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222.166.2.28
Just wondering how important it is to have the voltage for the heater being elevated ?
Any simple method to provide an elevated voltage for the heater supply ?
(I am generally refer to 12au7, 6dj8, 12ax7 ...etc).
TIA
Alan
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implement whenever I can/have the time.
iBasso DX100,DX50. HiFiman 901 balanced. AK100 modified. fi.Q amp, RSA Intruder, The Lightning, Fostex TH900 balanced, JH13 Pro balanced. etc.
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"Just wondering how important it is to have the voltage for the heater being elevated ?"
It depends on the circuit. Sometimes you have to float the heaters to keep from exceeding the cathode to heater voltage rating of the tube, sometimes you float the heater to keep the heater noise out of the audio.
"Any simple method to provide an elevated voltage for the heater supply ?"
Just make a voltage divider, two resistors in series from the B+ to ground.
The value of the resistors will determine how much current the divider will draw and the voltage at the intersection.
Connect the "ground" point of your heater supply at the intersection of the two resistors instead of ground. Placing a cap to ground at that point is probably a good thing. 20uf should work fine.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
TIA
Alan
With a voltage divider off the B+ supply.Connect the heater winding center tap (or the resistor created center tap or one side of the heater winding) to the voltage divider instead of ground.
In other words, whatever point in the heater circuit that is grounded now, connect to the voltage divider instead.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/26/14
That is very important if you experience hum in high gain stages of the preamp or phono stage and what many people do is just find a convenient source that exists inside the preamp and then twist a pair of 100k or 220k resistors together and than hook them to the source and then across the filaments.
Honest amplification is better than excessive 2nd order distortion anytime.
I am not quite sure what you are hoping to accomplish by 'elevating' the heater/filament voltage-
If the voltage is elevated too much(more than ~5%?) it will shorten the life of the element/tube....
Happy listening
…not increase the voltage difference between the two ends of each filament. Likewise, I think by "across" Mike Samra means you connect one resistor from each side of the filament circuit to a DC voltage, to create a virtual center tap. If the filaments are referenced directly to ground, the maximum cathode to filament voltage rating might be exceeded in some circuits, so you raise the filament average potential to some higher DC value, closer to where the tube cathodes are running. This can arise e.g. if you have a cathode follower, where the cathode may ride at a couple of hundred volts DC.
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