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Filament voltage .. AC/DC?

Discussion in 'Amplifiers' started by GnG8d, Oct 25, 2011.

  1. GnG8d

    GnG8d Well-Known Member

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    Is there an advantage of one over the other for the heater voltage?


     

  2. office888

    office888 Active Member

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    AC can produce filament hum.
     
  3. GnG8d

    GnG8d Well-Known Member

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    Is a simple choke sufficient for filtering after rectifying? Regulation?
     
  4. Kamikaze

    Kamikaze Active Member

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    AC filaments if directly heated use a centertap on the transformer to complete the cathode circuit. They have extremely tiny amounts of hum.

    I've heard DC will wear out a filament quicker due to more emission on one side of the filament. Not sure though.

    Standard practice on most tubes is to use AC and sleep at night like a baby.
     
  5. GnG8d

    GnG8d Well-Known Member

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    How about indirectly heated? Stiil AC centertapped?
     
  6. Kamikaze

    Kamikaze Active Member

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    Some like the 12AX7 are but it does not complete the cathode to ground circuit as in directly heated tubes.
     
  7. GnG8d

    GnG8d Well-Known Member

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    So a YC156 for example could use a center tapped xformer, center tap to ground, a pair (or single) bifilar choke, and delta fed Rf through the caps.
     
  8. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    WV7U YC156 Amp

    359
    You may have already looked at this...
    If not this Gent builds some real killers.
    All the Best
    BJ

    http://www.directivesystems.com/YC156.htm

    This link may be a little closer to your needs...still looks like an interesting build...but the control circuits and warm-up controls seem a little tedious to my liking.
     
    #8 BJ radionut, Oct 26, 2011
    Last edited: Oct 26, 2011
  9. GnG8d

    GnG8d Well-Known Member

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    Good links. I saw another guy who was using 2 bifilars in parallel and it had me confused for a second, but it just dawned on me that he was increasing the amperage capacity.
     

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