[sdiy] ASM1 VCO single sided PCB design tests OK

[Magnus Danielson]

From: charlie lamm <charlie at charlielamm.com>
Subject: Re: [sdiy] ASM1 VCO single sided PCB design tests OK
Date: Fri, 18 Apr 2003 21:04:26 -0700 (PDT)

> >
> > "You will need matched PNP for Q1" it should naturally say NPN!
> 
> Ooops, my bad.  Dumb mistake ("no points in"--I need to keep telling
> myself this!)   I have corrected this typo.  Glad you are paying
> attention!!

It's always nice to check out what others have observed. It may be that they got
something wrong or mentions some neat little trick or observation, like the
polarity reversal of the earth magnetism or some other minor effect.

> > As for power-supply, the actual VCO core doesn't care frequency-wise about
> > which voltage there is, but the CV-input side will. If you have a frequency
> > pot reaching for -15 V (which it usually is) then you will have dependencies
> > right there. A +15V to GND pot will however probably be safe (recall, it is
> > years since I did the actual calculations myself).
> >
> 
> The point I'm trying to make is that the P supply feeding the op amps has
> to be "stable DC". If one rail waivers in voltage relative to ground and
> the other stays put, the oscillator seems to go out of scale.  Or did I
> evaluate what I was seeing on the bench wrong?

Well, the VCO core depends on the +15V to GND potential differance. AC signals
there WILL however not only make it to the output but also cause modulation of
the waveform. 

> Maybe it's more accurate/clear to say the circuit needs a well regulated
> supply and just leave it at that?

I concurr. Better just say it needs stable supply.

Cheers,
Magnus