SIL components, and Re: Thru zero FM

[Magnus Danielson]

From: Martin Czech <martin.czech at intermetall.de>
Subject: Re: SIL components, and Re: Thru zero FM
Date: Thu, 30 Sep 1999 13:51:57 +0200 (MET DST)

> 
> :::>I wonder how good the time-dependant modulation works with other >TZVCOs
> :::>like the E.N. one. Thats another way of asking if Yamaha style FM is
> :::>possible in the analog realm.
> 
> click, rrrrrrrr (automatic endless tape starting),
> hisssssss, scratch, an automatic voice says: 
> 
> Yamaha synths do phase modulation, not FM.
> This can be proved very simply:
> 
> Modulate one OP with a second, so that a very fast vibrato is audible.
> Now tune down the modulator frequency, viola, the frequency modulation  becomes
> inaudible. This tells us that the frequency shift depends on modulator
> frequency, this is a clear hint that phase modulation is applied.
> One c ould also simply look into Yamaha publications, the formulas
> also show phase modulation, but this is boring.
> 
> Are there other audible differences?
> 
> Yes, PM ensures equal sideband amount for any modulator ratio, whereas
> FM does not (decreasing with ratio). Therefore PM usually sounds brighter.
> 
> If only sine waves are used (this means NO STACKED modulators), and only one
> ratio, then PM can be tuned so that it gives exactly the same signal like FM.

BTW. Do someone know how Yamaha implements their frequency generators?

I mean, do they use phase-accumulator techniques or do they use IIRish
generators?

I would guess for phase-accumulators since they lend themselfs to PM by
simply adding the modulation signal to the output of the phase accumulator
prior to the waveform generation.

Reading the patent migth shed some ligth (what was the P/N number now again?).
Anyone to pop the the top plastic of a Yamaha chip and reverse engineer their
chip?

Cheers,
Magnus