Looking into doing a Fuzz pedal and never dabbled before what transistors to use?

[mort]

What replaces 2n2614, 2n2613, or 2n270?


Also, what do I need to know about transistors in a nutshell? I know it's a broad question but I'm just looking for a starting point on how to understand them. Thanks for any help.

[52 Bill]

All of the numbers that you listed are Germanium transistors, which were the most common types when transistors were first introduced. Modern transistors are Silicon types. The two types can be interchanged, but the circuits will need to be altered to allow for the different biasing needs.

Transistors can be thought of as similar to tube triodes. The Collector would be the plate, the Emitter the cathode and the Base the input grid. In most circuits the power supply will connect to the Collector, the Emitter will connect to ground either with or without a resistor and bypass cap and the signal will be applied to the Base. In most cases the base will need to be biased on with resistors.

And just like tube stages the signal from the collector is 180 degrees out of phase from the input and in phase at the emitter.

What sort of pedal are you looking to build?

[Mick Bailey]

You can look transistor equivalents up on Alltransistors.com. Ge circuits are pretty flexible and almost anything (so long as it's Ge) can be substituted in fuzz pedals and give good or excellent results without changing anything else in the circuit. There are plenty of online resources to learn transistor basics.

The 2N270 is and exception and is perhaps one of the most difficult transistors to find an equivalent. The device has very poor leakage characteristics and this enables it to self-bias. If you build a circuit designed around this device (such as the Maestro FZ1) it is unlikely to work correctly without further modification if you substitute anything else.

[jbltwin1]

If you're interested in fuzz and other effects, go here: Guitar FX Layouts and poke around. A LOT of projects. Mike.

[mort]

Yeah I'm gonna start off with a maestro circuit and go from there.. Was looking at the Fz-1a and some googling for transistors lead me to the 2n404. Is that a comparable part?

[52 Bill]

Yeah I'm gonna start off with a maestro circuit and go from there.. Was looking at the Fz-1a and some googling for transistors lead me to the 2n404. Is that a comparable part?

Yes, that is another Germanium transistor.

Small Bear electronics sells calibrated sets of transistors to build the FZ1-A, or at least they used to. They also have instructions on how to bias that circuit as well.

[mort]

ok so here we are a year later and I'm ready to get moving on this idea.

The transistors that I have are the 2n404 type. I have a few that I've had since last year and ordering more so I can do two of the exact same pedal. One will be a gift and one I will keep.

After some more googling around I decided to go with a Fuzz Face type circuit and came up with this drawing which I believe is the earlier positive ground version



I don't know what type of transistors this drawing was designed around, but does it appear that I will need to change any values to employ the 2n404's?

[frus]

there's a handy calculator here:

Analog Alchemy - EMH

(click the Fuzz Face link on the left)

You'll have to measure the real gain of your transistors though

[mort]

ok I plugged in numbers from the above drawing and I got 72 and 76 from the person that sold them to me as he labeled each one with their particular gains, and it spit out very close to the 33k s I built it exactly as above but with a switch in it. I suppose it sounds right. I'm not very experienced with pedals at all, being more of a straight in type player.

And the 33k is what I'd adjust in order to drive it harder or softer? I don't think I would want to drive it any harder though, if anything maybe calm it down a bit.

And one thing that occurred to me.. maybe it would be nice to have a pot that would blend in dry signal into the wet signal. Would the wet just overpower it anyway? Any thoughts on this approach?

[mort]

another question, is that correct that the 20uF cap gets its positive tied to ground or is that a mistake in the drawing?

[eschertron]

another question, is that correct that the 20uF cap gets its positive tied to ground or is that a mistake in the drawing?

You did point out that it was positive ground.

Also, since I see "R.G.Keen" on the watermark for the circuit, you could ask him for suggestions. I'm pretty sure he'd get back to you on it.

[mort]

You did point out that it was positive ground.

Also, since I see "R.G.Keen" on the watermark for the circuit, you could ask him for suggestions. I'm pretty sure he'd get back to you on it.

I thought about that some time after making the post

Started wondering if there was an easy way to improve bass response on it... or maybe alot of bass response is bad in a fuzz pedal??

Listen to this clip.. when the effect gets switched on you can hear the bottom drop out. The effect still sounds great though..

https://soundcloud.com/mortatone/coyotefuzz1

[eschertron]

Thanks for sharing the link!
There's a lot to like about any 'fuzz' effect. Aesthetic is in the ear of the beholder, right? Each of us has the tone that we prize most; until we hear another tone that's more novel than the last! If you wonder about the freq response of the unit under test, play with components until you hear something you like more. And using pots to allow dialing in a sound, then fixing the desired value, is a respected design technique. If your curious how the 33k affects the signal, put a 100k pot in its place, after setting the pot to start at 33k. Keep in mind that too low a value will burn up Q1, so care needs to be taken when working with those rare and expensive Ge devices.

The fuzz pedal I use is a Way Huge Swollen Pickle - 5 potentiometer controls on the front, and if that weren't enough, two more hidden inside the case! IHMO there's no limit to what musicians can do by shaping the tone of the fuzzed-out signal. Certainly more than just feeding it through a foot-operated variable-cutoff band-pass filter!

[smallbearelec]

I was not clear from the post whether this was already a soldered build. If so, and you like what you have, great! If you are still seeking the tone you want, learn to use a solderless breadboard:

Using A Solderless Breadboard''

The silicon FF is cheaper to build and easier to tweak than the germanium version, and it is more friendly to a modern pedalboard.

[mort]

The guy I built this for is asking me for a silicone version. Can I just drop in the different transistors or do I need to make any other changes?

[eschertron]

...asking me for a silicone version...

I'd go with 38DD

edit: sorry, mort. Couldn't resist!