[HAM] why are tonewheels superior?

[Kon Zissis]

Hi David and everyone.
In my curiosity to educate myself  about the  sound of  different  TG
calibration curves  , I once  recalibrated  the whole TG of my 1962 C3
to produce very high output levels  in  order to improve the signal to
noise ratio but unfortunately this very ''hot'' TG output curve sounded
very bad because  the waveforms had become noticeably less pure  and
more dirty sounding and more warbly  because the pickup rods were closer
to the tone wheels than they should be for the optimum waveform
tonality.  My C3 ended up sounding  more ''electronic'' due to the
dirtier  waveforms so I subsequently recalibrated the TG back to a stock
TG output curve. 
 
Last year I again experimented with a louder  than normal TG output
curve and so I  recalibrated the whole TG  to be around 10 millivolts
peak to peak  louder than normal . This is  more or less the limit
before the waveforms start to  lose their purity  and start to sound bad
. 
 
Dominik ter Meer had recalibrated the whole TG of his recapped 1962
A-100 to produce a fatter than stock sound  and he was very pleased with
the improved sound . Dominik's TG output curve  has a slightly louder
bass and midrange output curve more like that  of the pre 1956 Hammonds.
 
 I decided  to use Dominik ter Meer's  recalibrated TG curve of his 1962
A100 as the basis for my own  new TG recalibration  but I wanted a
better signal to noise ratio because I use bass boost and overdrive  and
this emphasises some of the residual TG hum  especially on the upper
octaves of the manuals with the normal TG output curve and I wanted to
remove this hum. 
 After experimenting ,  I realised that I should not increase the TG
output levels  any more than  10 millivolts  peak to peak  above the
normal stock levels and  this time  my recalibrated  louder  and fatter
than stock TG output curve sounds quite good because the TG  waveforms
still sound normal  but the signal to noise ratio has improved. As well
as this , because of the louder TG output curve I have replaced the v4
12AX7  valve in the AO28 preamp with a 12AX7  valve which has less gain
and thus the  normal fluttering hum and  noise coming from the vibrato
scanner  has also noticeably reduced. 
 
I have built a 12AX7  based EQ / overdrive  unit in my 1962 C3 and I
have built a similar unit in my friend's  recapped 1959 C3  which has a
stock TG output curve  and when I set the bass boost and the overdrive
controls in  my 1962 C3 to the same  settings as that of my friend's
1959 C3  , my friend's  1959 C3 has  more TG induced hum noise when
playing on the upper octaves of the manuals.
 
As to some reasons why the tone wheels sound better , the  tone wheel
waveform itself is extremely important and other factors such as leakage
and crosstalk and some undertone  under the main waveform  help to
create the distinctive  Hammond sound.   Other factors are the loading
and the interaction of the low impedances  of the TG pickups  when
playing chords and  with multiple drawbar settings  where  the TG notes
are borrowed  by the various drawbars .
 If the TG pickups had high impedances there would  be a different
loading effect  and this would become audible when playing chords and
when using  multiple drawbar settings.  
The nine contact mechanical key switching  interacts with the  low
impedance  TG pickups to create the nice sounding key click effect. 
Organs that use electronic  or gated key switching  do not have this
natural sounding  key click effect but instead they can produce more of
a ''thump'' noise  which can sound  unpleasant especially when using a
bass boost and an overdrive  effect. 
All the best.
 Kon
 
David Anderson wrote:
What I *have* noticed is that, due to the original calibration  
process of setting the final output by magnet position, not all the  
waveforms are precisely the same because you have two distances  
involved: the difference between the peaks and valleys on the  
tonewheel and the distance between the tonewheel and the pickup. When  
you move the magnet, you change the ratio of those differences.  
Result: different waveform.