UNICORD/UNIVOX SUPERFUZZ - USTOMP LAYOUT

[GREEN FUZ]

This post is intended to serve as a word of warning as much as anything else. Don`t blindly trust in layouts/schematics found on the web. Many are fine, particularly if verified, but others will lead to tears, frustration and even possibly insanity in some cases. You have been warned.

Here`s an example.
http://ustomp.com/?p=12

I chose this layout as I was under the impression, from searching the forum, that many people had used it without any problems, which is why I`m amazed none of this has come up before.
It took me an afternoon of debugging, comparing it to several different schematics, to realise that:

1. 2 of the electrolytics were reversed.
2. The 22k input resistor needs to be after the 10uf capacitor not before it. This created a strange phenomenon whereby turning the guitar volume past 8 caused any sound from the circuit to drop out. Very odd.
3. The 3.3k resistor from lug-1 of the expander/drive pot to ground doesn`t seem to do anything. Removing it and going directly to ground seems to make the drive control operate more as it should although the transition from mild to wild, with nothing in between, is a bit abrupt.
4. 2 of the switch terminals need to be reversed. Alright, that one was my own fault as it does say clearly which terminals go where.


Anyway, it sounds great now. A light overdrive that is extremely touch responsive and perfectly reflects every sensitive nuance of your playing, recommended for Jazz.

You know I`m lying, it`s a Fuzz Monster that obliterates all subtlety and distinction between notes. I love it.

[Mark Hammer]

And lest anyone think that such errors are deliberate or a sign of sloth, do keep in mind that a) even major manufacturers' so-called "factory schematics" can have unintended errors in them, and b) the good folks like Steve and so many others who sweat over layouts they have devised are often working entirely on their own with no one to error-check. 

I can't count the number of occasions I have received requests or seen threads asking someone to please verify a layout that the requester has provided.  It is a sincere request.  I'm sure any one of us here can remember a time when they had worked on something for so long that they would not have been able to see an error in if that error leaped out, bit them below the waist (front and back) and drew blood.  So the request for fresh eyes is legitimate, not a sign of laziness.  Even major companies are not immune to this phenomenon

[ringworm]

Which electrolytics are reversed?
Odd, I built this and have no discernable trouble with it (my uneducated ears ). The expander goes from a soft bluesy fuzz to really harsh (that'll be the 260 hfe transistors i put in) and I don't get any dropouts either, if I turn my guitar level down it just softens the fuzz a little past the '8' point but i figured that for normal behaviour based on the impedence of my guitar pick-ups.
Do the changes make much difference to the overall sound of the pedal? I was thinking of remaking mine with an extra footswitch for the notch and lower hfe transistors.

[GREEN FUZ]

The two electrolytics I found to be reversed on the layout were one at the input and one going to the 22k resistor by the switch. In fairness, and surprisingly, switching them made very little difference to the debugging process. What did was switching the 22k input resistor and the 10uf electrolytic. Doing this cured the weird attenuation problem. As I said, with volume past 8 the sound cut out. At first I thought it was a broken pot on my guitar but using another guitar I still had the same issue. I found that with the 3.3k resistor in place per the layout the expander sounded exactly the same in all positions. Removing it gave me a range of sounds from an octavey "sitar" sound through to full blown fuzz.

I can`t explain why it seems to work fine for you, I`m just relating my experience.

BTW after trying 3904`s and 2N5089`s I settled on BC182`s in the recommended hfe range.

[ringworm]

Thanks for the info. Think i'll give this one another go. I put BC109s in mine, managed to find 6 under 300 and two that matched for the octave. What were the recommended ranges you had?

[GREEN FUZ]

Hey, if it`s not broken, don`t fix it. It sounds to me like yours is working fine.

I read in a previous post that the recommended hfe`s are in the 200-300 range. Mine averaged out around 260.

[DougH]

Always verify a layout against the schematic before you use it.

[jmasciswannabe]

Thanks for pointing this out. I was under that impression, too.  I've got a populated board that I haven't got to wiring up yet. I'll be sure to make the corrections first.

[ustompsteve]

Sorry for the late reply.

I think the layout is correct according to the schematic I used:
http://ustomp.com/files/superfuzzschem.gif

I think there are multiple schematics for the superfuzz.

