[sdiy] MS-20 Filter Clone Queries

[Kyle Stephens]

I'm building an MS-20 filter clone, as seen here:

http://electro-music.com/forum/phpbb-files/ms20_13700version_142.gif

In regards to the cuttoff CV expo converter, I haven't any matched PNPs lying around but I do have a few LM394s (matched NPNs) I got cheap from Futurelec. There's some simple rearranging I can do to make the NPNs work, right? I've seen dual matched NPN expo converters elsewhere, but I'm not sure how to apply them to this instance...

Also, this schem says it runs on +/-12V, while I'd been planing on a +/-15V standard for my system. In general, is current consumption the main issue for running at 12V? What needs to be changed if I want to run the filter at 15V?

As a somewhat open ended side question, are there any other possibilities and potential problems within the design?

I've been looking at every execution of the MS-20 filter I can find, from the original schematic (Tim Stinchcombe's analysis thereof has been most helpful) to Rene Schmitz's (which this version is based on - cheers to the good work there!) to the Doepfer version (the A-106), looking for mods and design considerations and pitfalls.

I like the Doepfer's resonance loop send among other things in that manifestation (http://www.doepfer.de/A106.htm), and want to try out various combinations for the res diode clippers with selector switches, like different, colored LEDs, Si and Ge diodes, FETs wired as diodes (I got the idea from fuzzbox techniques).

Can you drive the filter's input without blowing anything up, and if so, how..?

Sorry for the flurry of questions!


_Kyle