Univox Superfuzz users / builders. Need help

[Atodovax]

Hello everyone. I built a couple of Superfuzz pedals all uding different layout but It seems im having the same issue with all of them. When i play a chord and inmediatly mute the strings i can hear a fainting repeat like a delay with one feedback rising and disapearing. So it s like i pluke the strings and them i hear a repetition of that sound faintly... Im using low gain transistors 80hfe and i recall only one of the Superfuzzed that i built didnt do this when using high gain transistors. Any ideas? Is that sound to be expected? Do originals do the same? Im using only batteries

[Atodovax]

Apart from the "delayed" noise coming when i mutr the strings the pedal sounds totally killer with lots of octaves blooming

[Derringer]

I've built 4 superfuzzes and have never noticed this affect you speak of

Perhaps you were in a spinning room and were just hearing a doppler affect of sorts?

[Atodovax]

I've built 4 superfuzzes and have never noticed this affect you speak of

Perhaps you were in a spinning room and were just hearing a doppler affect of sorts?

Ha ha ha id love to have a room like that. Do you remember what hfes did you use? For some reason this is happening when using low gain transistors It seems...

[GibsonGM]

Can you record and post the sound??

[PRR]

> Perhaps you were in a spinning room

Don't laugh. One summer, on another forum, lots of folks reported swirly sound. We learned to say "Turn off the ceiling fan!" before exploring complicated theories. About 9 of 10 WERE a ceiling fan.

[Atodovax]

Can you record and post the sound??

Im going to record it tomorow and post it here. Its actually not a repeat as i Delay pedal would do but more like a HUM background noise that rises when i stop playing for a second and then decays... very strange.
Its like this: I stroke a chord and inmediatly mute the guitar and the Hum comes next and desapears.
Craaaaaaaaank (guitar chord) "mute" hhhhhHHHHHUUUUUUMMMmmmmmm... Silence... I hope that makes sense ha ha ha

[Atodovax]

> Perhaps you were in a spinning room

Don't laugh. One summer, on another forum, lots of folks reported swirly sound. We learned to say "Turn off the ceiling fan!" before exploring complicated theories. About 9 of 10 WERE a ceiling fan.

Haha thats awesome... But believe me.. Everything is just fine here. I built a coupleof this circuits and this only happens using low gain transistors (hfe 80 more or less)

[Fancy Lime]

I've never built a Superfuzz but I think I recognize the problem. I have only ever experienced this with high(ish) gain stages with a fairly small input coupling capacitor and a large bias network resistance. If I increase the cap size or reduce the bias impedance, the strange effect, which I would describe as a kind of "after WHOOOP", goes away. What I think happens is that the base of the transistor sucks all charge from the input cap and the bias network cannot keep up with biasing the base. Therefore, the transistor goes out of bias on loud signals, which sounds great on a fuzz (to my ears). If the cap is large, this does not happen easily because it acts as a charge buffer. If the base is biased with smaller resistors, they can quickly supply enough charge to counter the "charge sucking" by the base. After the note stops (with a small cap and large resistor), the base returns to the proper bias point with some delay because the cap needs to be filled also. This sudden rush of current creates noise which is amplified.

Mind you, this is just what I conjecture happens based on my own experimentation with a phenomenon that I assume to be the same as you describe. So no guarantees that it has any bearing on your case or is correct at all. But do try increasing the input coupling caps of the higher gain stages by a factor of 10 and see if it goes away. The fact that the problem seems lessened with high gain transistors would make sense if my explanation is correct because they tend to suck less current into the base under the same conditions.

Hope that helps,
Andy

[duck_arse]

please post the circuit diagram you are working to, that we might see the value of your coupling caps. and if they are oriented correctly.

[Derringer]

I've built 4 superfuzzes and have never noticed this affect you speak of

Perhaps you were in a spinning room and were just hearing a doppler affect of sorts?

Ha ha ha id love to have a room like that. Do you remember what hfes did you use? For some reason this is happening when using low gain transistors It seems...

I think I was using high gain Q's. 2n5088s maybe even 89s

[Atodovax]

I've never built a Superfuzz but I think I recognize the problem. I have only ever experienced this with high(ish) gain stages with a fairly small input coupling capacitor and a large bias network resistance. If I increase the cap size or reduce the bias impedance, the strange effect, which I would describe as a kind of "after WHOOOP", goes away. What I think happens is that the base of the transistor sucks all charge from the input cap and the bias network cannot keep up with biasing the base. Therefore, the transistor goes out of bias on loud signals, which sounds great on a fuzz (to my ears). If the cap is large, this does not happen easily because it acts as a charge buffer. If the base is biased with smaller resistors, they can quickly supply enough charge to counter the "charge sucking" by the base. After the note stops (with a small cap and large resistor), the base returns to the proper bias point with some delay because the cap needs to be filled also. This sudden rush of current creates noise which is amplified.

