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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


    12ax7 to 12bz7

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    Tom

    Posts : 206
    Join date : 2011-04-04

    12ax7 to 12bz7 Empty 12ax7 to 12bz7

    Post by Tom on Thu Sep 24, 2020 9:59 am

    Hi guys,

    Had fun swapping 12bh7s for 12au7s in my M-125s.
    Now wondering about 12bz7s for 12ax7s in my preamp.
    I've got an old SP-8 built back when you could buy just the kit.
    Xfmr is an Antek T250 that claims 3A of filament current so should be OK there.
    Plenty space in the chassis.
    Anything else I'm missing? Anyone used these?

    Thanks,
    Tom

    MechEngVic
    MechEngVic

    Posts : 81
    Join date : 2019-01-16

    12ax7 to 12bz7 Empty Re: 12ax7 to 12bz7

    Post by MechEngVic on Thu Sep 24, 2020 8:51 pm

    Tom wrote:Hi guys,

    Had fun swapping 12bh7s for 12au7s in my M-125s.
    Now wondering about 12bz7s for 12ax7s in my preamp.  
    I've got an old SP-8 built back when you could buy just the kit.  
    Xfmr is an Antek T250 that claims 3A of filament current so should be OK there.
    Plenty space in the chassis.
    Anything else I'm missing?  Anyone used these?  

    Thanks,
    Tom


    How did you find the swap of 12au7's for 12bh7's? Sound quality?
    avatar
    Tom

    Posts : 206
    Join date : 2011-04-04

    12ax7 to 12bz7 Empty Re: 12ax7 to 12bz7

    Post by Tom on Thu Sep 24, 2020 9:14 pm

    Ha, I'm terrible at the nuances of describing sound quality. Let's instead say I've got a couple sets of old mullards from equipment pulls and like a mullard 12au7 plus the 12bh7 better than back to back mullards. Also switched my RCA cleartops from the m125s back to linestage on the preamp. I think they do a better job there.
    Hope that helps-
    baddog1946
    baddog1946

    Posts : 313
    Join date : 2010-02-03
    Location : Costa Rica

    12ax7 to 12bz7 Empty Howe to make your own custom circuit boards with a 3-D printer

    Post by baddog1946 on Sun Oct 04, 2020 12:02 pm

    I haven't tried this yet but it looks very promising for DIY crowd to make custom PCB boards with your 3D printer.

    https://www.instructables.com/SLA-3D-Printer-Acid-Etched-Circuit-Boards/?utm_source=newsletter&utm_medium=email
    avatar
    Tom

    Posts : 206
    Join date : 2011-04-04

    12ax7 to 12bz7 Empty Re: 12ax7 to 12bz7

    Post by Tom on Sat Oct 10, 2020 11:07 am

    ^um, ok? Smile

    Anyway reporting back on the 12bz7. Listening now with CSN on the table, the one with Darkstar on it.

    So, SP-8 uses it tubes in series so the BZ is second in line, similar to 12bh7 in the M120. The whole path is sp-8 (12ax7 phono 12au7 line) to m120s (12au7 to 12bh7 to kt120).

    Only change is second 12ax7 position.

    With my best 12ax7, Sylvania made for The Fisher, oh hell yes.
    With 12bz7, more umph, more volume (a surprise), loss of some detail in bass I think. Still pretty dang good.
    With RCA 12ax7 blackplate, detail back but so is the "in your face" feeling I get from these. Kinda annoying.

    So there you have it. I'll keep the BZ in for a while. It's all fun. Very Happy

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    12ax7 to 12bz7 Empty Re: 12ax7 to 12bz7

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