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Re: BATTERY for filament heating

Since one can get more than 12V with a 12V lead acid battery then maybe the 2A3 and the 845 filaments can be connected in series. To maintain 3.25A through the battery a resistor of 2.5/0.75 = 3.333R, >2W could be used in parallel with the 2A3 fil.

That is if we can make sure the battery provides constantly 12.5V across it (or 3.25A through it). I think that some 12V batteries can go up to 13-14V when fully charged. So some adaptive solution is needed i.e. regulators or maybe a trimpot and a meter.

Seems complicated and if cathode bias is used it gets worse defeating my original purpose of avoiding resistors in the cathode.
But if using RC coupling and fixed bias then it seems worthwhile.

If I do use batteries in the end I think I'll go for either one of two options:

a) work out the max time I'll be likely to be listening to music and get an appropriate battery

b) have two batteries which can be connected alternately and have enough capacity so that one can keep playing for as long as the other takes to get charged. The problem would be how to make the transition.


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  • Re: BATTERY for filament heating - stelios 08:45:46 10/27/01 (0)


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