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pre amp tube for SWR amp

Discussion in 'Amps and Cabs [BG]' started by bassicstu, Jun 27, 2007.

  1. bassicstu


    Jun 27, 2007
    On another bass guitar forum, somebody said the best sounding preamp tube for an SWR head (I got a 350x) was a blackplate NOS (new old stock) RCA 12ax7. I'll post here to let as many people as possible know I agree.
    I had never heard of a 12ax7's before. 12ax7a's tubes are an industry standard. I assumed it was a mistype. Did some research and found out that 12axy's are an earlier version of the 12ax7a's something to do with warnup. (wake me up when you're through)
    Anyway on his say so bought a single RCA blackplate 12ax7 on ebay for $20 delivered. What the heck I've wasted more than $20 on ....... you fill it in.
    Put it in today and the amp just made a quantum leap in sound.
    Tighter. more punch. Holy cow who'da thought a preamp tube would make such a difference.
    Try it. Check out Bassdogs.com for the first post.

    peace stu
  2. seansbrew


    Oct 23, 2000
    Mesa AZ.
    I have tried at least 5 different kinds of 12ax7 tubes in my SWR SM-500. Most of the tubes I tried did not have a dramatic affect on the tone/character of my amp. Except for the Tungsol tube, It made the amp sound more musical. It also gave me alot more headroom, I do not have to ad as much gain (dont know if that's good or not).

    I do not have any experience with the RCA tube, but I can definetly recommend the Tungsol 12ax7 as another tube that works well with SWR products.
  3. msquared


    Sep 19, 2004
    Kansas City
    I did the tube swapping thing when I had an SM-900. The results were astounding. I think the magic tube for me was an Amperex Bugle Boy.
  4. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    It may sound too simple, but I found a mesa-boogie 12ax-7 was WAY better than the stock tube. Rolling those babies definately matters....
  5. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I found a NOS 5751 sounded much fatter and clearer than the stock 12AX7.

  6. Tweaking your sound with various preamp tubes can be a very interesting and absorbing project. There is a tremendous amount of information available in this forum and else where, and sorting out the shine from the shine-o-la can be daunting but fun.
    amp forum 12ax7 search

    It can also get expensive. Even the most experienced ebay sniper will quickly find themselves with several hundred dollars worth of carefully collected, tissue paper wrapped tubes. Several years back, while discussing SWR preamp tubes with a local tube amp guru, he asked me if I wanted a tube or a hobby. He then reached under the counter and pulled out a new EH12AX7. I took it home and found to my surprise (and chagrin) that it did exactly what I wanted it to in my SWR ST220. It took some of the edge off the extreme highs and brought the mids forward just a bit. All for the grand sum of $10.

    Since then I have thought about selling my collection, particularly since the audio manufacturers seem to be finding a way to get tube warmth without a tube. But not yet, not quite yet. For now I think I’ll get out my old shoe box and gaze with fondness (and satisfied avarice) upon my smooth, square and black plates, my triple micas and halo getters. :smug:

  7. iriegnome

    iriegnome Bassstar style Supporting Member

    Nov 23, 2001
    Kenosha, WI 53140
  8. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Thanks Joe...you reminded me....Duh....I meant EH, Electro-Harmonix!!!!


    I was stunned by the improvement. Probably no one else noticed, but hey!!!
  9. seansbrew


    Oct 23, 2000
    Mesa AZ.
    The EH tube works really well with the SWR pre-amp. I also felt that it added some mid warmth.
  10. iriegnome

    iriegnome Bassstar style Supporting Member

    Nov 23, 2001
    Kenosha, WI 53140
    Well, I just spoke to Doug at http://www.dougstubes.com and I bought a Electro Harmonix 12AX7 and a JJ ECC-83s
    I am hoping one of them will work for me. I had also bought 3-12AX7c's thinking they would work, but for me they sounded like crap
  11. An ECC83 IS a 12AX7.
  12. yamaha


    Apr 7, 2006
    I tried a few in my grand prix, and decided on a jj tesla.
  13. iriegnome

    iriegnome Bassstar style Supporting Member

    Nov 23, 2001
    Kenosha, WI 53140
    Sorry to differ, but they are different. Just because the ECC is the Euorpean designation and they are interchangable, they are very different in tonal quality, microphonics and plating. Not to mention they are much different in the high end and mid range. Yes - an ECC-83s and a 12AX7 or 7025 are al similar, but are very much different depending on who made them, what they go into, and a whole sleu of other things.
  14. rockstarbassist

    rockstarbassist Inactive

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF
    subscribed. :)

    BASSKADET Gold Supporting Member

    May 17, 2007
    I just put 4 of those in my SVT III Pro. I got the Russian made ones. I guess the new ones are going to be from China.

    I also bought one Amperex 12AU7WA. New old stock Mil. Spec. I haven't put that in yet so I'll see if that makes a difference.
  16. Hi.

    Interesting. True vintage NOS tubes aside, how can You tell which one is which without taking it apart? You can't seriously believe that the "original" stamp(s) tell anything about the tubes internal structure or tonal characteristics.

    There isn't really that many manufacturers anymore and the special order tubes do exist but are somewhat more expensive.

    You can however tell something about the re-stamped ones, but only within a single re-stamping company and within a certain batch of tubes. Assuming of course that the feller with the tester wasn't havin' a bad day.

    These opinions are obviously IME, AFAIK & IMO as always ;) .

  17. seansbrew


    Oct 23, 2000
    Mesa AZ.
    Actually, SWR used the Tesla tube under GT as original equipment for some time (don't know if they still do or not). I purchased my SM 500 in 1991. This tube really makes the amp HI-FI

    If you ever want to bring out the mids in your amp up, try the EH 12ax7 or the Tung Sol (This is the best tube I have tried). These tubes work really well with SWR pre's.
  18. Again, no, but it's a qualified no. Every difference you attribute to type variation is make/manufacturer variation. The differences would exist whether the tube was labelled ECC83 or 12AX7. 7025's are low microphony 12AX7's otherwise known as 12AX7A's; there is a manufacturing difference across the board. A 12AX7 and ECC83 ARE the same tube.
  19. keyboardguy

    keyboardguy Supporting Member

    May 11, 2005
  20. iriegnome

    iriegnome Bassstar style Supporting Member

    Nov 23, 2001
    Kenosha, WI 53140
    I got the EH 12AX7 and I think it may be good!!! I played on Tuesday with the new tube and it was almost as good as my EEC-83s!! I am excited to play on stage with the new tube to see how my amp performs on a 4 hour set in the heat. :hyper:
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Feb 25, 2021

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