[HAM] DC filtering to the heater filament voltage of the AO28

[Kon Zissis]

Hi David.
Thank you for your reply.
>With lower heater voltages....This  
>will mean lower maximum output from the preamp before distortion;  
 
There was some slight distortion when playing the organ at full volume
before I replaced the power supply filter capacitors and the power
supply resistors , the plate ( anode ) resistors , the screen grid
resistors and the cathode resistors and the cathode bypass capacitors ,
and now there is still some slight distortion when playing  the organ at
full volume but the hum level has been reduced and I think that the AO28
seems to sounds better now 
 
>My concern was not with the tubes, but rather with the power  
>transformer's filament winding. When you run tubes on DC filaments,  
>you usually need a filament transformer with a higher wattage rating.  
 
This indicates that it is better for me to remove the bridge rectifier
because it adds more current draw strain to the filament winding of the
power transformer. The AO28 transformer in my own 1962 C3 and in my 1965
C3 and also in a 1960 RT3 that was previously in a church,  gets quite
warm under normal operation so therefore this indicates that it is being
run at near the maximum limits in the stock AO28 wiring configuration. 
 
I am going to add an extra 12AX7 in my 1965 C3 as part of my 12AX7 based
EQ / Overdrive unit that I will build for the C3  so therefore this
extra 12AX7  will draw more current from the filament winding thus also
suggesting that I should remove the bridge rectifier and go back to the
stock AC filament voltage wiring. 
 
To help minimise  the added current draw  because of the extra 12AX7
valve , I will remove the pilot lamp and I might possibly replace the V6
6C4 valve with a IN4007  silicon diode. Some time ago there was a
Hamtech discussion about replacing the V6 6C4 valve with a diode and I
tried this out and there was no  noticeable difference to the percussion
sound so therefore this looks like a worth wile modification. 
 
To replace the V6  6C4 valve with a IN4007 , you simply connect the
cathode of the diode to pin 7 and the anode of the diode to pins 1 and
5. 
All the best.
Kon