Mind you, this is just what I conjecture happens based on my own experimentation with a phenomenon that I assume to be the same as you describe. So no guarantees that it has any bearing on your case or is correct at all. But do try increasing the input coupling caps of the higher gain stages by a factor of 10 and see if it goes away. The fact that the problem seems lessened with high gain transistors would make sense if my explanation is correct because they tend to suck less current into the base under the same conditions.

Thanks for the great reply. I think this is exactly the problem im experimenting. The thing is i dont want to change or modify the circuit at all. Thats why i want to know if this also happens on original units. I read once that transistors should be low gain thats why i tried 2sc828T on them (hfe 100 or less) if i use 828R (hfe 300+) i dont get this effect (or at least is very subtle) but the sound is more harsh. The sound i hear coming in and out right after muting the strings after i smash a chord is noise.. Not delayed signal. Just noise being amplified and reduced in a couple of miliseconds

Hope that helps,
Andy

[Atodovax]

please post the circuit diagram you are working to, that we might see the value of your coupling caps. and if they are oriented correctly.

I tried both the General Guitar Gadgets pcb layout / schematic and the Effectslayout pcb layout. Both behave the same way with low hfe transistors.

[pinkjimiphoton]

I've never built a Superfuzz but I think I recognize the problem. I have only ever experienced this with high(ish) gain stages with a fairly small input coupling capacitor and a large bias network resistance. If I increase the cap size or reduce the bias impedance, the strange effect, which I would describe as a kind of "after WHOOOP", goes away. What I think happens is that the base of the transistor sucks all charge from the input cap and the bias network cannot keep up with biasing the base. Therefore, the transistor goes out of bias on loud signals, which sounds great on a fuzz (to my ears). If the cap is large, this does not happen easily because it acts as a charge buffer. If the base is biased with smaller resistors, they can quickly supply enough charge to counter the "charge sucking" by the base. After the note stops (with a small cap and large resistor), the base returns to the proper bias point with some delay because the cap needs to be filled also. This sudden rush of current creates noise which is amplified.

Mind you, this is just what I conjecture happens based on my own experimentation with a phenomenon that I assume to be the same as you describe. So no guarantees that it has any bearing on your case or is correct at all. But do try increasing the input coupling caps of the higher gain stages by a factor of 10 and see if it goes away. The fact that the problem seems lessened with high gain transistors would make sense if my explanation is correct because they tend to suck less current into the base under the same conditions.

Hope that helps,
Andy

i think i agree. i've found fuzzes do some weird stuff... like a harmonic perc circuit i built... pull one of the q's and it would keep working... until the cap discharged. super weird. but i think andy got it, or is close.

[willienillie]

I read once that transistors should be low gain thats why i tried 2sc828T on them (hfe 100 or less) if i use 828R (hfe 300+) i dont get this effect (or at least is very subtle) but the sound is more harsh.

AFAIK, the Super-Fuzz used the same transistors as the Uni-Vibe, 2SC539 and 2SC828.  I don't know about the '539s, but all of the '828s I've seen clear pictures of have been "Q" marked (hFE 130~260).  Below the Qs were the Ps, not sure if they went down to O, but Ts would be higher gain if they made those.  The Panasonic datasheet only lists QRS, but I know Matsushita offered Ps because I have several, some measuring down in the 60s.  The few Qs I have measure around 175~200.

[pinkjimiphoton]

i use 828's in mine. forget the range, but bought a big bag a few years ago.

[Atodovax]

Im getting trouble trying to record a decent audio sample but after socketing each transistor i can now affirm that going high gain on hfes reduces this effect. Its like the low gain transistors were gating all the noise when the guitar is playing and right after muting the strings the noise rises and falls in a second

[Atodovax]

Psu capacitor was originally smaller than 47uf but i wouldnt think the problem is there right?

[rutabaga bob]

A weird problem.  I made one with lower hFEs and it worked fine.  Dino made his with gains of 100...posted on here somewhere..and he swears by it.  Wish I could help you more.