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07/23/14 at 00:53:38


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RE:  ZenSE84B Humm and Input Tube Bias (Read 792 times)
johndoe
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RE:  ZenSE84B Humm and Input Tube Bias
07/03/07 at 14:16:43
 
Dear Readers,

Another interesting note in measuring the AC humm on the outputs.

We found that with the OLD SE84B's even with upgraded parts on a 100db/1w eff. or better it was noticeable.

With the Bias switch for the input tube to the front of the amp it was 1.9mv with it back in the aggressive mode 2.5mv.

This was using a 6n1p or a 6922 like...the quietest tube was a telefunken 12AX7 the ribbed long plate variety, the the Valvo ECC81 and finally the Amperex Japan Orange Globe dual sprocket like spacers - 12AX7-7025.

FWIW - the less gain maybe or the quieter tube the better the output humm.

These are still great units.

Thanks for reading and I hope this helps someone, somewhere.

John D.
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