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    My experiment rolling driver tubes in VTA st-120 low gain board

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    Andy Jersey

    Posts : 69
    Join date : 2012-09-29

    My experiment rolling driver tubes in VTA st-120 low gain board

    Post by Andy Jersey on Sat Sep 29, 2012 7:28 pm

    I built amp back in June. Basically all new system I had polk audio rti a3 with polk powered sub and an emo preamp i thought it sounded ok but wanted to get full sized speakers. I gave a3s to my son and bought on sale monitor60 series ii . still sounded ok but these speakers were lacking (just the weak link in the system. I sprung for a set of polk rti a9s. I know not true high end but i'd say near high end and what should 've been good enough for what i was doing. Anyway these shouldn't have needed sub woofer and without it i foundi had poor lows. I tried speakers with mac receiver i had and sure enough speakers sounded fine,so i figured amp or preamp. i came by cheapy pre(which didn't sound all that hot but it did have mids and lows. so i blamed it on emo pre which as it turned out probably wasn't my problem., Which brought me to at least now as far as know the only sp-13 Roy has made. Anyway i bought on ebay (planning to build a kit). Ok so, system now loud clear still not right. I contact Bob (in fact i had been in contact with bob through most of the problems and can't say enough about his patience and support. Ok , so i'm a little frustrated, so reading reviews i came upon reality that EH new issue 12BH7 i had in driver positions were severly lacking (being a nube in tube audio i didn't realize the world of tube rolling and characteristics of different brand and different issue tubes) Although now that i've spent i don't know how many hours reading, searching, shopping and listening, i know ,let's say more than i used to. While i know my sonic quest isn't quite over i've learned a good deal about how certain tubes change sound in my application. I understand everybody elses systems are different and also their ears. I do hope this might help at least some of you out there.
    side l center side r result
    amperex 7316 jan6189w A 4/87 amperex 7316 not bad a little bassy lacking some highs
    12au7 philips



    amperex 7316 long blackplate rca amperex 7316 hummed probably bad tube
    12bh7


    amperex 7316 short blackplate rca amperex 7316 too bassy highs fragile weak unnatural
    12bh7


    amperex 7316 long blackplate rca amperex 7316 too bassy highs fragile weak unnatural
    12bh7

    amperex 7316 EH 12bh7 amperex 7316 maybe not quite so bassy highs sound almost like echo on them no true body

    hum gone
    amperex 7316 Jan-89 ge amperex 7316 bass more nuetral highs a little screetchy 9maybe most nuetral so far
    12au7

    amperex 7316 rca black plate amperex 7316 too bassy weak mids weak highs
    12au7

    amperex 7316 amperex 7316 amperex 7316 too bassy

    amperex 7316 telefunken amperex 7316 all highs there bass more nuetral
    12au7

    amperex 7316 cifte 12au7 amperex 7316 best so far best mids best highs bass not overpowering

    amperex 7316 Mullard cv4003 amperex 7316 Sound overall good Bass overpowers mids and highs

    Telefunken 12au7 Mullard cv4003 Cifte12au7 I tried to tame bass with brighter outside tubes It was better with amperex still too
    bassy mids and highs not as balanced (I don't think its good practice to mix outside tubes
    left position mid position right position

    amperex 7316 cifte 12au7 amperex 7316 baseline start best of mid position tests

    ge jan 6189w 8/85 cifte 12au7 ge jan 6189w 8/85 makes bass boomier takes out transparency in mids and highs

    philips jan 6189w 11/87 cifte 12au7 philips jan 6189w 11/87 nicer than ges muddled mids

    eh 12bh7 cifte 12au7 eh 12bh7 bass too boomy highs too screechy mids muddy

    RCA long black plate 12bh7 cifte 12au7 RCA long black plate 12bh7 bass still too strong but better not as boomy mids and highs pretty good (really all in all not bad)
    slight static (very low) by speakers only with ear right by speaker

    telefunken 12au7 cifte 12au7 rca 6189 12au7 pretty pleasant still a little too much bass

    mullard 12au7 cv4003 cifte 12au7 brimar12au7 a little too bassy a little flat in the middle (probably not as bad as it sounds it was ok) not as good as some others

    I don't know why copying excel file skews in this format . i apologize for that. Bob seems to feel i need a brighter tube in the middle to compensate for softness in the highs in my speakers. I'm not sure i agree. Maybe its combo of synergy between speakers and amp. I'm probably going to be dumping tubes at end of experiment, if your interested please ask. hope this helped or entertained.

    Andy Jersey

    Posts : 69
    Join date : 2012-09-29

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by Andy Jersey on Thu Nov 08, 2012 7:56 pm

    Hi as a brief update. I'm running Holland Bugleboy in center position and Teles in side positions (all 12au7s). Very happy with result. I will still try tweaking But this might be it. Nice balance top mids and bass!

    arledgsc

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

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by arledgsc on Wed Feb 06, 2013 8:58 pm

    Hi Andy... Are you still happy with BB center and Teles phase splitters? I'm rolling tubes now after my break in period. I probably can't afford those tubes but on the lookout for balanced set with a little air and bloom. Thanks for the info, Scott

    Andy Jersey

    Posts : 69
    Join date : 2012-09-29

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by Andy Jersey on Wed Feb 06, 2013 9:31 pm

    honestly, what i came to settle on were rca 12BH7s in all 3 positions (long black plates) Some are better than others, i don't know what makes them different, but that's what worked for me, I suspect your speakers might change your results (also your ears). I can tell you something about tendencies of various tube qualities that i tried ( i tried a lot). but in the end its up to you. If you feel like you have too much of something or too little, i could make some suggestions. If your thinking about something in particular, i can tell you what it sounded like to me. That's the best i can do for you. I hope that helped.

    Analog Man

    Posts : 56
    Join date : 2013-09-01
    Age : 54
    Location : St. Louis, MO - On The Hill

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by Analog Man on Sat Sep 21, 2013 9:59 pm

    Hey everybody, Don't get stuck in a vintage box! Try the JJ Ecc802s. Think outside the box.
    This country has far too many people that get set in prescribed ways. Be adventurous no mater what anybody else may think or say. You may discover something that excites you.
    Ok, I am done preaching. You all have a great evening!Smile 

    guentherj2

    Posts : 50
    Join date : 2013-06-22
    Location : Bellingham, WA

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by guentherj2 on Thu Sep 26, 2013 9:35 pm

    What I find interesting about Andy's post is that he uses adjectives that seem less than positive for almost if not all tube combinations. I use a NOS Sylvania 12AU7A in the center with two NOS Tung Sol 12AU7As with a VTA SP12 preamp and a pair of B&W CM10s and the sound is excellent. Great soundstage, clear mids and crisp highs and wonderful full deep bass.

    I have a stock of NOS 12AU7, 5814 and 12BH7 tubes and will no doubt fall victim to the tube rolling bug again so will post any further developments.

    Regards,

    John

    Elrick

    Posts : 71
    Join date : 2012-09-02
    Location : Bellingham WA

    Re: My experiment rolling driver tubes in VTA st-120 low gain board

    Post by Elrick on Fri Sep 27, 2013 12:49 pm

    I'm a believer that if poeple are not doing double blind tests and following an experimental plan of some kind the results are just too subjective to be of much use. Secondly, I would hazzard a guess that differences between identcal tube types within the same manufacturer may be just as great as between different manufactures.

    It's still fun to swap them them out tough.

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