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Re: I have 7591S (not 'A') - do these also need mods?

Yes, you need to make the changes. JJ 7591s are just as "touchy" about grid leak resistors as EH 7591s are.

Fisher used the "same old" circuit again and again. A 12AX7 section is VERY marginal in the "concertina" phase splitter role, when driving PP 7591s. EL84s - qualified yes, 7591s - resounding no. The drive VOLTAGE requirements of the 2 types are the same, but ... Replacing the 'X7 with a 12DW7 permanently resolves all the electrical issues. Send Jim an EMail and he'll explain, in detail, the whys, wheres, and hows.

Eli D.


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  • Re: I have 7591S (not 'A') - do these also need mods? - Eli Duttman 23:31:03 04/26/07 (0)


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