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192.28.2.17
In Reply to: Well basically... posted by Nickel Core on May 7, 2007 at 12:41:22:
have you checked what kind of hum you get with AC heating on the 300b? I am soon going to try some cancellation methods to get mine down lower than it is currently. this is also a 3stage 300b amp, but only 2 are dht (choke loaded 6b4g driver).
Follow Ups:
hello zarniwoop !an idea. why not sub in a 2a3 for the 6B4G so you can run your driver on AC at 2.5 VAC / 2.5 A.
that should sound even better than a DCed Ef 6B4G I would guess.
hi,
Even with a 2a3 I doubt it would work to use AC heating. In theory, the hum from the two ac-heated dhts should cancel somewhat when they are coupled in series as common-cathode stages. guess the driver overwhelms that effect since its amplified further.i'm going to try to stay with AC on the 300B. I still maintain that its not possible to get a really quiet amp with AC heating dhts (in SE) without some tricks. Maybe at 2.5v its tolerable.
Well, with the 10 turn hum pots I'm able to get down to unhearable hum level at my listening position with my 97dBA speakers (you can feel some 50hZ hum when touching the cones though).
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