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Adapting (lessening saturation on) p-p o/t's for SE operation <resistor hack ?>

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  • Adapting (lessening saturation on) p-p o/t's for SE operation <resistor hack ?>

    I've now seen a second "somewhat authoritiative" source suggesting that, for low-wattage single-ended service, a p-p tranny can be made more suitable, by use of adding resistance in-line with the plate and Hi-Z transformer primary: It is suggested that a low-value (~20-40 ohm) resistor can reduce dc saturation effects on a non-airgapped core <?>.

    To me, it appears little more than attenuating the current being presented to the o/t, and (while sacrificing power) could have the same effect as changing bias or even simply reducing volume! Has anyone seen this assertion, and moreover; has anyone tested and found any value to this tweak?

    THX!


  • #2
    Makes no sense to me.
    Plate current must equal OT primary current with or without series resistor.
    So if you bias the tube for 40mA plate current, the OT needs to be able to handle a DC bias of 40mA without saturating.
    This typically requires an OT with an air-gapped core.
    A largely oversized PP OT might also work.
    - Own Opinions Only -

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    • #3
      Helmholtz - agreed. That "tactic" seemed little more than shifting a bias point. And ditto; the only mitigating factor that I see for saturation (in p-p trannies) is iron, and higher dc current tolerance. 'Thanks for weighing in.

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