In Reply to: RE: Filament hum posted by vinnie2 on September 13, 2016 at 12:42:12:
I tried several, including a simple bridge/filter, a bridge/filter/regulator (linear), and a switcher. Switchers have a potential advantage insofar as their high frequency step-down transformers isolate the DC from common-mode noise on the AC line. It was my experience in every case, however, that DC heating of the 211 sounded dry and lifeless compared to AC, regardless of how the DC was derived. That was the impetus behind my search for a practical (i.e. inexpensive) method of ultrasonic heating.
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Follow Ups
- RE: Filament hum - Triode_Kingdom 19:10:38 09/13/16 (5)
- RE: Filament hum - vinnie2 03:18:40 09/14/16 (4)
- RE: Filament hum - Triode_Kingdom 12:17:24 09/14/16 (3)
- RE: Filament hum - vinnie2 13:05:24 09/14/16 (2)
- RE: Ultrasonic Link - deafbykhorns 10:20:56 09/15/16 (1)
- RE: Ultrasonic Link - vinnie2 12:51:13 09/15/16 (0)