Jim
70.90.144.126
In Reply to: 12BH7A question posted by KurtP on March 27, 2007 at 06:37:39:
The 12bh7 has better than twice the rp, so it may no do as good a job driving difficult loads, the mu is a little lower (16 vs 20), and it can't handle quite the dissipation (if I remember correctly). You would probably do well to plan the cathode r around the 12bh7, you could then drop in the ecc99, assuming you have adequate heater capacity (pulls a little more I think). Some of this I am dredging from memory, as I am at work and don't have any data sheets in front of me. There is another tube that Kevin recommend, once again from memory, a 6n6p, that has higher gain, better section to section matching, low rp, that is pinned the same except for the heater - you would need to be able to switch heater between 12.6 and 6.3 to be about to do in socket swaps - he prefers it in the raven over the ecc99. Another suggestion of his is to run the raven low and hot - 100v @ 20 ma. This is one of the mods I intend to try. These guys have been using transformer coupling for a long time, and know a lot of good stuff.
Jim
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