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Re: referencing heater supply ground to B+

Hi
When you say "the heater supply ground is reference to B+." are you talking about DC supplies?

If they're AC - the only thing I know anything at all about - then I think the voltage you're talking about is not a reference but a bias voltage and is not chosen as a percentage of B+.
In IDHT's there can be a diode in effect between the heater and the cathode through which noise can get into the audio signal. The purpose of the voltage applied (by means of a divider from B+) is to bias the filament positive relative to the cathode, at a steady DC voltage just high enough above the cathode's potential to saturate the diode (using up all it's current swing potential), making it immune to influence from the heater' AC swing. It doesn't have to be that high - for six and twelve volt heaters people seem to use anything from 20 to 50 VDC, depending on the tube and the situation. That's pretty much all I know. Do a search of all forums on filament or heater bias with Paul Joppa as the author, there are a few fairly extensive explanations of his posted somewhere.

HTH



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  • Re: referencing heater supply ground to B+ - Ian L 20:20:54 03/12/07 (0)


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