DOD250 diodes

[amptramp]

This discussion came up in this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=84599.0

and my reply was:

The DOD 250 version in the schematics shown here:

http://www.montagar.com/~patj/dodoverd.gif

uses symmetrical clipping, so you get the fundamental plus odd harmonics and no even harmonics.  The even harmonics give the octaves up from the input signal.  The music note frequencies are shown here:

http://www.phy.mtu.edu/~suits/notefreqs.html

Let's say you play an A at 220 Hz.  Symmetrical clipping will give a third harmonic in the key of E at 660 Hz and a fifth in the key of C#/Db at 1100 Hz etc, which gives you the elements of a major chord spread out over two and a half octaves, so it sounds rather sparse.  Asymmetrical clipping will add the A 440 and A 880 which gives you some towering chords where a lot less is missed and it sounds a lot more like a major chord.  If you swap out one of the diodes for one of a different technology (say, one silicon and one LED), you will get the octaves back which will give you a bit more fullness.

So try your luck with asymmetrical clipping - it should be more musical than symmetrical clipping.

[Renegadrian]

I always put a switch with standard 4148s and red LEDs. I love the LEDs, less distortion but more volume, they really open up the sound...