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In Reply to: RE: 4P1L in filament bias posted by andy evans on February 15, 2017 at 08:04:56
Yes, 4P1L is a great alternative, but isn't one tube per channel too little to drive a normal loudspeaker (Let's say a Audio Note AN-J for the sake of argument).
Follow Ups:
I use a pair, which is the equivalent to a 2a3, with a 70mA OPT. A single is equivalent to a 45. You can use three in parallel - just wire the filaments in series, then in parallel between the tubes. For 3 you really need a 100mA OPT.But if you want some volume at 50mA, you need a higher plate voltage. 4P1L is rated 250v a-k though you could probably push it a little.
Edits: 02/15/17
Apply Paul Joppa's 102 dB. rule to the claimed 93 dB. sensitivity and you get 8 W.
A look at a chart of 300B operating conditions
http://tdsl.duncanamps.com/dcigna/tubes/sheets/misc/4300b-2h.gif
suggests that 450 V. on the plate and -103 V. on the grid will work with your "iron". Don't expect lengthy service life under that sort of regime.
Eli D.
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