ENS-76 VCO Option 2 question

Bob Zimmer bzimmer at voicenet.com
Tue Mar 25 18:38:49 CET 1997

At 09:20 PM 3/24/97 -0800, you wrote:
>There's a really nice triangle to sine converter in Jung's Op Amp
>Cookbook.  It's used in Thomas Henry's Deluxe VCO, which I've built a pair
>of.  It's based around a pair of transistors and a diff. amp.  Gives an
>even cleaner sine wave than the thru-zero VCO in EN 129.
>BTW, did you have any problems with the srm/pwm circuit?  I noticed that
>if I turn the PW pot a little too far in one direction, the pulse wave
>will just stop, while the saw wave keeps going.  My only guess is that
>it's because I added an input scaling circuit for PWM.  Also, I notice
>that my saw waves don't look totally clean.  There's a little bit of a
>jaggy in the middle of the slope.

I have noticed that the Pulse Width pot (+15V on one end, Gnd on the other)
swings the pulse output from +5 VDC flatline to a -5 VDC flatline with a not
too bad pulse in between.  I have also noticed that the Pulse seems to shift
voltage out as well.  Being 0 to +10V at one end and +-5V at the other.  I'm
going to try to add a couple resistors to control the swing.

The Sawtooth output is really wierd as it seems to break in half and double
the frequency!  There is also a small glitch at the point where it breaks (0V).

Both waveforms seem to sound interesting though and I'm going to keep them,
but I'm going to try to add an extra 'more normal' sawtooth converter to the

  >=== Bob Zimmer -- Philadelphia PA ===<
  >=== bzimmer at voicenet.com          ===<

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