Fuzz white noise

[b_buerkeli]

Hello everyone,

I'm new here, but I've been building small pedals for a while. At the moment I'm building a Sandlbaster Fuzz aka Holy Grit.
The schematic has a switchable buffer at the beginning, but I built it without.
A ton of white noise is introduced in the yellow-marked area. I tried different low-noise transistors instead of the 2n3053, but the differences are marginal.
What can I do to keep the sound but reduce the noise?

[antonis]

Hi & Welcome.. 

What about Vcc "purity"..??

[b_buerkeli]

Hello antonis,

in the schematic a 51R is in line with the 9V and a 100uF to ground. Increasing or decreasing th 51R did not help. 100uF is sufficient, no?

[antonis]

Is there any chance for Q2 to be flipped..??

Reverse-biased Base-Emitter junctions are excellent shot noise generators..

[GibsonGM]

The 'bias' pots are on DC - I find that causes noise most places I do that.  Any changes in noise if you turn the pots?

[R.G.]

in the schematic a 51R is in line with the 9V and a 100uF to ground. Increasing or decreasing th 51R did not help. 100uF is sufficient, no?

Maybe not. It may well be the wrong kind of cap. For detailed reasons, try putting a 0.01 to 0.1uF ceramic cap across the power supply.

The other reasons presented are valid too; but you may be getting parasitic RF oscillation which can manifest as hiss.

[b_buerkeli]

Is there any chance for Q2 to be flipped..??

Reverse-biased Base-Emitter junctions are excellent shot noise generators..

I can flip the transistor and still get sound (I find that strange) and a little less noise. But I made sure it is oriented correctly, so that is not really it.

The 'bias' pots are on DC - I find that causes noise most places I do that.  Any changes in noise if you turn the pots?

Yes, the bias changes the amount of noise. But also the sound I want to keep.

in the schematic a 51R is in line with the 9V and a 100uF to ground. Increasing or decreasing th 51R did not help. 100uF is sufficient, no?

Maybe not. It may well be the wrong kind of cap. For detailed reasons, try putting a 0.01 to 0.1uF ceramic cap across the power supply.

The other reasons presented are valid too; but you may be getting parasitic RF oscillation which can manifest as hiss.

That I will try.



Thank you all for supporting a novice.

[b_buerkeli]

0.01 to 0.1uF ceramic cap did not change anything.

The most noise is caused, when the fuzz potentiometer is turned up.

[mozz]

There's no Q1! Anyway, try increasing the 47pf, see what that does. If not, try removing the output buffer and take your signal from the base, just to eliminate that as a source.

[PRR]

I can flip the transistor and still get sound (I find that strange)

In a BiPolarJunction transistor, the two junctions are very similar.

In early 1950s parts, sometimes interchangeable, even identical. (There was a thing of doping the C and the E to within a few milliVolts of each other for smooth switching.)

In modern parts the B-E junction will break-down at 7V and the C-E junction has a current gain of 1 to 10. Or over 10V and over 50 used the 'right' way. But in a 9V pedal a 7V breakdown may not happen, and a low current gain does not prove low total gain.

If somehow that part HAS been broke-down by voltage, it will always be hissy. There's a run of early HeathKit g-amps which are now too degraded (stray shocks and static charges) to play without repair.