Low End Hum

yclepticon · September 07, 2011, 03:53:20 AM

Hi There,

This is my first post - So, bare with me. I've designed my own fuzz pedal that is sounding pretty fantastic, IMHO, except for a low end hum accompanied with a slight tremolo-ish effect when I'm not playing. It's making a "whomp-whomp-whomp" noise. It isn't very loud and not a big issue, but I'd like to get rid of it if possible. Also, when I turn my guitars volume all the way down I get some slight static - this only happens when it's on 0, if I add a little volume it goes away. I suspect that there is a grounding issue...

Any help would be greatly appreciated. I've searched through the old posts and couldn't find anything that matched this problem.

Thanks for your time!

LucifersTrip · September 07, 2011, 05:37:06 AM

Quote from: yclepticon on September 07, 2011, 03:53:20 AM
Hi There,

This is my first post - So, bare with me. I've designed my own fuzz pedal that is sounding pretty fantastic, IMHO, except for a low end hum accompanied with a slight tremolo-ish effect when I'm not playing. It's making a "whomp-whomp-whomp" noise. It isn't very loud and not a big issue, but I'd like to get rid of it if possible. Also, when I turn my guitars volume all the way down I get some slight static - this only happens when it's on 0, if I add a little volume it goes away. I suspect that there is a grounding issue...

Any help would be greatly appreciated. I've searched through the old posts and couldn't find anything that matched this problem.

Thanks for your time!

you may not want to post the schematic or a closeup pic of the build, but without that, it will be difficult for anyone to give you an educated answer...only guesses, like: "check all your grounding connections"

aron · September 07, 2011, 03:36:13 PM

> except for a low end hum accompanied with a slight tremolo-ish effect when I'm not playing

If I had to guess.... oscillation with the circuit. Too much gain and the wires are maybe routed too close. Try shielded wires for the input and output.

yclepticon · September 07, 2011, 11:59:27 PM

Thanks for the response! I'll keep plugin' away at it.

ACS · September 08, 2011, 12:05:44 AM

Could be the classic 50/60 cycle hum from PS. Does it still do it on battery?

yclepticon · September 08, 2011, 01:21:01 PM

Yeah, it still happens when I run the circuit off a fresh battery.

yclepticon · September 08, 2011, 03:34:40 PM

has anyone encountered static/buzz when your guitar's volume is on zero/ground?

Paul Marossy · September 08, 2011, 06:35:45 PM

Did you confirm that your grounding is good? Are ALL grounds connected together?

yclepticon · September 08, 2011, 11:23:16 PM

yes, all grounds are connected together.

runmikeyrun · September 08, 2011, 11:53:40 PM

sounds like motorboating, like when an old tube amp needs a cap job. idk if that priniciple applies to 9v SS circuits or not though. Is there a cap across + and - ?

yclepticon · September 09, 2011, 01:15:45 AM

yeah, that's a good way to describe it! Or, it sounds like an old hot rod while it's idling - hub-ada-hub-ada-hub-ada.

There are no caps across + & - exclusively. Thanks for all the responses. I know it's hard when I can't/won't post the schematics.

yclepticon · September 09, 2011, 11:05:40 AM

I'm going to start another thread regarding the buzz/static that I'm getting when the guitar's volume is on zero as I probably should have put that in the subject line.

Paul Marossy · September 09, 2011, 04:37:08 PM

Quote from: yclepticon on September 09, 2011, 11:05:40 AM
I'm going to start another thread regarding the buzz/static that I'm getting when the guitar's volume is on zero as I probably should have put that in the subject line.

It's circuit noise. It won't matter if your guitar volume is down or not, it will still make the noise. It's probably something inherent in the design that needs to be identified and fixed.

So your grounding is OK. My next guess is that it is amplifying 60Hz or 120Hz noise and that it is also ocsillating at a very low frequency for some reason. Maybe some better filtering on the power supply might help with the motorboating sound. I find that a 100uF cap across the power supply is usually sufficient.

yclepticon · September 09, 2011, 07:01:49 PM

Actually, the circuit noise was changed when the volume was on zero. It went from "motor boating" to a louder static just from moving the volume between 1 and 0.

From the other thread I believe I mostly found my answer. I've added a 1K resistor before the input cap. It did reduce the tone of the fuzz a bit (it didn't have as much bit), but it both the noise of the pedal and static that I was getting to tolerable levels. Thanks for all your help. It's much appreciated!

Paul Marossy · September 09, 2011, 08:20:00 PM

Quote from: yclepticon on September 09, 2011, 07:01:49 PM
Actually, the circuit noise was changed when the volume was on zero. It went from "motor boating" to a louder static just from moving the volume between 1 and 0.

From the other thread I believe I mostly found my answer. I've added a 1K resistor before the input cap. It did reduce the tone of the fuzz a bit (it didn't have as much bit), but it both the noise of the pedal and static that I was getting to tolerable levels. Thanks for all your help. It's much appreciated!

I didn't see the other thread. So the lack of an input resistor was the culprit, huh? Interesting. Got to remember that for future reference!

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Low End Hum