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I would like to try running two different tube types, with different
voltages (AC) from the same transformer. The power tubes are 6.3V
and the input tubes are 2.8V.I can easily use dropping resistors to get the voltage down for the
2.8V tubes but I wonder what effect this will have on the sound.These are DHT tubes so...
Resistors in the filament string, good or bad?
I can go with a separate trans if necessary but this would be much
easier.Comments, anyone.
Follow Ups:
The resistor method works well save the heat generated. My approach now is to install some diodes and rectify the winding for DC.
Do you think you have enough current capacity on that particular secondary transformer section to install a simple bridge and filter capacitor to generate 2.8VDC? Maybe you can also install a light bulb in series with the input tube filaments to create a voltage divider? But then there are the issues with polluting the AC 6.3V with rectifier noise maybe, etc.
As said, run the output tube AC and rectify the 6.3v for the driver DHT, giving you about 10vDC which you can then turn into a current source using a Ronan Reg type design. If it's 2.8v it sounds like a double triode, and if it has the alternative of running at 1.4v you may find that's easier to achieve with a current source.I tend to double up where I can - e.g. if I have a 12v heater winding I rectify that for a -15vDC supply to the CCS.
come up with.Yes Andy the input tube is a double triode the 3A5, cute little
tube I just gotta try it.By the way do you know where I can find a schematic for the ronan
reg? I googled and searched the archives and came up empty.
Cal - mailed you details. Andy
I will give this a try, it looks interesting.I truly appreciate your help.
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