The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all products and all products

    Auto Bias?


    Posts : 1463
    Join date : 2008-11-30

    Re: Auto Bias?

    Post by tubes4hifi on Mon Apr 10, 2017 5:18 pm

    seems like this thread took a huge left turn about halfway down.
    One of the problems with AutoBias, which is why I never added it to my amps, is kind of like the problem that Curcio created with his regulated screens.
    Sounds like a good idea. But if you regulated the screens, and the B+ changes (which it does constantly, with the variable AC input from the nearest power pole)
    then it throws the circuit out of balance. Screens are stable and steady, everything else is changing.
    So AutoBias . . . only if the AutoBias is derived and based on the B+ voltage. I haven't seen one that is yet (it likely is on those high priced amps from China going for $4K instead of $1K).
    You take a $50 circuit running off the filament voltage, you may have stable and steady bias, but your B+, and screens, and cathodes are changing with the incoming AC.
    I'll keep my screwdriver and DVM handy, and keep the motorcycle, and forget about the WAF, thanks. BTW, my wife loves my tube gear !!!


    Posts : 331
    Join date : 2014-03-13
    Location : Philadelphia

    Re: Auto Bias?

    Post by audiobill on Mon Apr 10, 2017 7:12 pm



    Posts : 333
    Join date : 2014-06-23

    Re: Auto Bias?

    Post by Dogstar on Fri Apr 14, 2017 10:47 am

    Seeing as how the new Dynaco ST-70 Mk 3 has an auto-bias capability how hard would it be to incorporate something like that into a VTA ST-70?

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    Re: Auto Bias?

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