[sdiy] hammond imitation

Tue Nov 5 00:23:57 CET 2002

I'm with Harry - I would propose that it's a slight doppler thing due to
Leslie horn/drum movement. I just can't see magnetic loading causing enough
of a drag on the tonewheel system to cause a pitch shift. The run motor is
sync'ed to the line frequency, so there is some mechanism which will tend to
speed it up if it falls behind (rather than being a free-running system).
Also all of the sub-shafts have some built-in slip so that you can
physically stop one of the wheels without affecting the rest of the
generator.

Try a chorus box too - the grungier the better. An old E/H Clone Theory is
really gross and sounds great. But of course the best effect is a real
Leslie. The older ones (like the 21H) have only about 20 watts of power so
if you max out the volume pedal the sound is very grumbly and growly. Pitch
bending by playing with the motor controls is a bit of a problem on the big
Hammonds (A/B/C/BV/CV/B2/B3/C2/C3) because the run motor will stall out if
it loses track of the line frequency. The non-M spinets (like the L and T
series) have a single motor so you can shut it off and on and get the wild
pitch bend effects. The problem with this is that it will shut off the tubes
also, so you should bypass the AC power to the amps so you can do motor
stuff.

Ooops getting off track - I love to talk about Hammonds...

- Gene

(who coincidently fired up the old beat up hammond in the garage over the
weekend and rattled the garage door)

-----Original Message-----
From: harrybissell at prodigy.net [mailto:harrybissell at prodigy.net]
Sent: Monday, November 04, 2002 1:20 PM
To: jhaible at debitel.net; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] hammond imitation

The hammond key contacts are not arranged to close simulaneously...
they close in a harmonic order like 8' then some mix then 4'

or something like that. I know they don't close together, but don't know the
order...

This can give some odd effects when the keys are pressed fast or slow...
almost a variable attack. tease the keyboard with a real
slow press and see what happens...

Some people play with the motor controls to get odd modulation /
pitchbend... but NOT what you're talking about...

could you be hearing the normal Leslie speaker at chorale speed...
Most hammonds are so equipped (and I'd never turn it off ;^)

H^) harry

>Hi,
>recently I have run my CX-3 organ thru my Storm Tide Flanger and I used the
>Envelope Follower modulation of delay time to get some "outer space"
>sounds.
>Now with this setup still intact and the Flanger accidentially left in the
signal
>path, I tried to play an "ordinary" hammond sound. Noticed the Flanger
immediately,
>and switched it off.
>And then switched it on again.
>I found that a _tiny_ bit of envelope follower to modulate the delay time
(und thus
>to modulate frequency) was very pleasant _and_ I even think it makes the
Hammond
>sound more realistic.
>I wonder if this is really true (I have also changed the frequency response
with that
>flanger, obviously, so the FM effect might not be the important part
really), and
>if it is true, then _why_?
>Is there a mechanisms on a real tonewheel organ that will slightly modulate
the
>frequency when keys are depressed ??
>I really don't think so, but if I make some wild speculations, I could come
up with
>an idea to explain this. (I mean this phenomenon of which I'm not even sure
>that it exists. (;->) )
>Here we go: 
>The tone wheels are operating with an electromagnetic pickup. If this
pickup
>is connected to the electronics by pressing a key, it is _loaded_. This
load
>will draw some energy from the mechanical system.
>Now the big question is: Is the electrical load heavy enough? And is the 
>propulsion for the tonewheels "soft" enough to cause any perceivable
>effect on momentary frequency??
>I really don't know enough about hammonds to answer these questions,
>and my guess for an answer would be "probably no". But then again
>I heard the mixing of drawbars is done with resistive wire (?) and a
>transformer, so I guess it's not all high-impedance stuff without much
>power consumption, is it?
>Any comments welcome,
>JH.