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In Reply to: Re: It could be done. posted by rutton on September 23, 2002 at 11:54:14:
I am supplying 5-6mA per section to the 6900s in the dual differential cascode input section of my amps, after nearly a whole year of thinking about it. Plate resistors are 44K (2W Mills types). So, under steady-state no-signal conditions, the plate resistors drop 220V to 270V, leaving about 150V for operation of the dd-cascode, with the MA2 transformer supplying +400V. The results are just great, fabulous compared to the Mk I front end, which I used to think was superb. But if you look at curves for a 6900 you could conclude that they might do well-er with even more current. I know that others who use them in common cathode or related topologies have used >>10mA current. As to Al's question, that is a tough one. I could have gone either way (6SN7 or 6900) with my current amplifiers, but now I certainly feel no need for further experimentation. In the Atma amps, in the dual-differential topology, the 6900s do NOT have that kind of "hi-fi-ish" sound that I found slightly objectionable compared to good 6SN7s in my Luminescence. In the Atma, there is great sound-staging with the 6900, and mid-range liquidity and depth that I associated with the best of the 6SN7s. But I ain't foolish enough to make the bald statement that the 6900 is "better".
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Follow Ups
- To be precise... - Lew 06:59:47 09/24/02 (0)
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