[sdiy] What to do with XC4003A's

[Magnus Danielson]

From: patchell <patchell at silcom.com>
Subject: Re: [sdiy] What to do with XC4003A's
Date: Sat, 09 Jun 2001 12:37:31 -0700

> 
> 
> Magnus Danielson wrote:
> 
> >
> > Yeah... if you do the phase accumulator you got the frequency
> > divisions for free. Toss it through waveshaping and spurt out tones
> > and you could even build yourself a Hammond organ equalent... ;O)
> >
> > Cheers,
> > Magnus
> 
>     Now, this is a subject I am pretty ignorant on (Hammond organ tone
> generators).  I guess I have no excuse for being ignorant on this subject
> (My father repairs old Hammond organs as a quasi hobby/business), but I am.
> Are there any good descriptions on the internet that explain the operation
> of a Hammond tone generator/organ.  Did they all use drawbars?

To the best of my knowledge, yes...

I was able to easilly track down a Hammond service manual on the web
with schematics. It gives a fairly good insight into the operations.

Actually, a Hammond is nothing but the electromechanical equalent of
an top-octave and divide down setup. The thing is that you key the
signal addition from the electromechanical sine generators onto 9 bars
and these are then levelcontroled by the drawbars to form the mixing
and then amplification. You could easilly do something equalent I
thought. You don't have to be restricted in your choice of waveforms
thought.

Some parts of a Hammond organ is really a hillerious way of solving
problems... I read the schematics for fun and learn interesting
things. Like the electromechanical pitch-shifter! One day I will
attempt to do one in solid state!

Cheers,
Magnus