1.5V fuzz pedal

[C Bradley]

I'm working on a 1.5V AAA powered fuzz pedal. I had a couple of tiny dome shaped pieces of plastic around and wanted to see if I could build a pedal in them, so I came up with a circuit. It's a 2N3906 transistor with a 2k2 collector resistor, emitter is grounded, bias is set with two 100k resistors from the power supply to ground and the junction is connected to the base of my transistor.

It works and distorts the signal, and I can get a good bit of volume out of it, but it's too clean for my tastes. I'm going to try some germanium diodes on the output to clip the signal. Any other ideas on how to get a bit more distortion out of this thing?

[MartyMart]

Played with the 2k2 value yet ??
Couple of 1N34A's at the back end will help....

Marty.

[C Bradley]

The 2k2 holds the collector close to .75V so I can get a symetrical wave at the output. A 2k4 would be ideal, but I don't have one of those. I've tried a 1k on the collector, but I like the 2k2 better.  

I'm off to Radio Shack to find those 1n34's.

[Sir H C]

Hard to get regular diodes to clip much with a 1.5V rail.  Schottkeys or Germaniums would work better.

Also you can do several stages of these and get a lot more gain.

Finally, often you will see these devices biased with a single resistor from the base to the collector (or rail).  This is a better way to bias when not using an emitter resistor.

[MartyMart]

Hard to get regular diodes to clip much with a 1.5V rail.  Schottkeys or Germaniums would work better.

Erm, 1N34A's are "Germaniums"   :wink:

Marty.

[Hal]

take a look at the bazz fuss circuit...just an idea, but I wonder if you could work with that config - IIRC, it uses a diode for feedback.  Try a Ge ?

[DDD]

Put 6,2k to 10k resistor instead of 2,2k and adjust the "upper' 100k till the collecror voltage reaches 0,75V.
Gain will be higher - more distortion.

[jmusser]

If you find 1N34s at Radio Shack, let me know, because as far as I know, they quit selling them about 5 years ago! Aron can fix you up with some for sure.

[RandomRedLetters]

The second transistor stage will clip the wavefore asymetrically. It'll sound a bit harsh but it'll do the job if you cant get germanium diodes.

[RandomRedLetters]

oh and yeah I agree with throwing some 1N34a's on the back end as well.

[petemoore]

100k's from emitters to ground?

[C Bradley]

100k's from emitters to ground?

That looks like he's got them from the collectors to ground, with +1.5V going to the emitter via the 5k resistors. The bias looks wrong to me.  :?

I didn't make it to Radio Shack. I would have made me late for work. :roll: I'll try a 10k on the collector and adjusting the upper 100k until it's biased right. Thanks for the advice!  

[Brian Marshall]

The second transistor stage will clip the wavefore asymetrically. It'll sound a bit harsh but it'll do the job if you cant get germanium diodes.

this doesnt look like it will work... unless you are trying to use those transistors as negistors.  Also for PNP the resistors look right for gain, but the negative feedback should go to the collectors and not the emitters.  Also youll need some caps in there to get rid of DC offset.

[Sir H C]

The second transistor stage will clip the wavefore asymetrically. It'll sound a bit harsh but it'll do the job if you cant get germanium diodes.

I would say, flip the 5k and the 100k, concider the transistors NPNs and put a cap on the input and output and you have a circuit.

Two followers won't give voltage gain.

[C Bradley]

Made a trip to RS; no 1n34's or any germanium diodes. No single AAA battery holders either. Looks like I'll be sending an order into Mouser. If I can get a stereo 1/8" jack I can do without an on/off switch, and I'm guessing that with the 1n34's I can do without a volume pot since the output will be limited to 200mV peak-to-peak. That will free a little space inside my enclosure, but I'd still like to have a bypass switch.

[Hal]

check out tiny 12v lithium batteries

[petemoore]

For the battery connections, what I do is run V+ and V- wires from the middle to the outsides of the battery: -l<--->l+, taping each wire so the deinsulate ends go over the battery connectors, then tape all the way around the batery making sure the little loops I bent are touching the battery connectors, works fine. I just untwist a wire splice between battery and board on the ground side to disconnect.