Here's some mods for the differential distortion

[brett]

Hi.

On the weekend I spent some time messing with the differential distortion.  A couple of simple changes gave a circuit with more punch and distortion than the standard circuit.  It also has a neat thing where it sort of "clamps down" on the early part of the envelope, then lets the volume swell a little and the harmonics blossom as you move into the decay/sustain part of the envelope.  Hard to explain, but I think most people would quite like it.

The components that are different to (or additions to) the standard circuit are in large type on this schematic.


cheers

[petemoore]

Kool Name...I tried to build a Differential, a long time ago, but I never figured it out.
 Nice job on the schematic, I like the shapes in it.

[petemoore]

Could you post some Pin Voltages for Me?
 I can't seem to get it working.
 The PNP's would be facing opposite to Q1, if built on perf but 'like' the schematic?
 I have the PNP Emitters 'on the top', where the arrows are.
 My voltages are strange for the PNPs in an amp position.
 Any Ideas?

[brett]

Hi Pete
The approximate voltages are-
2N3904
C = 4.6
B = 0.8
E = 0.2

2N3906s
C = 0V (actually, it will be maybe 0.1V for the one with the 1k resistor)
B = 4.6V
E = 5.3V

Probably the main thing is to have the 2N3094 collector and 2N3906 bases somewhere near 4 to 5 V.  I agree that the operation of the 2N3906 pair looks weird compared to the usual common emitter amplification stage.  But it does work.

Good luck.

[petemoore]

I'll work on it again tomorrow, and see if I can get something to report on!  It's Bedtime for Bonzo !

[rocket]

if you move the output (including the 1k resistor) to the 2nd transistor,
input and output of the total circuit will be in phase rather than shifted by 180 deg , which might be useful for some purposes.
the sound should not change.
you can even have two output, phaseshifted by 180deg.

[brett]

That's a cool idea.  Now, if you took those two signals and cancelled them, I suppose you'd be left with some distortion products, probably including some octave-up.  Hm... Might have to try something with that.

Anyway, it's not a bad distortion.