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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ?

    Austuriano
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    Austuriano


    Posts : 7
    Join date : 2012-11-13
    Age : 75
    Location : Tampa, Florida
    • Post n°1

    Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ? Empty Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ?

    Post by Austuriano Fri Oct 04, 2013 6:28 am

    Has anyone used wirewound pots on the VTA upgrade boards for bias. The advantage of the wirewound pots is a higher wattage rating, along with a hefty price.  A post at Audio Asylum said they encountered a weird resonance that they attributed to a by-pass cap interacting with the wirewound pot?  Cermet are less expensive, but I have never seen any rated above 1/2 watt, which may be adequate.
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    Bob Latino
    Bob Latino
    Bob Latino
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    Location : Massachusetts
    • Post n°2

    Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ? Empty Re: Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ?

    Post by Bob Latino Fri Oct 04, 2013 8:20 am

    You don't need higher rated pots than the 1/2 watt units than that come with the VTA driver board. Those pots only look at 30 to 50 volts and are not really stressed while the amp is playing .. No one (to my knowledge) has ever "blown" a bias pot while their amp was playing ..

    Bob
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    Roy Mottram
    Roy Mottram
    Roy Mottram
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    • Post n°3

    Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ? Empty Re: Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ?

    Post by Roy Mottram Sun Oct 06, 2013 11:50 pm

    I've been using the cermet pots for 25+ years now on these VTA70 and MK3 boards, NEVER had a problem with any of them!
    Bourns 3386P or equivilent
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    Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ? Empty Re: Bias pots: cermet or wirewound for the VTA MKIII/IV upgrade boards ?

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