Superfuzz volume problem

[Chrissie]

A few months ago I built myself a Superfuzz clone based on this schematic: http://www.univox.org/pics/schematics/superfuzz.gif
It sounds really nice, and I have used it for several recording sessions.
I'm planning to use it live, but it has one problem: the pedal has a lack of volume, it hardly reaches unity gain.
Is that normal? I never played an original Superfuzz.

I already checked all components and nothing seems wrong.
Below are the transistor voltages, which also seem ok.

Any suggestions?

Q1
C 5.68
B 0.71
E 0.11

Q2
C 8.71
B 5.67
E 5.03

Q3
C 5.92
B 3.36
E 2.75

Q4
C 3.12
B 1.84
E 1.20

Q5
C 3.12
B 1.84
E 1.20

Q6
C 6.01
B 1.03
E 0.39

[MikeH]

Try flipping your transistors around.  I learned this recently; the trannys in the superfuzz will work backwards, just not as efficiently.  The result is good fuzz, but low output.

[JasonG]

I would say double check how you have the pots wired/ grounded. How did you build it pcb or vero ?

[Solidhex]

Yo

  Hmmmm your transistor voltages are good. I once repaired an original Superfuzz that sounded incredible but had very low output. There are usually a decent amount above unity gain though.

--Brad

[Chrissie]

Yo

  Hmmmm your transistor voltages are good. I once repaired an original Superfuzz that sounded incredible but had very low output. There are usually a decent amount above unity gain though.

--Brad

Thx brad, how did you solve the problem with that one?

The orientation of the transistors are correct.
I tried it wih several types, but measurements were taken with 23904's

[MikeH]

Can you post a link to the layout and schematic you used?

[Chrissie]

Can you post a link to the layout and schematic you used?

Layout: http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/superfuzzboard_final.jpg.html?g2_imageViewsIndex=1
Schematic: http://www.univox.org/pics/schematics/superfuzz.gif

[MikeH]

I don't know what the gain of a 2N3904 is compared to a 2SC828, but if it's a lot less that could be the reason, however I don't think it is.  If your transistors are socketed it would be worth it to flip them around and see.  In this circuit, when they're backwards they conduct, and the voltages even look reasonable, but the output is low.

Here's a quote from RG regarding this:

Originally, there was no difference between collector and emitter junctions. Later we found out that if you make the emitter junction really thin and small, it give more gain and higher breakdown voltage, so you can make the collector junction more burly. But they still show transistor action at below the emitter-base breakdown voltage, which is usually 6-10 volts depending on the device. Yours both have a "collector-base" voltage of less than 6V, so it's possible they work this way, albeit more poorly .

So it could be possible that even one of them is flipped and it will still work.

[Chrissie]

I just tested it... Flipping the transistors wasn't a solution.
Most of them lowered the volume even more when reversed...

[MikeH]

Well then!  We can rule that out...

Have you looked at a datasheet to check the gain of a 3904 vs an 828?  I ask because I don't know, not because I think it's a possible solution.  Someone also mentioned pots before- check that you have the right value.

[Chrissie]

owkay, I got hold of a bunch 2sc828's: I did put them in the pedal, but they didn't solve the volumedrop.

The voltages are very similarwith the ones posted in my first post (2n3904's)

So, what's next I can check to find the problem?

[bluesdevil]

Hello - I built one recently and had the same volume drop problem. Putting a 22uf electrolytic bypass cap parallel to the emitter resistor on the last transistor did the job....loudly!! The cap's negative leg goes to ground and the positive leg goes to the emitter.
      Higher cap values gets more bass, so experiment for the tone you like. I like mine on the heavy side.
                  Good luck!!!!

[spaceace76]

have you messed with the trimpot at all?

I had a similar problem and it turned out to be a solder splash (sorry... I can't remember where...) so the best advice I can give would be to double check the cuts on the vero, and check that nothing has been bridged.

[tjmicsak]

Check on the BYOC Leeds Fuzz for that schematic. I think you need electrolytics on all the 10uf caps. See if that helps.
The trimpot should be adjusted to give the most background noise, which should be about middle setting.

[R.G.]

Pinout, soldering, wiring;
pinout, soldering, wiring;
pinout, soldering, wiring;
pinout, soldering, wiring;
pinout, soldering, wiring;
pinout, soldering, wiring;
pinout, soldering, wiring;

Note: the 2N3904 and 2SC828 do NOT have the same pinout.