OTL Asylum

OTL, Output Transformerless Amplifier User Group.

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RE: I've read that the 12B4A is amazing

Posted by Lew on February 15, 2016 at 11:16:48:
I don't off hand know the specs of the 12B4, but I think it was used as a driver tube in some of the revered Marantz amplifiers, 8B and/or 9. It also may be used in early HK Citation tube amplifiers. This suggests it has a relatively low output impedance when used as a driver, which is also good for an OTL. Believe me, JF was a pragmatist. If he used the tube early on, it's because he could get them, and notice that he paralleled ten of them to get something like 10 or 30W (I forget which). Later, when because of TV the power beam tubes like 6LF6 came around, he switched to them probably because more bang (power) for the buck.