[sdiy] Fwd: FM math question

[Magnus Danielson]

> At 06:31 PM 10/15/2008, Gerald Stevens wrote:
>>I'm glad that you're thinking about these details Ian.  It's my
>>understanding that a thru zero FM oscillator is desirable because it can
>>produce the same harmonic series as the digital algorithm in a DX
>> operator.
>
> Sorry, but I have to stop you right there.   :-)
>
> It's desirable because of the many fantastic sounds it can make.  If you
> want a DX, then get a DX.
>
>
>>  Now, since the DX7 only uses sin wave oscillators and modulators, I was
>> wondering whether or not your saw-tooth version negates the "benefits"
>> of
>> thru-zero frequency modulation.
>
> But this is what we were just talking about!  With a Sin shaper at the
> output it seems very similar to Sin wave FM.  Probably actually the
> same.  Have you listened to the demos?  Most folks so far like them.

A curious point is that a saw phase-modulated to 2*pi*k radians will
frequency shift (SSB) the carrier by k*fm when k is integer. For
non-integer k values the peak will be shifted, but with side-bands...

Cheers,
Magnus