[sdiy] Henry Walmsley's page

Kyle Stephens lightburnx at yahoo.com
Thu Dec 24 05:00:48 CET 2009

You got me there Paul ;)


-----Original Message-----
From: Paul Schreiber <synth1 at airmail.net>
Sent: Wednesday, December 23, 2009 7:50 PM
To: Kyle Stephens <lightburnx at yahoo.com>
Subject: Re: [sdiy] Henry Walmsley's page

Not all that interesting as a LFO.

Now THIS is:



Paul S.

----- Original Message ----- 
From: "Kyle Stephens" <lightburnx at yahoo.com>
To: "David G. Dixon" <dixon at interchange.ubc.ca>; "," 
<synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, December 23, 2009 9:45 PM
Subject: RE: [sdiy] Henry Walmsley's page

> David, it's basically an analog sequencer with the appropriate fixings to 
> run at audio frequencies (the VC "clock," tracking filter to 
> proportionately smooth out the steps), versus just spitting out CV. Least 
> that's how I'm reading it - those smarter than I, do you differ..?
> In any case, running it relatively 'slow' (closer tosequencer speeds) 
> would make for an interesting LFO...
> _Kyle
> -----Original Message-----
> From: David G. Dixon <dixon at interchange.ubc.ca>
> Sent: Wednesday, December 23, 2009 7:21 PM
> To: 'Ian Fritz' <ijfritz at comcast.net>
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Henry Walmsley's page
> Yes, Ian, I hadn't really thought about it (indeed, I spent all of about
> three minutes looking at the schematic), but it would be very difficult to
> get this VCO to track even above about 1.5 kHz.  I'd only just read
> something about V-F chips in H&H recently, but didn't really make the
> connection, as I have no prior experience with them.  .
> This thing is basically an analog wavetable oscillator, isn't it?  Is this
> similar to how DCOs are driven?
>> Since the VCO core is just used as a clock, it seems to me that it would
>> make *much* more sense to use a F-V chip (charge balance oscillator)
>> rather than a switched integrator.  I used the LM331 for my DoubleDeka
>> VCO, and it has phenomenal tracking up to well over 100kHz, and rock
>> steady temperature compensation using the Pease scheme.
>> For the OTA-based VCO it will be difficult to get the core frequency over
>> about 40kHz with decent tracking -- and even that will take qu

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