Author Topic: Noisy when pot is turned, quiet otherwise  (Read 7074 times)

sarpedon

Noisy when pot is turned, quiet otherwise
« on: July 25, 2007, 10:56:55 AM »
I built the beginner project and it seems to work well when at a constant level.  However, when turning the pot to change the boost level it has a static-y sort of scraping noise.  Any guesses if this is a problem with the circuit or a bad choice of pot perhaps, http://www.mouser.com/search/refine.aspx?Ntt=313-1210F-5K is what I have in my circuit now.
Builds Completed: Smalley Boost, Blackfire, Uglyface Perf
Builds In Progress: Uglyface PCB, ProCo Rat, Thor, Big Muff Pi

aron

Re: Noisy when pot is turned, quiet otherwise
« Reply #1 on: July 25, 2007, 05:43:07 PM »
I suppose it could be the pot if everything else works.

cheeb

Re: Noisy when pot is turned, quiet otherwise
« Reply #2 on: July 25, 2007, 07:31:22 PM »
I've built four of these and two of them have this problem. I can't figure it out either. Sounds like scratchy pots on wahs, but cleaning them doesn't help.

sarpedon

Re: Noisy when pot is turned, quiet otherwise
« Reply #3 on: July 25, 2007, 07:53:55 PM »
Yup, that's the sound I'm getting.  I replaced mine, with one of the same model, and it seems a bit better possibly but it's still there.  It's on a breadboard now I'll see if it persists when I put it on a perfboard.
Builds Completed: Smalley Boost, Blackfire, Uglyface Perf
Builds In Progress: Uglyface PCB, ProCo Rat, Thor, Big Muff Pi

sarpedon

Re: Noisy when pot is turned, quiet otherwise
« Reply #4 on: July 26, 2007, 12:11:00 AM »
Well the perfboard build worked well, but the scratch-y noise is still there when adjusting.  Maybe I'll try a different type of pot in the future.

My complete noob moment for the build was putting everything in the box, testing it and getting no output at all.  I was pretty discouraged and it was midnight at this point so I took the whole thing out of the box to test tomorrow.  While taking it out I noticed a completely empty transistor socket :P  After fixing that it works just fine.
Builds Completed: Smalley Boost, Blackfire, Uglyface Perf
Builds In Progress: Uglyface PCB, ProCo Rat, Thor, Big Muff Pi

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #5 on: July 26, 2007, 12:16:48 AM »
replace the last cap in the circuit, it could be leaking DC onto the volume pot.

sarpedon

Re: Noisy when pot is turned, quiet otherwise
« Reply #6 on: July 26, 2007, 12:27:39 PM »
Sorry, but which qualifies as the last, the 10uF?

I'm not entirely clear on the workings of the circuit, I'd guess it's the 47uF because that's coming off of the emitter which should be the higher gain output from the transistor.  But the 10uF foes to the output connection, so I'm a bit confused.

If it's the 47uF then I replaced that along with the potentiometer already.
« Last Edit: July 26, 2007, 12:33:06 PM by sarpedon »
Builds Completed: Smalley Boost, Blackfire, Uglyface Perf
Builds In Progress: Uglyface PCB, ProCo Rat, Thor, Big Muff Pi

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #7 on: July 26, 2007, 03:34:20 PM »
I'm referring the the very last before the output, which would be the 10uF

sarpedon

Re: Noisy when pot is turned, quiet otherwise
« Reply #8 on: August 18, 2007, 01:58:48 PM »
Finally got around to replacing the capacitor and building an enclosure.  Still has the scratchy noise when it's turned, but I can live with it.
Builds Completed: Smalley Boost, Blackfire, Uglyface Perf
Builds In Progress: Uglyface PCB, ProCo Rat, Thor, Big Muff Pi

12milluz

Re: Noisy when pot is turned, quiet otherwise
« Reply #9 on: August 19, 2007, 10:20:30 PM »
I have this same issue, non resolved.
Quote from: Processaurus
You need a glade plug-in, in on a footswitch.  Kick on the big muff, then hit the air freshener pedal.

Visit my site: http://www.freewebs.com/12milluzmusic

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #10 on: August 20, 2007, 06:53:44 PM »
check for voltage on any lug of the output volume pot. if you have any, something is leaking voltage to it.

also, overheating a pot can damage it. try just clipping or twisting the leads to a replacement pot, but don't solder. then if it works, you are probably overheating the pots when you solder.

nisios

Re: Noisy when pot is turned, quiet otherwise
« Reply #11 on: September 25, 2007, 08:52:51 AM »
Hey barcode!!!

HAve you even looked at the schematic of the booster?
There is no volume pot !!!!

Is there any other way of getting arround this or is it jyst a fact because of the dc along the gain pot?

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #12 on: September 25, 2007, 09:20:04 PM »
fine, on the lugs of WHATEVER pot you are referring to.

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #13 on: November 17, 2007, 01:27:32 AM »
an update: i just built the project too and got the same result! what is the DEAL?!?!?

johngreene

Re: Noisy when pot is turned, quiet otherwise
« Reply #14 on: November 17, 2007, 01:34:45 PM »
an update: i just built the project too and got the same result! what is the DEAL?!?!?
Some noise isn't surprising. As you turn the pot, the DC on the wiper is changing. Therefore the charge on the cap needs to change. This means a small amount of current flow, therefore noise. The quality of the cap is probably the major factor in how much noise you will get.

--john
I started out with nothing... I still have most of it.

Gus

Re: Noisy when pot is turned, quiet otherwise
« Reply #15 on: November 17, 2007, 02:53:08 PM »
As John posted it might be the cap quality.

If you look close it is the same type gain control that a FF type circuit uses.  The cap AC bypasses the section of the pot from wiper setting to ground.

If I had this problem I would test the cap on a meter that checks leakage at working voltage and DA

Try a 1uf or bigger film at the wiper of the gain pot

Barcode80

Re: Noisy when pot is turned, quiet otherwise
« Reply #16 on: November 17, 2007, 03:14:39 PM »
wiper to where?

johngreene

Re: Noisy when pot is turned, quiet otherwise
« Reply #17 on: November 17, 2007, 03:45:37 PM »
wiper to where?
ground. In place of the 47 uF.
I started out with nothing... I still have most of it.

Re: Noisy when pot is turned, quiet otherwise
« Reply #18 on: January 05, 2008, 10:38:46 PM »
Mr. John is right. Consider the Zvex super hard on. written on the top is "crackle ok", because Although the circuit is different, the fundamental prinicpal is the same. So a little noise when turning the pot is no biggie! I actually just built this for the first time. I'm an audio / electronics geek, but i've always bought my pedals. I've found building is fun! I got all the stuff at Radio Shack! haha! I made my board a tab bit larger so that I could try different mods without being so cramped on the tiny board.