think . . "). 

The interesting thing is I get oscillations that vary in pitch when the gain knob is changed, more gain=higher pitch and disappears at roughly 60%.  The weird thing is that if I boost the volume, the problem ceases.  The thing is that then the volume is too much louder than the input signal, so going from clean to effect creates a large jump in loudness.  I was wondering what ideas anyone might have.  Should I try to just knock down the signal before going to the output?  The actual cause of the oscillations puzzles me and I would like to just fix the root cause, but all of the past threads that talk about this don't list any kind of a resolution so I thought if I could at least achieve a suitable workaround then I would be okay with that.  Thanks.

[oskar]

The one you used...
http://www.generalguitargadgets.com/pdf/ggg_whrl_sc.pdf
Another schemo...
http://gaussmarkov.net/layouts/redllama/redllama-schem.png

I don't know if the oscillations is caused by this but if you observe C2 they are hooked up
differently in the two drawings. I would go with the second one...

[John Lyons]

It's possible that the oscillation is caused by your wiring or layout.
Make sure that the output wiring is physically distanced from the input.
This includes wires to the in/out jacks , switch wiring and physical layout of the board.

Got pics?

john

[Ripthorn]

I don't have pictures right now, but I will try to get some.  This was my first project and made it from parts at the local place.  That being said, some of the caps are huge (physically, and not like that has anything to do with it).  The input and output wires on opposite ends of the board, though they may come in close proximity of each other (they are jacketed, though).  I will check and get some pics.

[Ripthorn]

After further messing around with this, I've come to the conclusion that maybe this thing just needs some sort of pad function built into it.  I say this because I can run up to 60% gain without oscillations while the volume is at a usable level.  The only thing: the volume knob is at maybe 10%.  By the time the volume knob is up to 40% or so, my ears almost bleed.  I would like to use the full range of the volume knob and I also think that would also make it so that these issues I face won't be a factor in every day usage.  Would I be better off reducing signal level before or after the 4049?  Any good ideas or schematics for a simple pad?  I am thinking doing something like a voltage divider just before the output jack, but then I am worried about loading.  Any suggestions?

[John Lyons]

What type of pots did you use?
Linear or Log?

The volume should be a log taper.
This will fix your volume problem I believe.
(assuming you used linear)
The oscillation problem has to do with proximity so
the fact that they are insulated doesn't matter.

john