Are the 12B4 and 12b4A interchangable?

[musicman59]

I just bought a ModWright tube headphones amplifier (called Tryst). it has a pair of 6922 in the input stage and 4 12B4 in the output.
I have read that the best sounding 12B4 are GE but it seems almost impossible to find 12B4 tubes I can only find 12B4A.

Do you think the 12B4A can be used?

 

[rongon]

According to the data sheets, 12B4A is the version of 12B4 with a controlled heater warm-up characteristic. This was for using the tube in series heater chains.

12B4A -- http://www.mif.pg.gda.pl/homepages/frank/sheets/093/1/12B4A.pdf

 

[Tubelab_com]

Do you think the 12B4A can be used?

Yes, with very few exceptions the "A" version of a tube will always replace the plain version. You can not always go the other way.