[sdiy] MS 20 FILTER

[harrybissell]

I'd say that the MS-20 never clips nicely. Its more a wild beast...
more "touch tone telephone" sound than "acoustic" imho.

The Sallen-Key type filters are hard to tame. They like to oscillate if
they
can. The most interesting feature is that when the resonance /
oscillation
starts, it starts at the zero cross. Most other filters resonate at the
peaks
of the wave. This might affect the following stages (VCA etc).

Interesting filter. Not my favorite, but interesting

H^) harry

Colin Raffel wrote:

> Hey Diago,
>
> That symbol, the two circles, signifies the OTA's current-based
> amplification feature.
> Vr is the reference voltage, in a single supply circuit such as this
> one, this means 1/2 of V... by using Vr as ground and ground as V-,
> it simulates a dual supply system.  Vr in this case is around 4.5 v,
> and is generated by the top right little circuit there with two LEDs.
> That buffer circuit is built into the LM13600.
> Read up more on the LM13600, it is a very useful chip!  You can refer
> to the LM13700 datasheet-it is the same in structure with a slightly
> different built in buffer.
> http://www.experimentalistsanonymous.com/diy/Datasheets/LM13700.pdf
>
> A note about the circuit you are referring to-I have found that it
> clips very ugly, the MS20 filter I think is supposed to sound nice
> clipping... I believe that's because Tim E's implementation is
> designed for 9v (pedal use) and makes some sacrifices.  I have never
> tried this circuit, but this one supposedly reflects the real MS20
> filter more.
> http://www.uni-bonn.de/~uzs159/rs20.png
>
> -Colin
>
> On Dec 17, 2005, at 11:02 PM, synth DIY wrote:
>
> > hi! i have this MS 20 filter project to do and i've been have some
> > problems:
> >
> > in this schematic i don't really understand the meaning of the
> > symbol in the output of U1a and U1b.
> >
> > "Vr" voltage is the ground voltage?
> >
> > between pin 7 and 8 ( and 10 and 9 ) it's a buffer circuit. should
> > i use any specific kind of buffer?
> >
> > Lm 136000 datasheet is not available, but i found a  http://
> > www.datasheetcatalog.com/datasheets_pdf/L/M/1/3/LM13600.shtml.
> > is it the same?
> >
> >
> > thanks
> > Diogo
> > <sk.gif>