Microhponic sounding noise and a lot of feedback when playing BSIAB2

[davidjnichols]

Shortened all the wires as much as possible and tried to get nothing running parallel, but it's still making the weird feedback when I play.  I'm about to swap out the transistors for lower gain ones.  Hopefully that will help.  Also, there is a ton of noise/hum when the gain is more than half way up.  I assume some of that is just because it's such a high gain pedal. Any suggestions for reducing that noise?

[pappasmurfsharem]

Mine is dead silent at max gain when the strings are muted using all stock values except R8 pulled for more bass.
So its not just the circuit

[armdnrdy]

Shielded wire is your friend.  For audio frequencies, the shield should be grounded at one end only. 

As amptramp stated.

You can shorten the wires but if they are still to close to sensitive areas they will create noise.

It sounds as if there is nothing wrong with this design, (others have built it with no issues) so I think it would be a great idea to shield the input/output jacks to the switch and the board input/outputs to the switch. Use RG-174U. Use the search function "shielding" for instruction.

[davidjnichols]

Shielded wire is your friend.  For audio frequencies, the shield should be grounded at one end only. 

As amptramp stated.

You can shorten the wires but if they are still to close to sensitive areas they will create noise.

It sounds as if there is nothing wrong with this design, (others have built it with no issues) so I think it would be a great idea to shield the input/output jacks to the switch and the board input/outputs to the switch. Use RG-174U. Use the search function "shielding" for instruction.

I shielded the input but I'll go back and do the output right now.  All I have for shielded cable right now is radio shack "audio wire".  It's shielded but has two insulated wires inside mesh shield instead of one.  Should still work fine when I just use one of the two wires, right?

[armdnrdy]

Should still work fine when I just use one of the two wires, right?

Yes.
connect only one end of the shield to ground and do at least the board output to the switch (where the high gain signal is originating from) and from the switch to the output jack as well. (where the high gain signal is going to)

[Paul Marossy]

Shortened all the wires as much as possible and tried to get nothing running parallel, but it's still making the weird feedback when I play.  I'm about to swap out the transistors for lower gain ones.  Hopefully that will help.  Also, there is a ton of noise/hum when the gain is more than half way up.  I assume some of that is just because it's such a high gain pedal. Any suggestions for reducing that noise?

OK...

So you're sure that there are no mistakes anywhere in the circuit? Maybe a wrong value resistor or capacitor somewhere?

As noted, if properly working it shouldn't make much noise. Does it behave this way anywhere you go or have you tried it only in one physical location? Just wondering if environment is maybe a factor somehow.

Also, your enclosure is connected to ground, right?

[armdnrdy]

Also, your enclosure is connected to ground, right?

If you look at the image of his "Satan" pedal, he's using regular input/output jacks....assuming the nuts are properly tightened and the interior isn't painted, the jacks should be "grounding" the enclosure through the sleeve.

[Paul Marossy]

Also, your enclosure is connected to ground, right?

If you look at the image of his "Satan" pedal, he's using regular input/output jacks....assuming the nuts are properly tightened and the interior isn't painted, the jacks should be "grounding" the enclosure through the sleeve.

Well I had to ask since it almost sounds like he has no shielding at all. 

[davidjnichols]

As of now, these are all shielded:

input jack > switch
switch > circuit board
circuit board output (volume pot) > switch
switch > output jack

No difference whatsoever. 

Now I begin the arduous task of rechecking all my components to make sure I didn't use an incorrect value somewhere.

[davidjnichols]

Checked all my components and everything is the proper value.  I also double checked my soldering to make sure there wasn't any accidental solder bridges or anything.  All looked good.  Still feedbacky and noisy.  Hmmm...  I suppose I'll try swapping out some transistors now? 

[davidjnichols]

I just noticed that the hum gets significantly quieter when I switch to the center pickup position on my guitar (Les Paul) rather than just neck or bridge.  I also gave my pickups a little tap with the pick and it came loudly through the amp.  Sounds like microphonic pickups.  However, the guitar doesn't do that with other pedals.  I also plugged in a strat and telecaster and got the same results.  What in the pedal could be causing the pickups to go microphonic?

