Transistors in Parallel

[fuzzyfrizzy]

This is my first post, and this is my first effect. Right now (as you can see) this is just breadboarded out. I have it on two breadboards so that swapping transistors would be easier.

This is based on a simple single-transistor fuzz, but I can't remember where I found it online. I have added diodes.

Before I added the diodes, and when I was experimenting with different transistors, I got a "what-if" idea to add a different transistor (of the same type: NPN bipolar) right next to the one I was testing. Electrically, T1's emitter was connected to T2's emitter, T1's base was connected to T2's base and so on.

The tone and distortion characteristics changed some, and the output was a little bit quieter, but some of the combinations sounded really good.

I searched, but I couldn't find anything like what I have done. I'm sure that others have done this, so what I'd like to know is if there are any caveats or tips to make this setup work better.



This shows a tin-can 2N2222 with (I think) a 2N5088: The red arrow points to the transistors.

[mth5044]

Welcome to the forum! I don't know much about what you're experimenting with, but you will get a lot of good reading here and elsewhere if you alter your search to 'piggyback transistors'.

[fuzzyfrizzy]

This is this distortion box which is breadboarded on my bench:
http://www.premierguitar.com/articles/21291-build-your-own-stompbox

There is a downloadable PDF file.

I added various diodes to get smooth distortion, but when I slapped in a set of germanium diodes, it was really sweet.

[PRR]

Paralleling two 50mA transistors gives a 100mA transistor.

Since we never run near 50-100mA in our pedals, what it does to a pedal is un-clear.

That's for identical transistors. If different, it gets more complex.

Alls I can say is: put several sockets in parallel and try any/all combinations.

Obviously you could spend a lifetime running the changes and never actually make Music.

[fuzzyfrizzy]

Paralleling two 50mA transistors gives a 100mA transistor.

Since we never run near 50-100mA in our pedals, what it does to a pedal is un-clear.

That's for identical transistors. If different, it gets more complex.

Alls I can say is: put several sockets in parallel and try any/all combinations.

I have an idea about what may be happening. I suspect that the waveforms combine. If one transistor is maxed out, and is sending harshly clipped output, the other would still have more range, and thus sending an undistorted signal. If the two combine, the clipped waveform would mix with the unclipped waveform, giving rounded waves.

I hate to use the overused term, but that sounds... tube-like.

This calls for a tone generator and an oscilloscope. It seems that the two transistors should be close to each other in value for the best performance.

Obviously you could spend a lifetime running the changes and never actually make Music.

I am more into electronics than playing. I'm on a medication that messes up the memory I need to play, plus I have some arthritis. I do like playing Bach's cello pieces on my Epi EB-0 with flat-wound strings.

[MrStab]

i have little to contribute beyond a fragment of a thought poking the back of my brain, reminding me of something i vaguely read about heat dissipation over parallel BJTs a few weeks ago. here's a lead which, whilst maybe not directly-relevant, could help you dig deeper: http://www.ibiblio.org/kuphaldt/electricCircuits/Semi/SEMI_4.html#xtocid2309425 .

if you want to combine the characteristics of each transistor in a more-controlled fashion, what i would do is split and duplicate that part of the circuit entirely, with one transistor in each half, and sum them. sure, parallel distortions have been done to death, but that's usually with diode clipping. just food for thought - don't change anything if you like the sound as-is!

[dbp512]

OP, have you done any more work/research into paralleling different FETs? I dunno if that just sounds interesting to use newbies, or if theres something in the water, but since reading this, I'm pretty curious about what would happen as well. I just received my first order, I'll see if there are enough parts to make a parallel, or if I'd need to place another order anyway. I want to know what the summation of a clean and clipped waveform would sound like. I'm assuming some kinda od or dist-like sound, without as pronounced effect.