ASM-1 as an analog filter?

[Gene & Debby Stopp]

The VCF section (and all the module sections, for that matter) are
independent and easily built by themselves. Some may call it a waste to
only use an ASM-1 for the VCF, but I believe that all of us project
builders have a goal with a price tag we'll accept and that's all the
justification you need!

The state-variable type of filter (which the ASM-1 has) is well known for
its raunchy sound when overdriven, especially as the Q is turned up. It's
the nature of the beast. If you want nice clean sounds with lots of
resonance with this type of filter, you will need to keep the input signals
down way below standard synthesizer module levels (like below a volt p-p).
This is usually discovered by accident as the synthesist creates a
perfectly normal patch at low resonance and then reaches out and tweaks up
the Q pot. Turns out however that the resulting grunge is pretty cool after
all!

When I first fired up the prototype ASM-1 I had no level pots on the VCF
(it was a bunch of wires on the test bench) so the oscillators were going
full blast into the VCF. I heard it and it reminded me of an MS-20.

If you're going to run external signals into this VCF, I'd either build an
external mic pre-amp, or just lower the input resistors to something like
10K or 1K. The problem with the latter is that the input impedance may be
too low. Actually in the average studio it'll probably work fine for FX
work.

Hope this helps,

- Gene

----------
> From: Andrew Schrock <aschrock at cs.brandeis.edu>
> To: synth-diy at horus.sara.nl
> Subject: ASM-1 as an analog filter?
> Date: Tuesday, July 08, 1997 10:07 AM
> 
> All,
> 
> I am in need of an analog filter of some flavor, I was looking at the
> sherman filterbank as well as the waldorf x-pole and 4-pole, but they
were
> amazingly expensive for what you really got. (the 4-pole is at the
cheaper
> end of the spectrum, with the x-pole and filterbank being more expensive
> and duely more feature-laden) I simply can't afford $400-900 for a piece
> of processing equipment, no matter how amazing it may be. Which brings me
> to my question.. 
> 
> Could an ASM-1 board be modified to be a small filter? (by "small" I mean
> *physically* small, 1-2U's) I assume I could do this by omitting the
> VCO's completely, and making the entire synth less modular with the
> connections on the inside. (boo, hiss!) Not to worry, I'm planning on
> making a completely modular ASM-1 as well, I just want this to augment
> sampled and synthesized sounds that I already have. 
> 
> Moreover, has anybody *done* this yet? How does it sound? Can it be 
> overdriven for a more distorted sound? Ideally I would like to get very
> warped/distorted sounds out of the filter for electronic/industrial
music. 
> 
> Take care,
> Andrew
>