Univox superfuzz hissing !Need help!

[Filip_Mikuz]

hi!

So ive built a clone of the univox super fuzz and im having trouble with outrageous hissing. it has something to do with the 9v power supply, because the the hissing is minimal yet still audible on a battery. And the noise is also connected to the volume and gain or in this case the balance and expander. i made the effect acording to this schematic, but i left out the polarity protection because i dont think its important.

thank you for your help

[kaycee]

Sometimes hissing can be a poorly connected transistor, or indeed one damaged by overheating if you soldering isn't up to scratch.

Another thing, on high gain pedals, wire the circuit input to ground when switched out. And, also keep the input and output wires away from each other. See if any of those ideas help.

[PRR]

Welcome!

Which knobs affect the hiss?

Did you use a kit or work on perf? Any voltages in there?

The Debugging page really helps the process by asking the Usual Questions.

[PRR]

> i left out the polarity protection because i dont think its important.

Oh, wait. Did you "leave out" the 100 Ohms and 100uFd??

That's power-crap filter. A bad supply, without this filter, will give bad result.

[Filip_Mikuz]

i didnt use a kit, but i checked the schematic and apart from the 2n2222(in the original they use 2sc539 and 2sc828) everything else is the same. both nobs affect the hiss even the tone on the guitar. And no i didnt even built that 100uf filter, ill try today and get back to you later.

[Filip_Mikuz]

OK that filter definitely helps a lot (i can a least play it now with out hearing so much of the hissing), but theres still a big difference between 9v supply and battery. the battery gives off a little buzz that barely hearable when idle. the 9v on the other hand still hisses. is that normal? in a band setting its probably not audible but i still hear it.

[DiscoVlad]

That looks like my schematic! 
I don't remember when I drew that, but I've never managed to get a working pedal from it, so there may be some bugs... It was based on This schematic adding in reverse polarity protection, input pulldowns, and improving the supply filtering.

Anyway, If the hiss is because of noise from the power supply, increasing C16 to 220uF should help (that would drop the corner frequency of the supply filter to about 7Hz, from 15Hz). If the hiss is just because it's a high gain circuit picking up external noise, or there's a problem with the layout/wire routing this probably won't help.

On some original pedals Q2 and Q3 were 2SC828. These are lower noise transistors than the 2SC539 used in the rest of the circuit, other versions had all 2SC828 transistors.

[Filip_Mikuz]

Oh cool. Well i can post a video of the thing working if you want. I will also try that 220 if it works any better

[duck_arse]

filip - does your hiss lesson when you rock the octave timm pot either side of best sound?

and that circuit looks ok to me, disco, the errors must be "elsewhere". and if you were on a breadboard, you could try isolating Q1's supply (or maybe Q6) from the rest of the circuit with another DC bypass R/C. maybe.

[DiscoVlad]

filip - does your hiss lesson when you rock the octave timm pot either side of best sound?

and that circuit looks ok to me, disco, the errors must be "elsewhere". and if you were on a breadboard, you could try isolating Q1's supply (or maybe Q6) from the rest of the circuit with another DC bypass R/C. maybe.

From memory it was a combination of mixed up transistor pinouts, and bad soldering.

Looking around both here, and other forums it seems to me that hiss is an inherent part of the Superfuzz sound - The circuit is quite high gain which means it's going to be noisy, but maybe some combination of shielding, metal film resistors and low noise transistors would help... Or it's just a thing you'll have to deal with.

[Filip_Mikuz]

it was my first build anyway, i am planning to build another one with much more attention to detail. if the problem persists i will try to test it as much as i can and i will get back to you. but thanks for all your help. ive also provided you with a video of the hissing before the filter on the polarity protection was installed. at this point the hissing is much quiter than in the video but still behaves the same. take note, in the video i first raise the second pot (balance) and then the first one (expander). and no, the octave trim doesnt do anything.

[bloxstompboxes]

You have a plastic enclosure sir. Try using a metal one and a lot of that noise should go away.

[R.G.]

OK that filter definitely helps a lot (i can a least play it now with out hearing so much of the hissing), but theres still a big difference between 9v supply and battery. the battery gives off a little buzz that barely hearable when idle. the 9v on the other hand still hisses. is that normal? in a band setting its probably not audible but i still hear it.

There is a compendium of things.

(1) High gain amplifiers, as noted earlier, amplify any tiny noise up. A lot. Signal is clipped off so it doesn't get louder, but the noise is usually below the clipping level, so the noise gets relatively louder compared to the signal. It's the nature of the beast.
However...
(2) if it gets much quieter with a battery, then (1) isn't it. Hiss based noise from amplification doesn't go down with battery power. "Little buzz that's barely hearable" is where the pedal *can* get.
(3) Big, in-your-face hiss is sometimes caused by the pedal oscillating at RF and the phase jitter of the RF oscillation being heterodyned down into the audio as an angry-sounding hiss. This might fit with your description, especially since
(4) You left off the power supply filtering because you didn't think polarity protection was important.
(5) even with the electrolytic cap filtering from the polarity protection put back in, electrolytics aren't too good at filtering very high frequencies because of the way they're made. So it would be a good idea to get a 0.1uF *ceramic* cap and bypass the collector of Q2 to the ground at the bottom of R6; this is the most likely place to be generating RF, so that is the likely place to kill it. The cap from Q2 base to Q2 collector is there to suppress RF response, BTW.

That may help.