heathkit ta 28 fuzz booster

[LucifersTrip]

Does anyone have any idea why it will cut out with a 0.1uf cap on the input?

Mine doesn't cut out, but it does sag when that 50K up front is jacked. That was my only complaint when I first built it, so I wound up putting a switch between the original and .033, which is the smallest cap I liked before the tone changed too much.

The explanation was given by PRR:

http://www.diystompboxes.com/smfforum/index.php?topic=90489.msg769424#msg769424
"I suspect it would handle chords better (not great) if C1 0.1uFd were much smaller, even 0.01uFd. This with the treble-loading would bandpass a narrow slice of guitar spectrum, so the wide spread of partials on guitar chords did not intermodulate all over the audio band."

...and you're in that thread, too

[Electron Tornado]

Thanks for that link! I recall the discussion going over more than one thread, but when I searched, that one didn't come up. I still don't understand why it happens, though.

[LucifersTrip]

Thanks for that link! I recall the discussion going over more than one thread, but when I searched, that one didn't come up. I still don't understand why it happens, though.

I think you can get the answer by reversing the above, but I'm not good enough to explain it.

.1uF is not bandpassing a narrow slice of guitar spectrum, so the wide spread of partials on guitar chords will intermodulate all over the audio band

[Electron Tornado]

I'm still not sure if that explains what's going on. It depends on what Paul meant by "handle chords". I took that to mean in the same way that a fuzz can sound bad when playing chords due to intermodulation distortion. The problem I'm having is that the signal will actually cut out briefly. Somehow the trons stop flowing for a millisecond.

Hmmm, come to think of it, I wonder if this is somehow an impedance issue, since impedance is frequency dependent.

[PRR]

You are just playing too hard. The simple transistor circuit will rectify large signals and de-bias itself.

[Electron Tornado]

You are just playing too hard. The simple transistor circuit will rectify large signals and de-bias itself.

I don't think I'm playing particularly hard. I can turn the drive control down quite a bit and still have it cut out. The fact that the pedal is OK with an input cap of 0.01uf and cuts out with a 0.1uf cap sounds like a frequency dependent issue. Still a bit of a mystery to me.