Author Topic: BSIAB II: footswitching between gain controls - have question  (Read 2242 times)

Bucksears

BSIAB II: footswitching between gain controls - have question
« on: September 29, 2007, 09:37:11 AM »
I put my new BSIAB II into a larger case so I can have a couple of extra footswitches for toggling/gain options.
Referencing the pic below, I have the wires for the gain pot (lugs 3 & 2) going to the center lugs of a DPDT switch. In one direction, they connect to lugs 3 & 2 of an internal, fixed (maxed out) 500k pot; this bypasses Gain1 and 2 for when I just want to hit full gain. In the other direction of the DPDT switch, it connects to the center lugs (on two of the three rows) of a 3PDT switch. The 3PDT switch toggles between two external 500k gain pots; they're independent of each other, so I can set them for two different (lower) gain settings. The third row of lugs on the 3PDT switch has an LED (not shown in the pic) for Gain2 mode.



Everything functions just fine, but....
I'm wondering about how the switches should be grounded. I have the on/off footswitch wired for a grounded input, but I'm getting just a WEE bit of hum. It goes away when I touch the case or one of the footswitches. It's still there, so I can't say that it's dead quiet, but very close. My GGG Big Muff doesn't have this hum, so it's something in the pedal.
I hate to be a stickler about such a small amount of noise, but since it goes away when I touch the switch, it has to be a grounding issue.
Any ideas?

Thanks,
- Buck

Auke Haarsma

Re: BSIAB II: footswitching between gain controls - have question
« Reply #1 on: October 01, 2007, 11:05:37 AM »
I'm no expert, but I'd say all pots are grounded, so it's probably not a pot-grounding issue.

(and this is a polite way to bump your topic  :icon_wink:)

Bucksears

Re: BSIAB II: footswitching between gain controls - have question
« Reply #2 on: October 01, 2007, 12:31:36 PM »
Thanks, Pong.
Actually, I'm starting to wonder about the guitar. I didn't notice any buzz/hum before with my GGG Big Muff, but did this weekend; same amount of low hum/buzz that's barely there, but still there, ya know?
It goes away when I touch the footswitch or the control plate on my Tele, so I think the Tele is the culprit. It has DiMarzio noiseless pickups, so I'll check the wiring there.

All in all, it's not a ridiculous amount of noise (very low), but I'd still like to be free of it.

Thanks again,
- Buck

John Lyons

Re: BSIAB II: footswitching between gain controls - have question
« Reply #3 on: October 01, 2007, 09:47:23 PM »
The wiring looks right, as long as you use short wire runs the way you are doing it shouldn't increase noise or hum.
TYhe ground wire only shunts some signal to ground depending on where the pot is set (resistive divider).

Does the hum go away with one hand on the strings and by touching the switches on the pedal case?
Or does the hum go away while not touching the guitar while on and then touching the switches?
If the second one is true then it's not the pedal wiring.
The only way I could see to improve the wiring (and only if the wires were over 3 inches or more in length) is to use shielded wiring.

John

Basic Audio Pedals
www.basicaudio.net/

Bucksears

Re: BSIAB II: footswitching between gain controls - have question
« Reply #4 on: October 02, 2007, 11:53:56 AM »
If I'm not touching the strings, the hum dies down if I touch one of the footswitches, OR the control plate on my Tele.
It's gotta be the guitar at this point.
Thanks,

- Buck

cheeb

Re: BSIAB II: footswitching between gain controls - have question
« Reply #5 on: October 02, 2007, 03:47:22 PM »
I hate that. My strat is the world's worst. You can wrap a wire around a finger on your strumming hand and at the other end, attach an alligator clip and clip it to the bridge or something to ground it. You can also check this site out. http://www.guitarnuts.com/technical/electrical/trouble/strat.php