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DIY Stompboxes => Building your own stompbox => Topic started by: pinkjimiphoton on March 19, 2012, 08:25:22 PM

Title: dumb hfe/gain in ge transistor fuzzface question
Post by: pinkjimiphoton on March 19, 2012, 08:25:22 PM
hi guys,

real quick dumb question...

i built a ge pnp fuzzface a while ago, for all intents a jh1 fuzz but set up for pnp transistors.

i called it the liberal komrade....it is a really nice, phat sounding pedal.

but...it needs a little more "oomph" in the arse end. i've played with biasing it to get it as loud as i can while still sounding ok, but it's still just a shade above unity when cranked.

i need a little more baalz from it, don't really wanna add another stage.

have tried diode clippers, both ge and si, changes the scream to clean with the guitar knobs too much.

so my question: the two mp16b russkie trannys in there i had matched to about an hfe of 80 or so...

if i were to double that to a higher gain one (i have 'em going up to hfe of close to 300 or so) would it give me more potential output, or just more distortion?

if it will give me more output without screwing with the tone to much, that would be great, but i'm too newb to know.

thanks!
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: rousejeremy on March 19, 2012, 08:50:15 PM
What volume pot are you using?
Fuzz Faces are pretty loud in my experience, they also are louder when biased higher than 4.5 but like you said, they start to sound different.
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: pinkjimiphoton on March 19, 2012, 09:02:13 PM
i forget which pot was stock...maybe 500k?

just checked, yes, 500k.

hmmm...if i replace it with a 250k, do ya think that would do the trick maybe?
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: jrod on March 19, 2012, 09:47:13 PM
If you just need more volume you could change the 330R resistor to 1K.

How do you like those MP16b's?
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: rousejeremy on March 19, 2012, 09:52:57 PM
500k should be good. Try jrods suggestion and let me know how that works, I've never done that myself. Isn't that one of the Roger Mayer mods?
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: LucifersTrip on March 19, 2012, 09:58:36 PM
Quote from: pinkjimiphoton on March 19, 2012, 08:25:22 PM

if i were to double that to a higher gain one (i have 'em going up to hfe of close to 300 or so) would it give me more potential output, or just more distortion?


I think the answer is actually not much of either...it depends on the biasing and surrounding resistors. I can make a pair of 80's sound way louder than a pair of 300's by increasing the 470 resistor or by increasing the voltage on the collector by lowering the 8.2k, but it will sound like crap.

If you adjust both the 80's and 300's to hit 4.5v, then the 300's will probably be a little hotter/sharper... a little volume increase and treble increase.

i would slowly increase the 470 and set it to the max value that you still like the tone.
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: pinkjimiphoton on March 19, 2012, 10:23:27 PM
it's already set with trimmers there i think ...ya know, i'll have to look. pretty sure i already did that, but dear lord, it's quite probable i didn't!
;)

i really like the mp16's...nice sounding, really creamy...in a fuzzface circuit, no less! i don't usually think of fuzzfaces as creamy.

thanks guys,,,i'll try it out and report back!
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: pinkjimiphoton on March 20, 2012, 08:47:00 PM
i checked it out...i had forgotten what was in there...lol ::)

as it turns out, i had a 500r trimmer there.

replaced it with a 1k resistor.

at LEAST twice as much balls...thanks guys!

lu...good call man.

keep illuminating us..

heh heh
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: digi2t on March 20, 2012, 08:50:34 PM
I've always said bro... no such thing as a stupid question  :icon_biggrin:

I'm thinking of building one, with MP20B's, I've got a crapload.
Title: Re: dumb hfe/gain in ge transistor fuzzface question
Post by: pinkjimiphoton on March 20, 2012, 09:01:52 PM
they sound great i bet. it IS a woolier, creamier sound than a standard fuzzface.

i had a 4.7u input cap, but i changed it to 1u...still creamy, but not as wooly.

the 1k resistor is damn near perfect. socket your transistors...i found mine sounds great between about 80 and 160 hfe...not bad with higher gain ones,
but ya gotta play with the bias a little

the liberal komrade uses assymetrical clipping, too...one ge 1n34a on one side, and a 3mm yellow led feeding anothe 1n34 on the other side.

i think you'll like it...but breadboard first. there's a lot of variation to play with!!!
;)

that said, i finally got the stuff coming for the talking pedal and a madbean diphonizer.

soon, as soon as i pay off the last couple orders (all my mad money for the next couple months) i'll get the parts for cousin ludwig, II...  :icon_mrgreen: