<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1170" name=GENERATOR></HEAD>
<BODY>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2>Hi
Milo</FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2>Here
is a simple one.</FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2><A
href="http://atlas.csd.net/~rjwsoft/ninevoltsupply.html">http://atlas.csd.net/~rjwsoft/ninevoltsupply.html</A></FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2>Here
is a more complex but better one.</FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff size=2><A
href="http://atlas.csd.net/~rjwsoft/powersupply.html">http://atlas.csd.net/~rjwsoft/powersupply.html</A></FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2>Ray</FONT></SPAN></DIV>
<DIV><SPAN class=046310900-15102003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B>
owner-synth-diy@dropmix.xs4all.nl
[mailto:owner-synth-diy@dropmix.xs4all.nl]<B>On Behalf Of
</B>dreichert@sympatico.ca<BR><B>Sent:</B> Tuesday, October 14, 2003 4:53
PM<BR><B>To:</B> Milo Barrowclough;
synth-diy@dropmix.xs4all.nl<BR><B>Subject:</B> [sdiy] Re:
<BR><BR></FONT></DIV>
<DIV>hello everybody</DIV>
<DIV> </DIV>
<DIV>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? </DIV>
<DIV>Thanks very much</DIV>
<DIV>Milo</DIV>
<P>
<HR SIZE=1>
<FONT face=Arial size=2>Want to chat instantly with your online friends??<A
href="http://uk.rd.yahoo.com/mail/tagline_messenger/*http://uk.messenger.yahoo.com/"><B>Get
the FREE Yahoo! Messenger</B></A></FONT> </BLOCKQUOTE></BODY></HTML>