Sustain noise on Big Muff

[MrEvilTooth]

Greetings everyone.

I've just built a Big Muff which looks like this:
http://postimg.org/image/jm0zekqhx/

It works well except for hideous noise which occurs while I'm not playing when Sustain pot is at max, or at any level higher than zero for that matter. I've tried a noise gate mod, checked every connection (it's still on breadboard) and just can't lower or remove it. I've also read that it's normal for Big Muffs to be noisy while not playing, but my noise level is comparable to sound level while I am playing. Unfortunately, I don't have a multimeter yet so I can't post voltages. Any help or suggestion is most welcome.

Thank you in advance, Marko.

[tommycataus]

It may help you to use shielded wire at the input and output, and perhaps even on the sustain pot too. Either that or your wiring might need some re-arrangement so that your input wires are further from your output wires.

You can expect plenty of noise on any high gain pedal if you don't follow these rules. There are some good sources for shielded cable on ebay, it's just like the coaxial cable used for TV cables and the like. All you have to do is use it as described above, and for the braided shielding, just connect one end to ground and leave the other unconnected.

Hopefully this helps

[tommycataus]

Here you go:

http://diy-fever.com/misc/circuit-layout-guidelines/

If you scroll down to "Lead Dress" and "Shielded Wire" this might make more sense than my strange explanation.

[anotherjim]

You could also try grounding some unused breadboard contact strips between stages to act as guard screens. I prefer preset type pots on breadboard to avoid long wires to real pots.

It's a peculiarity of Big Muff circuits that there is no power supply filtering shown. Anything else would have a resistor/cap combination feeding power to the first stage to stop noise fed back via the supply getting amplified by the first stage. I put this in my own build purely out of habit without noticing it isn't on the schematic!

Jim

[nocentelli]

+1 on the power filtering, I have a large cap across the rails on my breadboard which just stays there. I would also advise triple checking you have made every connection exactly as shown on the schematic before you start looking at shielding the input+output. My breadboard isn't shielded, and I don't recall any BMP I've layed out producing a noise floor as high as you describe - the BC caps remove a fair amount of the high sizzle noise and so you're left more of him, but nothing like as loud as the guitar. It sounds like it could be a wrong value or maybe something as simple as a cold solder joint on the volume pot ground.

[Tony Forestiere]

PNP transistors? Positive ground?

[LucifersTrip]

Honestly, I don't really think it's worth screwing with much until you get a multimeter. It's kinda wasting time if the voltages are off....unless you want to double-check you have all component values correct.

There's no BMP I've heard that's as noisy as you described...

...and it should get quieter after soldered and in a metal box

[MrEvilTooth]

Thanks everybody for suggestions, sorry for not replying sooner, been working 12 hr shifts.

I'll try those things today and tell you how it went.