[sdiy] My 12 x Moog 921B VCO clones finaly built...

Jean-Pierre Desrochers jpdesroc at oricom.ca
Fri May 25 21:39:29 CEST 2012

>How many ppm/K ?
What I can tell is what I measured so far time/temperature wise.
The following are for each of the 12 VCO's I trimmed
right after their assembly:
I trimmed the 1v/oct trim pot for the best span on the VCO.
Then I carrefully adjusted the high freq compensation
with selected 50ppm resistors (around 1.6meg). Doing so
I've been able to reach a 7 octaves span within 1%.
I used a high precision tuner. I took some measures
in the evening (around 21degC in the basement)
then I unplugged the VCO for all night long.
Because I tuned all my VCO last winter the house temperature
is programmed to go at around 17degC by night from11:00pm to 6:00AM
and get back to 21degC.
So early in the morning at around 18degC  I plugged back my VCO and waited around 15min
for warmup. I hit the lower C key of my keyboard and the tuner showed
a nice C note at the center of the meter. I then checked the overall span
and it tracked nicely.
This is what happened for the 11 others.
Very stable VCO's !

 On Fri 25/05/12 16:14 , Ian Fritz ijfritz at comcast.net sent:
> At 12:24 PM 5/25/2012, Jean-Pierre Desrochers wrote:
> > > Could you be more specific? How many ppm/K
> ?>As stable as the MOTM-300 itself.
> >See modules specs:
> >http://www.synthtech.com/motm300.html
> Right.  Still no answer. :-)
> Ian 

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