The Dynaco Tube Audio Forum

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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


+12
CletusB
Ernstmach
Roy Mottram
corndog71
pavlikkkk
markeby
Bob Latino
Peter W.
pichacker
HarryY
LeGrace
cci1492
16 posters

    Pavel's Auto-Bias Board

    pavlikkkk
    pavlikkkk


    Posts : 69
    Join date : 2018-03-02
    Age : 77
    Location : Czech Republic

    Pavel's Auto-Bias Board - Page 4 Empty Re: Pavel's Auto-Bias Board

    Post by pavlikkkk Sun Nov 13, 2022 6:36 am

    New2Tubez wrote:Pavel’s site-
    https://www.audioamp.eu/

    PS, that's my ST120 pictured in post #60

    I have to praise the nice installation
    Pavel

    CletusB likes this post

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    New2Tubez


    Posts : 184
    Join date : 2018-03-20
    Location : NY

    Pavel's Auto-Bias Board - Page 4 Empty Re: Pavel's Auto-Bias Board

    Post by New2Tubez Sun Nov 13, 2022 2:37 pm

    pavlikkkk wrote:
    New2Tubez wrote:Pavel’s site-
    https://www.audioamp.eu/

    PS, that's my ST120 pictured in post #60

    I have to praise the nice installation
    Pavel

    Thanks for all your help Pavel!

    pavlikkkk likes this post

    pavlikkkk
    pavlikkkk


    Posts : 69
    Join date : 2018-03-02
    Age : 77
    Location : Czech Republic

    Pavel's Auto-Bias Board - Page 4 Empty Re: Pavel's Auto-Bias Board

    Post by pavlikkkk Sun Nov 13, 2022 4:38 pm

    New2Tubez wrote:
    pavlikkkk wrote:
    New2Tubez wrote:Pavel’s site-
    https://www.audioamp.eu/

    PS, that's my ST120 pictured in post #60

    I have to praise the nice installation
    Pavel

    Thanks for all your help Pavel!
    I am ready to help everyone bounce
    CletusB
    CletusB


    Posts : 234
    Join date : 2018-02-11
    Age : 69
    Location : Trinidad & Tobago

    Pavel's Auto-Bias Board - Page 4 Empty Re: Pavel's Auto-Bias Board

    Post by CletusB Thu Nov 17, 2022 1:23 pm

    So, I was at the electrical store this morning, minding my own business buying some circuit breakers and stuff for a customer, and came across this cool little gem on the shelf.  Cost about US$70
    ............  of course I had to tear it open to have a peek!! lol!

    A Variac with a monitoring circuit and a motor-drive. You can adjust your output voltage with a trimpot, I set mine to 115v and the input can vary from about 50v all the way to about 200v and the output stays put dead on 115v. At startup, it ramps-up quickly from zero to the preset voltage with no overshoot.  On input variations it's smooth and quiet with no hunting. I really like it, cause my voltage fluctuates wildly from 108V to 128V depending on the load on the grid at the time from the plastics factory across the street and this was pretty hard on my power pentodes.

    Pavel's Auto-Bias Board - Page 4 Stab111
    Pavel's Auto-Bias Board - Page 4 Stab211
    Pavel's Auto-Bias Board - Page 4 Stab311

    Dave_in_Va, 10-E-C and Dale Stevens like this post

    CletusB
    CletusB


    Posts : 234
    Join date : 2018-02-11
    Age : 69
    Location : Trinidad & Tobago

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    Post by CletusB Sat Nov 19, 2022 12:24 pm

    Well,I did not burn the house down! ......Sounds just as great as before, now hopefully with the peace of mind that my bias will always be spot on! Thanks for the assistance Pavel. bounce

    Pavel's Auto-Bias Board - Page 4 Autobi10

    10-E-C, pedrocols and New2Tubez like this post

    CletusB
    CletusB


    Posts : 234
    Join date : 2018-02-11
    Age : 69
    Location : Trinidad & Tobago

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    Post by CletusB Wed Dec 14, 2022 2:40 pm

    Almost a month, rolled a few tubes and I gotta say, I'm loving the auto-bias feature.  I've got the bias LEDs mounted on perfboard, potted in epoxy resin and peeking out the vent slots of the ST-120.
    Pavel's Auto-Bias Board - Page 4 Thumbn11

    mijohn and LeGrace like this post

    CletusB
    CletusB


    Posts : 234
    Join date : 2018-02-11
    Age : 69
    Location : Trinidad & Tobago

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    Post by CletusB Sun Jan 08, 2023 9:16 pm

    I've had those JJ KT88s in a little over a month now and listen to them about 2-hrs per night, hmmm .......I'm really fond of them!

    mijohn likes this post


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