Sonic Distortion derivates

[harmaes]

I own an original Maxon SD-9 and I’m interested to experiment with a number of PCBs which are similar. This thread is to share insights and mod experiences.

I’m going to build an AION Meteor (Mods from the SD9M (mids) and a clipping switch) and the PPCB Samurai (based on Way Huge Geisha Drive).
Except for slight part differences the Samurai has quite different values around the tone pot which should be less shrill and more useable than the original and the Meteor. Not sure if the Samurai has much more gain but seems more fuzzy sounding at higher gain.

The Meteor has red leds as last hard clipping which I’m possibly going to skip if they influence the sound too much. Probably only there to increase output volume.

I’m going to add a clipping switch to the Samurai as I read that people who tried the original mentioning it was too compressed. Maybe 2x2 diodes instead of 1-1 symmetrical could improve on that.

So I’ve noticed some discussions on modding this circuit but not very detailed. I’d be interested in your experiences and what mods you liked and use?

Thanks!

 

[cdwillis]

Edit: don't do this, it doesn't work lol

You can use a dpdt switch to go from one set to two sets of silicon diode clipping:

 

[Feral Feline]

Therwis sumfing awfuwwy skwewwy 'bout dat swihtch diagwam!

 

[cdwillis]

I was trying to be too damned clever lol. I just tested that on a breadboard with a switch and of course it didn't work right. Just put two diodes on one side and four on the other.

 

[Feral Feline]

Get an on-off-on and you can have two types of diodes and no clipping diodes in the middle,
or if you put the highest forward voltage in the middle such as LEDs, the LEDs get ignored when the circuit finds a path of lesser resistance ie when the toggle is in the up or down position.

Here's an idea, when the toggle is...:
DOWN: Symmetrical diodes in the toggle down position (since the bat of the switch points to D3 & D4)
MIDDLE: LEDs will have more headroom than the Si/Ge diodes either side of centre.
UP: Asymmetrical for a different flavour of clipping, even more different if you use different types of diodes than the DOWN-positions diodes — just make sure that D6 & D7 don't have combined higher fV than the LEDs in the middle; also try asymmetrical by having just two diodes but of different types such as a Ge or Schottky with a Silicon diode.

Also make sure your diodes are anti-parallel.

 

[HamishR]

Obviously it depends on the circuit and how they are used etc etc but if we use the TS as an example I have always found that a pair 1N4148/914s sound too compressed. In that example I would usually use 4 x 1N4148s but recent discovered that using a single pair of BAT41s can achieve a similar result. They might be a tad more aggressive sounding, which sounds good to me.

For more texture you might consider trying an extra pair/quad of diodes in a second feedback loop. BJF often does this and the advantage is that it can sound more natural. In a tube amp the distortion occurs over many stages if the amp is well designed, so spreading the clipping over a few stages can help add complexity. It doesn't hurt to put the extra diodes on a switch at first so you can see if they actually do anything!