[sdiy] Through-zero FM - how much?

Ian Fritz ijfritz at comcast.net
Fri Oct 19 00:27:04 CEST 2018

> On Oct 18, 2018, at 11:54 AM, mskala at ansuz.sooke.bc.ca wrote:
>> On Thu, 18 Oct 2018, Ian Fritz wrote:
>> The only limits in using this approach are VCO and multiplier accuracy,
>> range and stability. Otherwise it is completely general.
>> Does this help?
> In your terminology, what I'm looking for is the range of A values allowed
> when initial frequency is 1, and it sounds like your recommendation is
> 0 to 1.
> -- 
> Matthew Skala
> mskala at ansuz.sooke.bc.ca                 People before tribes.
> http://ansuz.sooke.bc.ca/

Matthew —

I just fired up my analog unit and checked that A_max = 1.  Here’s what I did: 
1 Set Init to full up, no modulation
2 Set f_0 to 5 kHz
3 Set Init = 0
4 Modulate very slowly at A_max
5 Verified that output swing had delta_f of 5 kHz
So max of A is one.

My notes on the initial setup say I disconnected the expo current and adjusted the max linear current to go up to the max freq of the core.

If A_max were larger (say 2) then the delta_f would be 10 kHz, and then possibly the core could crash against its max freq if Init  > 0.

Even in my Reaktor TZ oscillator I found that A = 2 gave hash in certain regions.

So that’s why A only goes up to 1.


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