[sdiy] Shruthi 4PM (was re something else...)

[Andrew Simper]

Hi Roman,

What I was getting at is that if you want an ssm2164 to have a
non-linearity most similar to that of a OTA then the placement of the
diodes is important:

http://cytomic.com/files/dsp/ssm2164-non-linear-low-pass.png

The input signal is a +- 5 V sawtooth. The blue plots have no
non-linearity, the red is placing the diode clipper where an OTA has
the tanh non-linearity, and the purple plots are placing the
non-linearity to drain the cap and keep its level bounded directly.
The left plot shows v1 v2 v3 which are the outputs, the right shows v4
v5 v6 which are the inputs that the 2164. Clipping the high pass
signal (input - low pass) is good because it preserves the bass of
your signal while still adding drive. Placing the diode clippers over
the cap is similar to putting your whole signal through a stomp box
after it has been low pass filtered.

All the best,

Andy
--
cytomic - sound music software


On 28 November 2013 16:35, Roman Sowa <modular at go2.pl> wrote:
> I always do that, by placing diodes across one cap in the filter. Keeps it
> from overload and adds some character.
>
> Anyway, I encourage you to experiment with nonlinear elements here and
> there. Long time ago I modified Yamaha CS15 with one 1N4148 in the feedback
> if I recall correctly, and it went crazy. The customer lowed it.
>
> Roman
>
> W dniu 2013-11-28 03:33, Andrew Simper pisze:
>
>> Since everything is so nicely buffered in the 4PM would it be possible
>> (for those that know the 2164 chip better than me) that if you wanted
>> more dirt you could insert a pair of diodes at the input of each 2164
>> to distort the high pass signal that is present there?
>>
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