The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    6SN7 adapter for VTA120

    Share
    avatar
    deepee99

    Posts : 1732
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: 6SN7 adapter for VTA120

    Post by deepee99 on Wed May 24, 2017 8:22 am

    Dogstar wrote:I'd like to try out the octal board as well. However once I build the board and install it I really don't want to swap back so I may consider putting into a new amp altogether.

    I only listened to one CD...perhaps 40 or 45 minutes total with the 6SN7 tube installed. One thing I noticed when shutting down was that all three transformers were still cool to the touch. I expected at least the center, power transformer, to be warmer than the other two since but all three were the same.

    This has got to be the only area of serious disagreement ever aired on the Forum between Bob L. and Roy M., the former favouring 9-pin drivers and the latter preferring the octals.
    Having owned both iterations, at some level it's a Ford-Chevy thing. My preference for the octals is that there are some exquisite-sounding new-production 6SN7x -type tubes out there now, including the Chinese CV-181s, which I use, and (though I haven't heard them yet, I hear great reports) the Tung-Sol 6SN7 GTxs that Jim McShane is carrying. Plus you have a plethora of choices of old-stock to choose from. The massive iron Bob L. uses in his VTA amps and Roy in the pre-amps is more than up to the task of the slightly higher current draw for the octals. Like you, I've noticed no appreciable xformer temperature increase.
    avatar
    corndog71

    Posts : 565
    Join date : 2013-03-19
    Location : It can get windy here

    Re: 6SN7 adapter for VTA120

    Post by corndog71 on Wed May 24, 2017 12:09 pm

    A few nights ago I tried Sovtek 6SN7 and while it did ok I found it ultimately lacking. It had a very dull top end. Last night I went back to my favorite NOS RCA 12AU7 and the treble came back! Much better detail on the top end. Overall the tubes I've tried were not dramatically dissimilar aside from the details I've mentioned.

    Dynamically they were essentially the same and I found myself air drumming and tapping my toes to the beat either way. I still want to try some new tubes to see how they compare.

    Dogstar

    Posts : 274
    Join date : 2014-06-23

    Re: 6SN7 adapter for VTA120

    Post by Dogstar on Wed May 24, 2017 7:16 pm

    So....can tube adapters be used to install 6SN7 tubes in all three of the PCB sockets?

    eickmewg

    Posts : 74
    Join date : 2014-08-29

    Re: 6SN7 adapter for VTA120

    Post by eickmewg on Wed May 24, 2017 7:59 pm

    Yes. Before I built up an octal driver board, I did try using three socket adapters with three 6SN7 tubes. That's why I had several extras to pass along. I kept one and you and corndog got one to try. I don't know if I really gained anything using the three adapters but I was wanting to break out the old soldering iron for a construction project and the octal driver board was relatively inexpensive entertainment. I may try to sell my original noval driver board someday as I don't plan to go back to it in the VTA ST120.
    avatar
    arledgsc

    Posts : 466
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: 6SN7 adapter for VTA120

    Post by arledgsc on Wed May 24, 2017 8:27 pm

    Socket adapters are OK but I really wish I had a board with a octal center but two noval sockets for the ST-120 phase inverters. In earthquake country it would not take much of a jolt to knock over a CV-181 sitting on top of an adapter.

    A dual socket build option board would be interesting. You could load either type socket when the board is assembled.
    avatar
    cci1492

    Posts : 87
    Join date : 2016-05-09
    Age : 56
    Location : Bergen County NJ

    Re: 6SN7 adapter for VTA120

    Post by cci1492 on Wed May 24, 2017 11:00 pm

    I've been listening to a pair of cheap Baldwin 6SN7s from 1960 for the last couple of days. It sounds very nice, not sure I can hear a difference between this and the GE 12BH7A or the RCA 12AU7A that I've been using for that matter. But I'll keep listening, to me, it still sounds very clean and detailed.
    avatar
    Kentley

    Posts : 431
    Join date : 2015-03-06
    Age : 65
    Location : Worcester, MA

    Re: 6SN7 adapter for VTA120

    Post by Kentley on Wed May 24, 2017 11:11 pm

    Those cheap Baldwin 6SN7s are more than likely RCA rebrands. And good ones to boot.
    Sylvania and RCA produced tons of 6SN7s from the late forties through the seventies. It was such a commonly-used tube that they never considered it was to become a classic. Maintaining a "brand identity" probably never occurred to them. Thus the wide availability - - and wide variability.

    P.S. TungSol, Mullard, and Amperex did the same thing - they sold many, many tubes to others to sell under many, many different names. These rebrands can often be found at a fraction of the cost of "originals" and can be great bargains. Or not. But I'd rather waste $2 on a bum no-name than $85 on a brand-name with the lettering intact. Lettering, in case I'm mistaken, has no effect on SQ.


    Last edited by Kentley on Wed May 24, 2017 11:20 pm; edited 1 time in total (Reason for editing : Added P.S. {or B.S.})
    avatar
    cci1492

    Posts : 87
    Join date : 2016-05-09
    Age : 56
    Location : Bergen County NJ

    Re: 6SN7 adapter for VTA120

    Post by cci1492 on Thu May 25, 2017 9:18 am

    Those are the adapters you linked to Kentley. The story goes Baldwin and Dumont organ companies had their own QC departments so the bad ones got sorted out before they stocked them for use in production or as spares. I'm guessing the tube cork sniffers just don't like the name. Who knows, makes sense, but at $26 shipped for 2 for my use, they're fine. They do look kind of goofy with those extenders though.

    If I might add, the sound is more organic now....doh!
    avatar
    arledgsc

    Posts : 466
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: 6SN7 adapter for VTA120

    Post by arledgsc on Thu May 25, 2017 9:38 am

    While cleaning up I found an early '50s Zenith chrome dome 6SN7.  It is used but "tested OK" purchased off Ebay.  Surprising good sound with lush midrange, good bass, and believable soundstage.   The highs are slightly rolled off compared the the CV-181 but just a tad.  Vocals are nice with realistic sibilance.  The CV-181s are a little more dynamic but there is plenty to enjoy with this old chrome dome.

    Enjoy the reviews of new 6SN7 tubes.  Keep them coming....

    avatar
    deepee99

    Posts : 1732
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: 6SN7 adapter for VTA120

    Post by deepee99 on Thu May 25, 2017 10:15 am

    I think if you do decide on 6SN7s you should replace your noval board. Extenders are handy but they do make for pretty long tube leads & more exposure to physical/electronic crud and corruption.
    I'm sure Roy can work up a kit for an octal board and/or build you one.

    eickmewg

    Posts : 74
    Join date : 2014-08-29

    Re: 6SN7 adapter for VTA120

    Post by eickmewg on Thu May 25, 2017 11:16 am

    Yes, Roy does offer the octal boards as boards, boards and parts, or completed boards. Cap upgrades are also available. http://www.tubes4hifi.com/ST70.htm
    avatar
    deepee99

    Posts : 1732
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: 6SN7 adapter for VTA120

    Post by deepee99 on Thu May 25, 2017 11:26 am

    eickmewg wrote:Yes, Roy does offer the octal boards as boards, boards and parts, or completed boards.  Cap upgrades are also available.  http://www.tubes4hifi.com/ST70.htm
    By all means, upgrade the caps (within reason, of course). They make a noticeable sonic improvement.

    Sponsored content

    Re: 6SN7 adapter for VTA120

    Post by Sponsored content


      Current date/time is Wed Oct 18, 2017 9:41 pm