Noisy Ol' Wah!

[waspclothes]

Hey guys,
I just got an old Italian "Mister Cry Baby" (it's a wah when on, and a volume pedal when off.. very cool!).

Unfortunately the old pot was completely shot, so I replaced it with a 100K Dunlop Hot Potz. It's working great, but there's background white noise that gets affected by the wah when it's engaged. This is my first old wah, so I'm not sure if that's just par for the course or not?

As you guys know, there ain't much to these circuits. I don't plan on shotgun replacing all the old resistors and capacitors.. if that's the noise an old wah makes, I can live with it. Thoughts?

[Mark Hammer]

Do you have any sense of what sort of volume drop the entire pedal provides? There doesn't appear to be any sort of overall bypass.

[waspclothes]

Do you have any sense of what sort of volume drop the entire pedal provides? There doesn't appear to be any sort of overall bypass.

Hi Mark, I will measure this and report back. I was going to true-bypass it and forget about the volume pedal section.. but my instinct was that there'd be a volume drop.

[waspclothes]

Do you have any sense of what sort of volume drop the entire pedal provides? There doesn't appear to be any sort of overall bypass.

Okay, seems like the pedal actually provides a boost.

With an input of 377 mVRMS @ 1000 Hz, the volume pedal mode goes from 98 to 573 mVRMS.

[Mark Hammer]

So here's the schematic:

I'm not seeing anything that looks inherently hissy. Assuming this is the schematic of your unit, BC183s don't have any sort of reputation for being hissy. All I might suggest is replacing the 10nf and 68k input components with something a little better, like a 1% metal oxide for the 68k and perhaps a polyester for the 10nf.

[Enzo]

But I am not aware of any semiconductors that cannot become hissy. Consider it a failure mode. Hiss generally comes from semiconductors.

[Mark Hammer]

In retrospect, now that I think of it, I bought myself a late 60's Heathkit TA-16 amp a few years ago that was quite hissy. The 2N3391 transistors it used have no reputation as noisy but I stumbled onto some recommendation to change them as a hiss-cure. I did, and by gum it worked. So, maybe one or both of those BC183s deserves to be put out to pasture. Here I would defer to Sensei Enzo's experience and wisdom.