[HAM] Bill Fox's modified L-100 was Wax caps measured and then placed in four pans...

[Kon Zissis]

Bill Fox wrote:
Hi There
All this calibration wonder! I have taken a L100 and done some of "
Frederick Somervilles' " circuit mods, with great success...
 Took a basic digital volt meter and measured directly off the tone
termnial
strip. Adusted all tone outputs to 2.8 volts across the board, by moving
the
magnets. This L100 has lots of key click, hot B3 percussion and just
screams
thru my Leslie 147!!! Also insalled a killer left hand bass cicuit. Just
wanted to share my results.
 
 
Hi Bill . 
When you wrote ''2.8 volts'' did you in fact mean '2.2 millivolts RMS  (
mV RMS ) ?   
 If so this means that  the output levels for the TG notes 18 to 91 are
7.92 millivolts peak to peak  ( mVpp )   because  2.8 mV RMS  multiplied
by 2.828 =  7.92 mVpp.    
Because of the lack of manual tapering  in the spinet organs  the
factory stock  upwardly rising  output curve of the upper midrange and
treble region of the TG notes  help to cause the spinets to sound
thinner than the  console organs  with the manual tapering  so therefore
the recalibrated straightened out   output curve  would indeed produce a
warmer or fatter overall sound  as I found out after modifying and
recalibrating a friend's 1970 T-300.
 
I was at my friend's house and he put  the Jimmy Smith album ''Damn'' on
the CD  player and I was playing the T-300 along with the album and even
though the T-300 was  heard through it's own built in Leslie drum , the
organ  sound with the 888000000  drawbar setting and the third harmonic
percussion was quite nice and fat , sounding  similar to Jimmy Smith's
organ on the ''Damn'' album. 
 Before I recalibrated the TG and modified the preamp , this  T-300
originally  had a terrible thin nasal sound especially  on the top
octave of the manuals with the 888000000 and 888800000 drawbar settings
which sounded quite thin and useless.
 
A  useful modification to fatten up the sound of the L-100 is to
completely remove  the R203  4.7 mega ohms resistor  from the V1 12AX7
input valve. I  tried this out on my own 1963 L-102 and the resulting
fatter sound is quite pleasing. 
You can also create a variable treble boost control by wiring up a 2
mega ohms potentiometer  as a rheostat  in series with the C203  39 pico
farad feedback capacitor which is wired on the V1 12AX7 input valve.
All the best.
Kon