[HAM] Final A/B test results for the DC filtering to the heater filament voltage of the AO28

[Kon Zissis]

Hi everyone.
I have just done an A/B test with the stock AC filament voltage wiring
set up and then with the Schottky diode  bridge rectifier with  the
10000 uf smoothing capacitor DC filtering set up . 
 
With the TG switched off , and the AO28 preamp and the Leslie 122 set at
full volume, I switched the wires between the stock AC  filament voltage
set up and then the  DC filtering set up and there was no difference in
the level of hum !!!
 
There is the normal subtle and  non bothersome background hum and this
is more or less the same regardless  of whether the stock AC voltage or
the filtered DC voltage is sent to the heater  filament wires.
 
Finally after all these years, it is now my turn to say 'IF IT AINT
BROKE, DONT FIX IT!!!!!'.  Ha ha :-).
 
Because I have verified that  there is no real need  to add the DC
filtering to the heater filaments of my AO28, I am now going  to finish
with this DC filtering experiment  and rewire the filament voltage back
to the stock AC voltage set up.  
 
I would imagine that the Hammond engineers would have experimented with
this set up and then come to the conclusion that using the AC filament
winding with the grounded  centre tap is OK to minimise the hum.
 
Of course one thing that may need to be taken into consideration is  the
possibility that  the electricity supply in different countries might
contain more "dirt" or a higher line frequency  than the Australian  240
volts 50 Hz electricity  supply so therefore it might be possible that
in those countries  this "dirt" or the higher line frequency might cause
excessive hum  problems that require DC filtering for the heater
filaments. 
Experienced techs and hobbyists who are on this list  might be able to
verify if this is correct. 
 
All the best.
Kon