Transistor as Clipping Diode?

Started by Wonderdog, January 25, 2010, 10:33:53 AM

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Wonderdog

I took two basic silicon transistors, joined the right and center legs, and put them in place of 1n914 clipping diodes and it sounds really good.
Why does this work?

R.G.

Because internally all =>> bipolar<<= transistors ARE diodes. There is a collector-base junction, and a base-emitter junction. Connecting any two leads together and using the shorted two and the remaining one will result in it looking like a diode.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

Wonderdog

Cool.  I used it to replace to red led's.  It sounds great.  Does it change the sound depending on which two leads are joined?

Also on another pedal I clipped the middle lead and just used the outer two.  Smoothed out the sound.  What is up with that? Same thing?

kurtlives

Makes good use of your old leaky/low gain Ge transistors! :D
My DIY site:
www.pdfelectronics.com

Wonderdog

Quote from: kurtlives on January 25, 2010, 02:08:28 PM
Makes good use of your old leaky/low gain Ge transistors! :D

Yep, I scavenged these off an old effect board.  Two different transistors, didn't care, just took out the first ones I found.  Maybe the difference gives a little asymmetric clipping.

edvard

I've done this before but short the base lead to collector:
http://sci.tech-archive.net/Archive/sci.electronics.components/2007-02/msg00109.html
QuoteThis is sometimes called a "super diode"; it has a maximum current
rating equal to the maximum collector current of the transistor, and
tends to have a nice low forward voltage drop at moderate currents
compared with average small signal diodes...

I read about this first in an old electronics text I can't remember now (ARRL handbook maybe?)
I don't know exactly what that means to guitar signals, but I know they sounded pretty good as feedback or clipping diodes in your standard single-op-amp distortion box.
All children left unattended will be given a mocha and a puppy


aron


Wonderdog

#8
I did some measurements yesterday:

JFET 2N5458  xster:  Gate/Source shorted - .37 Vf   -     Measure across Gate/Drain - - .7Vf.

I think