[sdiy] VCO Linear Voltage

[John Mahoney]

At 11:39 AM 11/17/2009, Ian Fritz wrote:
>At 08:00 AM 11/17/2009, John Mahoney wrote:
>>
>>Patching a VCO's sine output to a linear FM input yields 
>>interesting timbral changes. It needs to AC-coupled, though, or the 
>>pitch goes wild. At least, that's what they tell me. To be honest, 
>>I've tried it and the pitch has varied even when it's AC-coupled -- 
>>but I did like the timbral change.
>
>I recently looked at this question a bit for my new through-zero VCO.
>http://electro-music.com/forum/topic-29149-250.html
>
>The pitch shifts with AC coupling are quite small, even for large 
>modulation indices.  More importantly, I found that stable waveforms 
>can be obtained using just a touch of soft-sync to the master 
>oscillator.  The sync makes a slight change change in the spectrum, 
>but it eliminates the  small pitch shift entirely, and allows the 
>VCO to maintain the same waveform over a significant range of 
>frequencies.  This makes possible the use of digital-like results 
>such as from the original DX7, etc.
>
>The link above has sound clips and spectrograms so you can really 
>hear and see what we are talking about.
>
>Ian

Thanks, Ian, I remember some of that TZ-VCO discussion. However, I 
was talking about single VCO self-modulation, to which soft sync 
isn't applicable.

If I ever get all my backlogged projects built, I'd love to build 
some of your VCOs.

John