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EZ81/6CA4 Heater Question

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  • EZ81/6CA4 Heater Question

    I've been looking at some Vox AC15 schematics lately. The rectifier, EZ81/6CA4, uses the same heater winding as the rest of the tubes. The winding isn't center tapped and I don't see a virtual center tap like Fender's two 100 ohm resistors. Doesn't that make for a very noisy amp? Maybe I'm missing something.....

  • #2
    Check over at the 1st stage tube, eg EF86, you'll probably find that one leg is shown as being grounded there.
    I agree it's not really helpful, rather it's a bit of a crossover between a layout and a schematic for the path to be so convoluted.
    My band:- http://www.youtube.com/user/RedwingBand

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    • #3
      I wonder if you could make a virtual center tap with two resistors with the rectifier on the heater string. Would that screw something up with the rectifier?

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      • #4
        That should be fine and would be a useful improvement.
        I think most modern versions are arranged like that, even if described as exact clones.
        My band:- http://www.youtube.com/user/RedwingBand

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        • #5
          Yeah, I see now that it's indirectly heated. Should be OK. Thanks!

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          • #6
            Find out if it is even an issue in your amp, before going to redesigning the circuit. All those problems with grounding the heaters are POTENTIAL hum sources, not guaranteed ones.
            Education is what you're left with after you have forgotten what you have learned.

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