Fuzz Face Clone Noise???

[Jasonmatthew911]

Hey guys, I just built a Fuzz Face clone for fun, and it works fine, except for some loud background noise, that is heard mostly when not playing the fuzz...I followed the classic fuzz face schematic, but I replaced the 1K Fuzz pot with a 1K fixed resister and a 22uf Cap, so I just have a Volume knob...When my Volume is all the way up, the noise is obviously louder....Any idea how I can get rid of the extra noise?...I'm also using BC108 and BC109 Silicon transistors....I saw someone put a 1K resistor at the input, what does that do exactly?....I added a 100uf Cap on the +9V rail but that doesn't get rid of the extra unwanted noise either....Any help?

[Scruffie]

The 1k on the input is a bit like rolling down your guiitar volume.

Is it noisey when run on a battery? That'd rule out the power supply being the issue. A series resistor from 9V (47R?) with a large (100uF?) and small cap (100nF?) to ground may help filter out some noise if it is.

[Jasonmatthew911]

The 1k on the input is a bit like rolling down your guiitar volume.

Is it noisey when run on a battery? That'd rule out the power supply being the issue. A series resistor from 9V (47R?) with a large (100uF?) and small cap (100nF?) to ground may help filter out some noise if it is.

I'm using a Boss PSA-120S power supply, and I have a 100uf Cap on the 9V rail going to GND...I basically have a really loud hiss as soon as I stop playing the fuzz, but while I play you can't really notice the hiss....

[joegagan]

many people have run into this when building SI fuzzfaces. the higher gain transistors sometimes need some taming to make the treble less harsh, less hissy, etc. search out fulltone 70, silicon fuzz face, etc. people put small caps across base to collector and sometimes caps to ground to tame things.

gus smalley's JH2 MOD is the coolest Si fuzzface i have tried. it has more components than a stock fuzzface, but very worthwhile additions.

[joegagan]

power supply probs usually cause hum, not hiss in my experience, but it is always a good idea to sub in a battery to see how it compares anyway.

another good article on silicon fuzzface, old but still applicable

http://www.home-wrecker.com/sili-face.html

[Jasonmatthew911]

I put a 500pf cap from base to collector of Q1 and it got rid of most the hiss actually...Thanks guys...

[LucifersTrip]

I put a 500pf cap from base to collector of Q1 and it got rid of most the hiss actually...Thanks guys...

i would suggest slowly reducing that and choose the lowest value that still gets rid of the hiss. you probably want to tame it as little as possible...a 100 - 200pf usually works