noisy tonebender Mk II

[mordechai]

I have built a TBM2 circuit that sounds excellent, but the noise/hiss is pretty noticeable and loud (way more prominent than with a Fuzz Face).  Is this just the nature of the beast -- I've never built/played one before -- or is there a way to bring that noise down a bit.  I'm using all metal film resistors and AC125 trannies with low leakage...

[smallbearelec]

I have built a TBM2 circuit that sounds excellent, but the noise/hiss is pretty noticeable and loud (way more prominent than with a Fuzz Face).  Is this just the nature of the beast -- I've never built/played one before -- or is there a way to bring that noise down a bit.  I'm using all metal film resistors and AC125 trannies with low leakage...

The high gain makes it partly the nature of the beast, but the noise/hiss can be tamed considerably with careful construction and choice of devices. Is it on the breadboard at this point? If so, maybe you already know that the noise will go down A Lot once you commit to a board and box it. Do you have an assortment of transistors to work with? The quieter the devices, the quieter the circuit. If possible, it would be worth subbing one device at a time to see which stage is contributing most to the noise/hiss.

[mordechai]

Hi Steve...actually, I figured out the (dumb) problem: I was running it into an already overdriven amp.  I turned the volume on the amp down to 12 oclock and then switched on the effect.  There was still a bit of noise but it was a lot better, and nothing out of the ordinary for such a high gain circuit.  By the way, I subbed out the Q2 for a PNP silicon transistor with an Hfe of 85, got the voltage on Q3's collector to 4.5v, and yowza, did it sound sweet!

[Electric Warrior]

-4.5 at Q3 is very low. I'd expect that to sound very thin and buzzy. Should be around 8.5V.
The trick to get the noise fixed is to make it gate a bit by choosing an appropriate transistor for Q2.

[mordechai]

Getting Q3 to -4.5v was deliberate though, because I get a really cool, nasally but angry sound that had a bit of an octave-up overtone when notes were played above the 12th fret.  A very cool sound, lots of fun, almost synth-like.  But when I biased the circuit properly, it got all of the aggressive, thick tone it was supposed to.  the Q2 is a silicon trannie with an Hfe of 85 and it works like a charm.  I like that this stabilizes the circuit a bit more against temperature fluctuation but it's unobtrusive enough not to really offset the tone that I had with a germanium trannie in Q2 before the switch.