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Questions about tubes and gear that glows. FAQ

RE: 12au7 to 12bh7

Hmm, well, a 12BH7 draws 0.6A @ 6.3V for the heater, twice that of a 12AU7. Save for that, the other specs are close enough that it's almost a drop-in replacement altogether.

Looking up the amp and breezing through the manual, there are no mentions of transformer's heater winding specs, so it's tough to say.

There are four suggestions I can offer:
-Ask the manufacturer directly.
-Try to source out the part# and manufacturer of the power transformer. If you can get a datasheet, you'll likely find your answer.
-If you have the experience and don't mind voiding the warranty, you can measure the heater voltage before and after. If it drops below 6.3V with 12BH7s in the place of the 12AU7s. If it does, don't use them, and flip back to the 12AU7s.
-EDITED FOR POSTERITY (after Jim's correction): There may be a noticeable/measurable difference in the heat produced by the transformer.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively, warm, and long-lasting. Holy be thy heater.

Edits: 06/21/17

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