• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube filaments in series?

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Dear tube-lover,

Is it detrimental for tubes of same type and make to wire their heaters in series (e.g. to suit two 6.3V tubes with a 12.5 supply)? I know some tubes have a certain affix indicating their suitability for heaters connected in series, what about your average tube?

Cheers --- Simon
 
Some of the odd-voltage variants of common tubes have controlled heater warm up characterisitcs (usually around 11 secs) specially made for series wiring.

You can sometimes get 3V filament versions for a song and series heat them from a regular 6.3V tap.

pm
 
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