BSIAB2 Sensitivity Question

[railhead]

I built a slightly modded version of the BSIAB2, the only changes being the 560pF and 1uF cap (from 470pF and .1uF), I totally LOVE the sound, and I'm still tweaking to taste -- but I have a question about the sensitivity/"spittiness." I should have recorded what I'm talking about, but now I'm at work, so I'll try and explain it as best I can...

Fire everything up like you're a bout to play, and lightly rub your finger on the strings without hardly applying any pressure at all. When I do this, I get a Fuzz Factory-like spitting/zipping sound. The thing's so sensitive, it's picking up up the slightest touch on the strings.

Now, this is no big deal to me at all -- though I can see where it could lead to some extra noisy solos if you aren't careful -- but I was wondering if this is normal for this circuit. I haven't messed with this issue much -- and my extra hot WCR Goodwood pups in my Les Paul could be adding to the sensitivity -- but I thought I'd ask to se if anyone else noticed this.

Does my description make sense at all?

[Bucksears]

Sounds like the trimpot isn't at that 'sweet spot' to me, but I could be wrong.
Also check the orientation of your transistors.

[railhead]

The trannys are good, and I've been setting the trimpot by ear as the voltages GGG recommends add too much background noise on all three of builds I've done. What I'm doing is just turning down the trimmer until I hardly hear any noise/hiss at all.

[snoof]

If the trimpot is set too low, or too high, the tranny won't work correctly, you may be right on the edge of either of those settings.  You should probably measure the voltage on that trimpot where you have it set so you can eliminate that as your prob.  I would bet that that is where the weird noise is coming from...

[John Lyons]

+ 1, I think that's the problem as well. If the noise is going away as you describe, you are most likely on the edge of gating and there isn't enough voltage.

John

[railhead]

Do your builds of this circuit typically have a lot of background hiss? Not to bring up ZVEX peds again, but as soon as I turn on the BoR, I can hear the gain hiss. The BSIAB2 is kind of doing the same thing.

[snoof]

all of my bsiab's are noisy to a certain extent.  I wouldn't say REAL noisy, but there's def some noise that is easily heard.  It IS a distortion afterall

[railhead]

Oh yeah, I don't expect it to be silent -- I'm just gathering opinions.

[Bucksears]

I usually turn the gain up high, then pick very lightly on one of the unwound strings; listen to how the gain fades out and adjust the trimpot until the 'gated' sound is gone.

John's right: the gating is improper biasing. There may be noise due to wiring or whatever, but it's functioning correctly.

LONG LIVE THE BSIAB II!!!!!

[railhead]

Just an update: yep, the bias was just a bit too far off.

FIXED!

[snoof]

nicely done