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    VTA Low-Gain Preamp Tube Suggestions...

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    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    VTA Low-Gain Preamp Tube Suggestions...

    Post by arledgsc on Tue Feb 05, 2013 12:01 pm

    Now that my ST-120 has broken in nicely (with Gold Lion KT88s) wondering what you are using for tube #1 with the VTA low-gain board? My brief experience is that I have heard quite distinct differences when rolling tubes. Initially I used a NOS GE 12BH7 which had good drive and lots of air but the upper mids were too forward with lots of sibilance on vocals. But nailed the soundstage and 3D effect. Substituting a new JJ ECC802s which is a long-plate version 12AU7 corrected the vocals but low and high ends a bit attenuated. And lost the "air". Currently running a common JJ ECC82 which has nice balance but not much air (actually probably pretty accurate). So what are you running or like and why do you prefer it over others? For the record I have some NOS RCA long-plate 12AU7s for phase splitters which seem pretty neutral. Thanks, Scott

    Bob Latino
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    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA Low-Gain Preamp Tube Suggestions...

    Post by Bob Latino on Tue Feb 05, 2013 5:12 pm

    Hi Scott,

    I've mentioned before here on the Dynaco Tube Audio Forum that the CENTER (voltage amplifier) driver tube on the VTA ST-70 and VTA ST-120 amps has the most influence on the sound of these amps. On the VTA M-125 it is the front driver tube. Note > All the tubes recommended here are for the lower gain driver board on all VTA wired and kit amps since April 1, 2012. The amps before this date used a higher gain 12AT7 driver circuit. The M-125's have always had the lower gain circuit ..

    Some tubes that you can try in the lower gain version of the board are ...

    1. Mullard CV4003 which is a miltary grade 12AU7
    2. Any USA made (Sylvania, GE or RCA) 12AU7 or 5814 or 5963 or 6189 tube
    3. Any USA made (RCA and GE mostly) 12BH7 or 12BH7A tube.

    I am not going to say "which is better" because many times a tube is system dependent. IOW if your system is a little "dark", a tube with somewhat more output in the upper registers can brighten things up. Right now I am shipping the VTA ST-70 and VTA ST-120 kits (for those that want tubes with their kit) with USA made Sylvania 5814 driver tubes. I have found these tubes to be very neutral sounding ..

    Bob

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: VTA Low-Gain Preamp Tube Suggestions...

    Post by arledgsc on Wed Feb 06, 2013 10:37 am

    Thank you Bob for the suggestions. Yes the #1 center preamp tube. I found some Mullard CV4003s so ordered a few of those to try. I'm intrigued by the "wonderful Mullard midrange" comment in the description of the tube. Have to experience this for myself. Scott

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: VTA Low-Gain Preamp Tube Suggestions...

    Post by arledgsc on Sun Mar 03, 2013 3:11 pm

    I found a tube combo that I really like. The Mullards were a slightly dull sounding to my ears in the numero uno position. I need a little sparkle and air (coloration) while the Mullards are neutral. What I have been using in the past few weeks is a NOS RadioTechnique 12AU7WA from the 1950s. Nice top end tube magic in just the right amount. Excellent bass and midrange. Plenty of gain and drive like a 12BH7 but without the exaggeration in the ones I tried. The RT 12AU7WA is paired with a couple of new JJ ECC802S in the phase inverter positions. Bingo! The JJ ECC802S (gold pin select) is a long-plate 12AU7 varient and very neutral sounding. So I think I found a combo I can live with for a long while.

    About 2 months later... I'm still liking the air and sparkle of the RadioTechnique 12AU7WA in the center preamp position and searching for a complimentary left-right phase inverter to drive the KT88s. I've tried a lot of tubes in the PI position and the favorite I have found is the industrial 5963. It was original designed for 1950s computers! Very rugged and can withstand of lot of abuse like running with zero bias at 5ma so expect to last a long time. The plate voltage rating is 250V max. so works well with the VTA low-gain board PI stages. But not recommended as the center tube with plate voltage around 300V. Sounds good and found a vintage source that sells them for $12.00 ea. The ST-120 experience is only getting better!


    Last edited by arledgsc on Sun Apr 14, 2013 10:35 am; edited 2 times in total

    charlief64

    Posts : 13
    Join date : 2012-12-21

    Re: VTA Low-Gain Preamp Tube Suggestions...

    Post by charlief64 on Sun Mar 10, 2013 12:30 pm

    Just my two centavos. I just put in 3 new Gold Lion 12au7's in my VTA driver for my ST 70 and I'm really impressed. What stands out to me are the silky strings and detailed bass.
    charlie

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: VTA Low-Gain Preamp Tube Suggestions...

    Post by arledgsc on Sun Mar 10, 2013 1:51 pm

    Just my two centavos. I just put in 3 new Gold Lion 12au7's in my VTA driver for my ST 70 and I'm really impressed. What stands out to me are the silky strings and detailed bass.
    Cool beans Charlie! Someday going to give the GLs a try in the ST-120.

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