Dr Boogie oscilates when turned off

[audioguy]

I boxed up my Dr Boogie this eve and when I switch it into by pass it squeels... and it goes up or down depending on how I adjust the tone knobs.

Any possibilities? I've made my leads as short as possible, but I still get it. My wire is not shielded. I now that could be a possibility, but how likely is it?
I can eliminate the squeel by dialing back on the trim pots, but then it doesnt sound as good.

Any suggestions?

thanks!

Audioguy

[Processaurus]

If your bypass scheme leaves the effects input floating, the effect can feedback on itself if its high gain, and has a high impedance input stage.  If the input gets grounded when the effect is bypassed, the feedback will stop, because the input is tied to a low impedance (ground is the lowest impedance), and any stray crosstalk from the ouput gets shunted off to ground.

heres one way of doing it:
http://www.generalguitargadgets.com/diagrams/switch_lo_3pdt_ig_dcjack.gif

[audioguy]

I'll give the switch wiring a shot tomorrow. I am using a 3pdt but its not wired this way... its got the power going into the switch, then to the LED. EDIT- Im using this http://www.diystompboxes.com/beginner/circswled.jpg for my switch wiring

Could it be due to the fact that pretty much every wire in some way crosses over or runs very close to the trim pots?
Tomorrow I'll rewire it and flip it around in the enclosure so that the trim pots are at the opposite side of the rest of the pots. This will keep the majority of the wiring away from the trim pots...
What are your thoughts?

 

[mydementia]

I've built this circuit successfully twice now and haven't had a problem using the GGG 3PDT wiring approach.  Give it a try...should solve your problem.
Regarding crossing wires: I do all my wiring on the bench, then run them where I can in the enclosure - never had a problem yet...but I'm only dealing with DC effects.  The one wire pair I did run as short as possible was the pulsing LED on my EA Trem (since it pulses when the circuit is off).

Good luck!  Dr Boogey is an awesome emu!
Mike

[audioguy]

I love this thing... I just need it to be quiet when I bypass it. I'll rewire my switch later this afternoon and post my results.

Thanks!

[LyleCaldwell]

Always better to switch ground to LEDs rather than to switch the positive supply.  Aside from lowering the voltage at the switch it gives you a ground on the switch to route to effect inputs when bypassed.

[Paul Marossy]

I used a grounded circuit input true bypass on my Dr. Boogie. I did it without even thinking about it twice since I have had that oscillation when in bypass mode problem before... 

[audioguy]

I used a grounded circuit input true bypass on my Dr. Boogie. I did it without even thinking about it twice since I have had that oscillation when in bypass mode problem before... 

So you've had this problem with other units and grounding the TBP switch cured it?

[Paul Marossy]

So you've had this problem with other units and grounding the TBP switch cured it?

Yep.

[audioguy]

COOL... Ive got a fuzz sitting in the corner unused because it does the same thing... but I didnt like it enough to really dive into a solution.

Thanks again!

[Paul Marossy]

Yeah, I did that first on my second (successful) Shaka Tube build. It had this whine when in bypass mode and that fixed it. Been "a believer" ever since. 

[audioguy]

That did it! Sounds A-freakin-mazing!

thanks for all the help gents!

[Paul Marossy]

Glad to hear it.