Mine works great with this layout & schematic.

What schematic are you using?

--steve

[GREEN FUZ]

I cross-referenced several schematics including these.
http://www.aronnelson.com/gallery/main.php/v/Caseys-Vintage-Effect-Page/album34/univoxsuperfuzz.jpg.html
http://www.scribd.com/doc/2474076/UNIVOX-SUPER-FUZZ-VINTAGE-GUITAR-EFFECTS
http://members.fortunecity.com/uzzfay/superfuzz1/usf.html

There is another one somewhere that I can`t find presently.

The one you used seems to be the only one that places the input cap after the 22k resistor. Note the orientation of the electrolytics also.

It seems I am in the minority ( just me? ) of people who have had a problem with your layout so there is the possibility that by reversing those components I simply rectified another problem that was causing the issue. If I was being scientific I guess I`d swap them around again, to see if the issue repeats itself, but now that everything is working I`m loathe to meddle with it.

Perhaps someone better equipped than I could comment as to whether the placement of those two components might explain the symptoms I described previously.

[bside2234]

Thanks for the info. Think i'll give this one another go. I put BC109s in mine, managed to find 6 under 300 and two that matched for the octave. What were the recommended ranges you had?

What 2 transistors do you match for the octave?

I built Steve's version and it seems to work fine but I do agree that the Expander pot doesn't really do anything. Maybe I will try jumpering the 3k3 or maybe even a trimpot on there to see if just lowering the value will make a difference.

I will also swap the input cap and resistor to see if that makes any difference.

[ringworm]

What 2 transistors do you match for the octave?

I built Steve's version and it seems to work fine but I do agree that the Expander pot doesn't really do anything. Maybe I will try jumpering the 3k3 or maybe even a trimpot on there to see if just lowering the value will make a difference.

I will also swap the input cap and resistor to see if that makes any difference.

They were both BC109s with an hfe of 260.

[bside2234]

What 2 transistors do you match for the octave?

I built Steve's version and it seems to work fine but I do agree that the Expander pot doesn't really do anything. Maybe I will try jumpering the 3k3 or maybe even a trimpot on there to see if just lowering the value will make a difference.

I will also swap the input cap and resistor to see if that makes any difference.

They were both BC109s with an hfe of 260.

I meant what 2 transistors like q4 and q5. What two transistors are responsible for the octave effect. I am not getting too much, if any, of an octave effect.

I switched the input resistor and capacitor and it had no affect on my guitar volume knob (not that it did before I switched them) or any other affect at all to my circuit. I then jumpered the 3k3 resistor on the expander pot and that made a huge difference. The pot actually does something now.

As far as the reported hum - I did notice on my SS amps that there was a hum. There wasn't any hum at all on my tube amps. Not sure what causes this. It's not bad though. Just a little noise.

[GREEN FUZ]

I meant what 2 transistors like q4 and q5. What two transistors are responsible for the octave effect. I am not getting too much, if any, of an octave effect.

I believe the transistors responsible for the octave effect are , as you mentioned, q`s 4 + 5. The octave is not massively pronounced with this circuit . More of a perceived thickening of the signal is how I would describe it.  Have you tried monkeying with the bias trimpot?

I switched the input resistor and capacitor and it had no affect on my guitar volume knob (not that it did before I switched them)...

Interesting. I`ll have to swap mine around again, just to satisfy my curiosity.

Thanks for the report.

[bside2234]

That's pretty funny if Q4 and 5 are responsible for octave because I just pulled those out of my a$$.
Anyway, I have the bias pot as an external pot and it does make a difference in the sound. It's just as much as I listen I couldn't hear any octave effect. I was going to try to figure out if I can make it more pronounced. I will keep in mind that it's more of a perceived thickening than a pronounced octave. If that is the case, mine is working perfectly. I may try some different transistors in Q4 and 5 to see what happens.

Maybe someday I will get around to actually boxing this thing up 

I just can't leave it well enough alone.

[jmasciswannabe]

Built it and it works. I left the 3.3k resistor out. Used bc238b transitors except for the last one which is a 2n5088. Sounds great. Trimmed in the octave. I like it a lot. Nasty with a distinct octave sound!