[sdiy] Re:

[Ray Wilson]

Hi Milo

The model car racing transformer may be part of the problem. Typically these
are half wave rectifed outputs which are VERY noisey and need to be filtered
with 10s of thousands of uFs of capacitance. Even if it is full wave
rectified you will still need 10s of thousands of uF to smooth it to an
acceptable level. I would start with a good power supply design.

Here is a simple one.
http://atlas.csd.net/~rjwsoft/ninevoltsupply.html

Here is a more complex but better one.
http://atlas.csd.net/~rjwsoft/powersupply.html

Ray

  -----Original Message-----
  From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of
dreichert at sympatico.ca
  Sent: Tuesday, October 14, 2003 4:53 PM
  To: Milo Barrowclough; synth-diy at dropmix.xs4all.nl
  Subject: [sdiy] Re:


  hello everybody

  I love electronic sound and i am well into all kinds of synthesizers.
Recently i have been trying to build my own rudimentary synth. I have made a
simple 555 oscillator that works great. Since the then i have been trying
more advanced circuits involving op-amps, but without success. I have tried
to make r.a. penfold's vco, penfold's filter, and a basic lm3900 VCO.
Whenever i try any of these circuits , it either emits nothing or a quiet
buzzing noise. I am almost certain that my circuit is correctly built, i've
checked the bastard about 50 times. Can anyone help me? I think that the
problem may be the power supply, i am using an old scalextric (model car
racing) transformer that puts out 12 volts. Is this a common problem with
op-amps? Whats going on?
  Thanks very much
  Milo


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