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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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    Permanent Bias Meters?

    Rbertalotto
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    Rbertalotto


    Posts : 98
    Join date : 2021-02-25
    • Post n°1

    Permanent Bias Meters? Empty Permanent Bias Meters?

    Post by Rbertalotto Tue Mar 02, 2021 6:47 pm

    I will be starting the build of my VTA ST-120 this week. I want to add permanent bias volt meters in place of the sockets on the front panel. Maybe a wood cabinet. I see small round meters on Ebay with a scale of 0-3 volts. Will this be enough resolution to set bias? They also offer 0-1 volt meter. I understand the bias voltage is around .50v?
    Any schematic on how I would wire them or simply wire to the test points that were connected to front socket with a SPDT /center off switch for each meter? (2 meters)
    Any suggestion of a round analog meter would be appreciated.
    Another option might be VU meters but this looks more complicated. Is there a relatively easy way to accomplish VU meters?
    Thank You

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    scrotuss
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    scrotuss


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    Join date : 2012-12-16
    • Post n°2

    Permanent Bias Meters? Empty RE: Bias Meters

    Post by scrotuss Thu Mar 04, 2021 4:06 pm

    Rbertalotto wrote:I will be starting the build of my VTA ST-120 this week. I want to add permanent bias volt meters in place of the sockets on the front panel. Maybe a wood cabinet. I see small round meters on Ebay with a scale of 0-3 volts. Will this be enough resolution to set bias? They also offer 0-1 volt meter. I understand the bias voltage is around .50v?
    Any schematic on how I would wire them or simply wire to the test points that were connected to front socket with a SPDT /center off switch for each meter? (2 meters)
    Any suggestion of a round analog meter would be appreciated.
    Another option might be VU meters but this looks more complicated. Is there a relatively easy way to accomplish VU meters?
    Thank You

    I actually had a similar idea and  picked up some small digital meters from mr. Bezos that were 0-30V scale, but require a power source to read under 3V  (i might use a battery to keep it simple).  Have done nothing with them as of yet.  Could you actually use permanent meters with an autobias board, just to make certain that it's working correctly?
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    Rbertalotto
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    Rbertalotto


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    • Post n°3

    Permanent Bias Meters? Empty Re: Permanent Bias Meters?

    Post by Rbertalotto Thu Mar 04, 2021 4:58 pm

    My understanding is that the auto bias boards didn't work out to well and are no longer offered?
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    Bob Latino
    Bob Latino
    Bob Latino
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    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°4

    Permanent Bias Meters? Empty Re: Permanent Bias Meters?

    Post by Bob Latino Thu Mar 04, 2021 9:56 pm

    Rbertalotto wrote:My understanding is that the auto bias boards didn't work out to well and are no longer offered?

    The AutoBias boards did work OK when installed but there were issues with long term durability. As such, Roy and I do not offer the AutoBias boards on the Tubes4hifi web site anymore.

    Bob
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    stevebro
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    stevebro


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    Join date : 2013-06-25
    • Post n°5

    Permanent Bias Meters? Empty Re: Permanent Bias Meters?

    Post by stevebro Sat Mar 06, 2021 5:52 pm

    Hi, would be interested to hear how this goes as I fancy doing the same thing on my ST70 amp.
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    scrotuss
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    scrotuss


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    Join date : 2012-12-16
    • Post n°6

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    Post by scrotuss Sun Mar 07, 2021 5:37 pm

    I guess, in the end, the autobias module probably violates the philosophy that attracted us to Dynaco products in the first place;  budget audiophile, K.I.S.S., and the old adage "perfection is the enemy of good enough".  A quick and easy way to check bias without dragging out the meter accomplishes the task of correct biasing without the complication of a potentially failure-prone circuit.  Hence the idea of permanent bias meters (along with the fact that they can be made to look cool!).  Has anyone out there done it yet?
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