SV: Re: [sdiy] Thomas Henry XR-2206 VCO Page Up

[karl dalen]

The reason for the lack of low range might be R5,
it causes an offset  to the freq of the XR2206 VCO!

I suggest removing it and adjust Iref in the expo a bit
and also as Rene mentioned use a larger cap if needed.

KD

--- Scott Stites <scottnoanh at peoplepc.com> skrev:

> Thanks, Ian!  
> 
> Yes, that lower octave was the heartbreaker.  Tuning for perfect flatness
> down that low would shift things enough on the high end where the tracking
> just wasn't terribly good beyond five octaves.
> 
> I guess the main reason one would want to worry about the low end like that
> is that the ramp wave (from the skew) is double the frequency, so with the
> wave skewed to the octave up, it would still have the same amount of error.
> 
> Of course I think it's possible to get a ramp wave at the fundamental
> frequency, but that takes a bit more circuitry than Tom was willing to put
> in.  
> 
> Cheers,
> Scott
> 
> 
> -----Original Message-----
> >From: Ian Fritz <ijfritz at comcast.net>
> >Sent: Jun 29, 2006 11:40 AM
> >To: Scott Stites <scottnoanh at peoplepc.com>, SDIY
> <synth-diy at dropmix.xs4all.nl>
> >Subject: Re: [sdiy] Thomas Henry XR-2206 VCO Page Up
> >
> >At 10:02 AM 6/29/2006, Scott Stites wrote:
> >
> >>We were able to get around 5 musically useful octaves out of it - it would 
> >>be much better if the low end would have cooperated more, but we think 
> >>that's all the XR-2206 would provide without running afoul of the law of 
> >>diminishing returns - IE, it would start to increase in parts 
> >>count/circuit complexity, which Thomas reasoned would defeat the original 
> >>intent of the circuit (a very simple, easy to build VCO with some neat 
> >>features).
> >
> >
> >Hmmm... looks better than 5 octaves to me.  Within 0.1% from 1V to 8V.  I'd 
> >call it 7 octaves.
> >
> >Nice work!
> >
> >   Ian 
> >
> 
> 
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