My Dr Boogie oscillates (whistles) at mid to high gain settings like crazy

[mojotron]

My Dr Boogie sounds awesome, but oscillates (whistles) at mid to high gain settings like crazy as soon as the singal from the guitar drops in amplitude - anyone else have this problem with theirs?

For reference:
Schematic: http://geocities.com/electrictabs/dr.boogey.png
PCB: http://www.4thlevelmedia.com/DrBoogeyPCB.bmp
Parts Layout: http://www.4thlevelmedia.com/DrBoogeyPartsLayout.gif

I have been messing with this circuit on and off for about a month now and I can't figure this one out. I do get an awesome high-gain sound, but the oscillation is annoying and the 'gain', treble and presence control will affect the frequency of the oscillation. With the gain set to mid, treble set around mid and presence set to low, the oscillation disappears, but comes right back if you increase any of those. Any clues as to what to check?

This is what I have tried so far:
If I leave the first stage source by-pass cap (1uF) off the oscillation is a lot less, except for high gain settings.

If I adjust the 3rd trimmer from the left (the one with a 1nF bypass) I can adjust the frequency up to the point where I can't hear it (of course that leaves me with dogs howling all over my neighborhood..  ), but then the sound is weak.

I had this problem with the stock-original circuit, none of this has really helped:
Biased, and rebiased all of the fets.
I checked the 100uF, 1nF and 5nF caps.
I increased the 5nF and 1nF caps, and replaced the 100uF cap.
I checked ground everywhere.

Then, I added 150pF caps from the gate to the source on all of the fets and I have a 270pF cap subbed in for the 20pF cap - this helped just a little. The circuit is enclosed in 2 raco boxes, connected to house all of the controls (there's a bunch) - so the wires are a little long, but not all that long... Also, I am using J201 fets in all positions except for the 1st stage, where I'm using an MPF102 - and that helped a little too.

I'm guessing that either someone else has had this issue, or that the circuit is too new to really have a lot of collective experience on this circuit and I might get a lot of help on this... but after doing some searching and not finding info on an issue with the Dr Boogie, I thought I would ask around.

Any ideas?

[RDV]

The wires to the seperate controls cannot cross each other, and must be short and neat. Mine whistled till I made these things happen. It meant I had to have a funny order to the controls, but it's nice and quiet. I twisted together the 3 wires to each pot and then arranged everything where the bundles would not cross each other, till you can do this, it will whistle.

RDV

[John Lyons]

Welcome to high gain country!
As with building amps, the layout of the wires and controls is crucial.
I would add using shielded with to the input and output leads to the jacks. You may get it to behave without doing this but it will help either way. Sometime it will oscilate at a very high frequency without you knowing it as oscilation... Fun Fun Fun!

John

[mojotron]

The wires to the seperate controls cannot cross each other, and must be short and neat. Mine whistled till I made these things happen. It meant I had to have a funny order to the controls, but it's nice and quiet. I twisted together the 3 wires to each pot and then arranged everything where the bundles would not cross each other, till you can do this, it will whistle.

RDV

Ahh... ya know - that could just be it. I have no order to the wires at all, they are crossing all over the place in side the enclosure - and I noticed a couple of times that if I turn the whole thing upside down (with the board hanging out) the oscillation did change while I tweaked the trimmer pots - which I thought was kind of strange. I would love it that was it - that would explain a lot.

I will check that out tonight - Thanks Ricky!

[mojotron]

Welcome to high gain country!

Ya, I don't think I have ever built anything with this much gain spread out across 4-5 stages like this in a distortion pedal. I've been working on a Plexi pedal project and did not have any issues like this - which is similar in design - but still at least an order of magnitude lower that the Dr Boogie. 

As with building amps, the layout of the wires and controls is crucial.
I would add using shielded with to the input and output leads to the jacks. You may get it to behave without doing this but it will help either way. Sometime it will oscillate at a very high frequency without you knowing it as oscillation... Fun Fun Fun!

John

Yep, I need to start paying attention to this with these kinds of pedals with that many off board controls - Thanks John!

[Bucksears]

Yeah, it's real finicky when it comes to, well, everything inside it. I'm trying to find the time (eventually) to alter the PCB so the parts are farther apart from one another in an effort to reduce noise. Mine is noisy even with humbuckers.

- Buck

[mojotron]

Well - I checked out moving/reorganizing the wires so that they are not touching, rewired the switch and it still has some issues - although I can hear that it did make a difference.

I think this is the right direction to go, I'll have to really minimize the wire lengths and keep working on it. Another difference is that I changed the PCB a bit before I built it - moving parts away from eachother and adding pads on each set of fet pads for the miller caps going from G-S on each fet as has been talked about in prior threads.

I also added the parts that a missing from the DR preamp schematic - this may be a source of oscillation as well.

No doubt, it sounds awesome - it sounds very big, very mean; not like a pedal at all.

I will keep working on this, next I'll reduce the wire length and see if that helps.

Thanks everyone for your help with this!

[$uperpuma]

using shielded wire from the input to the switch and the switch to the board input may help, that was a tip that Mark at OLC gave me and it seems to have helped with noise