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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: Re: Don does use AC on 45 based amps posted by drlowmu on November 13, 2006 at 23:27:46:
One of the problems with dc on a filament is the unbalanced loading. That is, one side of the filament/cathode runs at higher current than the other. The dc across it shifts operating point. What you get is a compound tube that averages somewhere in the middle.Running ac is similar in that the two ends of the cathode swing hi/lo relative to the center. The average dissipation across the cathode, however, is constant. There are no so-called hot spots.
That is why they can sound different.
Yes, 5V 300B is 6dB more likely to hum than a 2A3. But still I think within reason if you design well. I once tried to make an ultrasonic sinewave balanced heater circuit (Royer type), but it failed. Turns out the circuit is only good for reactive loads.
jh
PS - Interestingly I ended up biasing my 2A3 at 50mA. I thought everyone ran them at 60.
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Follow Ups
- AC on 300B - Jim Hagerman 23:26:45 11/15/06 (4)
- Re: AC on 300B - drlowmu 16:00:31 11/16/06 (1)
- Oops - Jim Hagerman 21:38:42 11/18/06 (0)
- Re: AC on 300B - Naz 15:32:17 11/16/06 (0)
- Re: AC on 300B - Jottow2@yahoo.com 06:51:26 11/16/06 (0)
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