Do NOT use MPF-102 in the ASM-1!

[Christopher_List at Sonymusic.Com]

  >>   After building a VCO, I was having a problem with the output level
  of the
  >>   sawtooth and didn't think it had anything to do with the FET. I mean
  it
  >>   was working and tracking and making sawtooth waves. I put it down
  for a
  >>   few days, came back and tried it and it wasn't working at all.
  Testing

  > I had a similar experience with the 2N4391's that I am using.
  >
  > Did your 3140 "hang" at +15V?

  Yes - but only after it stopped working. Before then it was working, but
  the sawtooth was between +5 and +2.5.
  Weird.
  It <<was>> working properly - with the wrong levels. Then, all of a
  sudden, it wasn't.

  > Mine did and the LM311 kept ticking at HF (some 100 kHz to 500 kHz...)...

  I didn't notice this after it died.


  > I hooked an 30 pF cap from the input to ground...
  > this slowed things down and allowed the FET to have
  > time enougth to empty to cap... can something similar maybe work for
  the MPF-102's?

  I replaced the MPF-102 with an NTE466. It was still broken.
  Next I replaced the 3140. It worked. I don't know what the MPF-102 was
  doing, but it worked for a little bit, then fried my 3140 - so I'm
  staying away from them!

  One more tip regarding the VCO - You can wave shape the sawtooth into a
  triangle, and you can waveshape that into a sinewave, without too many
  components. Sawtooth -> triangle is done by full wave rectifying, then
  doubling the amplitude and level shifting it. Tri->Sine is done by
  running it through a properly configured CA3080 - I think the CA3080 data
  sheet has details...

  - CList