I opened the back of the pedal while it was plugged in and turned on and tapped on the insides.  Every time I tapped on a wire, it came through the amp as if I were tapping on a microphone.  My pedal has in fact become the home of Satan himself.  But other than the devil, what would cause a pedal to become microphonic?  Bad grounding?  Bad solder joint somewhere?  I've checked and rechecked all that and I'm fresh out of ideas, other than simply a bad component.

[amptramp]

Are you using any high-value ceramic capacitors?  They are known to be microphonic as well as non-linear.

[davidjnichols]

Are you using any high-value ceramic capacitors?  They are known to be microphonic as well as non-linear.

Just the 51pf ceramic caps required per GGG layout. I'm using all box caps for the .022's and .0022's. Would that have an impact?

EDIT: I mean the 150pf and 250pf ceramic caps, not 51pf.

[amptramp]

Are you using any high-value ceramic capacitors?  They are known to be microphonic as well as non-linear.

Just the 51pf ceramic caps required per GGG layout. I'm using all box caps for the .022's and .0022's. Would that have an impact?

EDIT: I mean the 150pf and 250pf ceramic caps, not 51pf.

Probably not for the low value caps.  If you get into larger ceramic caps like .022, some of them use a dielectric that is piezoelectric and acts like a microphone.  Also, is the feedback electric or acoustic?  If you are listening through headphones of with the amp turned down, does it vary with volume?

[Paul Marossy]

If you get into larger ceramic caps like .022, some of them use a dielectric that is piezoelectric and acts like a microphone. 

This to me would be very odd in a 9V pedal as I have amps that have high voltage B+ on large value ceramic caps (.022uF or more) and there are no microphonics whatsoever. But these amps are old, maybe the ceramic caps these days aren't as good as the old ones?

[Paul Marossy]

It's built exactly like GGG.

In my mind, you should have gotten this to work by now with all the things you've tried. So I have to ask: did you build this on a PCB exactly like GGG's layout or did you use some other method? And if on perf or vero, are you positive that you didn't make a wrong connection somewhere?

[davidjnichols]

In my mind, you should have gotten this to work by now with all the things you've tried. So I have to ask: did you build this on a PCB exactly like GGG's layout or did you use some other method? And if on perf or vero, are you positive that you didn't make a wrong connection somewhere?

I know!  It's driving me crazy.  I built it using the PCB layout from the GGG website.  Etched and drilled it myself, but used their PCB graphic.  I checked and re-checked all my solder joints and ran it with a razor blade to make sure there were no small, unwanted solder bridges.  I etched two boards, so I think today I may build the second one, install it in the enclosure, and see if I have different results.  The only thing I can think of is a bad component somewhere.

[Paul Marossy]

In my mind, you should have gotten this to work by now with all the things you've tried. So I have to ask: did you build this on a PCB exactly like GGG's layout or did you use some other method? And if on perf or vero, are you positive that you didn't make a wrong connection somewhere?

I know!  It's driving me crazy.  I built it using the PCB layout from the GGG website.  Etched and drilled it myself, but used their PCB graphic.  I checked and re-checked all my solder joints and ran it with a razor blade to make sure there were no small, unwanted solder bridges.  I etched two boards, so I think today I may build the second one, install it in the enclosure, and see if I have different results.  The only thing I can think of is a bad component somewhere.

Could be a bad solder joint somewhere. I've had solder joints that looked great but were dodgy.

[davidjnichols]

Okay so I rebuilt the thing on the other PCB I etched and it works! Minimal noise even when gain is all the way up! Leads me to believe I either had a bad solder joint somewhere or a bad component. This new version seems to have less gain though. Still gets pretty dirty, but the last one would get massively saturated. Maybe I had a bad transistor causing the excess gain and feedback. Although this new one doesn't get as dirty, I still really enjoy it and it is very usable. Thank you so much for all the help. I greatly appreciate it. I look forward to rockin' my evil BSIAB! Thank you!

[deadastronaut]

cool, glad you got it sorted in the end..

sometimes its just less of a headbang to just knuckle down and build anoher...