Path: utzoo!attcan!uunet!decwrl!asylum!osc!jgk
From: jgk@osc.COM (Joe Keane)
Newsgroups: sci.electronics
Subject: Re: Along the heterodyne lines, what about "FM" synthesis?
Keywords: FM synthesis, modulation
Message-ID: <3802@osc.COM>
Date: 13 Sep 90 09:46:59 GMT
References: <1040@beguine.UUCP>
Reply-To: jgk@osc.COM (Joe Keane)
Organization: Versant Object Technology, Menlo Park, CA
Lines: 21

In article <1040@beguine.UUCP> Jeff.Miller@samba.acs.unc.edu (BBS Account)
writes:
>Comming from more of an EE background, explanations of FM synthesis
>such as used in the Yamaha DX-7 (mostly by musicians) leave me
>confused. I suspect that what Yamaha passes off as "FM" synthesis
>would be far better described as AM synthesis. 

It really is frequency modulation.  If you put in a certain control voltage,
the oscillator has a certain frequency.  If you put in a higher control
voltage, the oscillator has a higher frequency.  This is nothing new if the
control voltage is derived from a static source such as the keyboard.  I think
the supposed innovation is that you can use other sources to dynamically
modify the frequency, even changing the phase within a single cycle.

>And while we're at it, isn't a ring modulator just a VCA? Or a special
>case of a VCA with a square wave as one of the inputs? Isn't this the
>same as a chopper?

Yes, a VCA and any modulator do the same thing, which is multiply two signals
together.  I'm not sure about the square wave part, but i do know a ring
modulator is basically a multiplier.