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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


3 posters

    New driver tubes, place in front or rear?

    LeGrace
    LeGrace


    Posts : 388
    Join date : 2016-08-07
    Location : Ontario, Canada

    New driver tubes, place in front or rear? Empty New driver tubes, place in front or rear?

    Post by LeGrace Mon Aug 19, 2019 12:12 pm

    Came across a NOS tube sale. One of the items on sale is NOS RCA 12AU7 clear tops. I ordered a pair for my M125's as I've read a lot of positive comments about these. Is it better to install them in the front positions, or rear? Or does it even matter? Just looking to get the most out of them.
    deepee99
    deepee99


    Posts : 2244
    Join date : 2012-05-23
    Location : Wallace, Idaho

    New driver tubes, place in front or rear? Empty Re: New driver tubes, place in front or rear?

    Post by deepee99 Tue Aug 20, 2019 6:10 pm

    LeGrace wrote:Came across a NOS tube sale. One of the items on sale is NOS RCA 12AU7 clear tops. I ordered a pair for my M125's as I've read a lot of positive comments about these. Is it better to install them in the front positions, or rear? Or does it even matter? Just looking to get the most out of them.
    Correct me if I'm wrong (I frequently am!) but the front holes are the voltage amplifier holes (same with the SP-14, and the centre hole on the ST-70s and ST-120s) and will benefit the most from a good tube selection. The rear holes are buffers, and don't care so much.

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    mijohn


    Posts : 119
    Join date : 2013-06-19

    New driver tubes, place in front or rear? Empty Re: New driver tubes, place in front or rear?

    Post by mijohn Tue Aug 20, 2019 9:25 pm

    Sorry to correct you Dave, but as far as the SP-14 is concerned the front tubes are one channel and the back are the other. The pair on the left are the gain stage and benefit from the best tube selection, the pair on the right are the buffer stage. But more relative to this thread you are correct about the M-125's.  Smile
    deepee99
    deepee99


    Posts : 2244
    Join date : 2012-05-23
    Location : Wallace, Idaho

    New driver tubes, place in front or rear? Empty Re: New driver tubes, place in front or rear?

    Post by deepee99 Tue Aug 20, 2019 10:34 pm

    mijohn wrote:Sorry to correct you Dave, but as far as the SP-14 is concerned the front tubes are one channel and the back are the other. The pair on the left are the gain stage and benefit from the best tube selection, the pair on the right are the buffer stage. But more relative to this thread you are correct about the M-125's.  Smile
    MiJohn, you're of course right, too. I think of the "front" of the preamp, i.e. the gain stages, as being on the left-most side, and the two buffers on the RH side as you're looking at the amp's front panel. I think in terms of the LH side being actually the front because the circuits run side-by-side (looking from the front).The layout's a bit confusing till you get used to it.
    avatar
    mijohn


    Posts : 119
    Join date : 2013-06-19

    New driver tubes, place in front or rear? Empty Re: New driver tubes, place in front or rear?

    Post by mijohn Tue Aug 20, 2019 11:15 pm

    Whether it's the front, back, left side or right side , the important thing is you do know which pair of tubes is which! Very Happy
    LeGrace
    LeGrace


    Posts : 388
    Join date : 2016-08-07
    Location : Ontario, Canada

    New driver tubes, place in front or rear? Empty Re: New driver tubes, place in front or rear?

    Post by LeGrace Wed Aug 21, 2019 5:21 am

    Thanks for the info and technical reasoning!

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