Help me getting the right 5751 tube

Discussion in 'Amps and Cabs [BG]' started by carl-anton, Jun 23, 2005.

  1. Read the threads and especially the reivews by Kurt Kurosawa and narrowed my search for the perfect tube for my SWR750 to 5751s. But I'm a bit confused about how to tell which are good. Expecially all the "blackplate vs. greyplate" and "3 mica spacers vs. 2" and "gold print vs. green print" seems confusing.

    So which of these looks like the best? Are there anyone that I should stay clear of, or are they all good?

    GE JAN 5751 Black plate (extra support pillars)

    GE 5751 Black plate

    GE JG-5751

    GE JAN 5751 green print (greyplate?)

    So far I've tried only 12AX7s in my amp, and settled for a Ei Elite, which sounds smooth and warm. But I'm allways looking to improve my sound and the 5751 caught my eye. Is the black plate w/support pillars almost 4 times better than the greenprint as the price suggests? Or is it just a matter of availabillity?

    Thanks :)
  2. Le Basseur

    Le Basseur

    Mar 26, 2002
    Hi Carl,
    Sorry for not replying earlier.
    I just read the "5751 digest" whose link you posted and saw the pictures of the four samples.
    I must confess,my oppinion is that we're talking apples and plums here.To keep things short,I'd look at some entire different characteristics than the one mentioned in the Kurosawa's review (wich,despite of his "I'm not an audiophile" statement,uses a very "audiophiliac" approach and language in judging the stuff).
    Before everything else,a 5751 is NOT identical electrically with a 12AX7.Please consult a tube catalog and try to figure out what those parametres mean.
    First,if you really want to link a tube's internal construction with it's "sound",go for the lowest microphonic you can find.But how can this be established,what's the quietest tube,other than by direct testing and comparison?
    Each tube manifests differently in different working conditions,meaning that the same tube might be quiet at,say,2 mA/250V but very microphonic at 3,5 mA/280V.In this case,are you willing to tweak your amp THAT deep?
    If you wanna go the safe way,yes,the more mica spacers in a tube offers the premise of a better mechanical isolation,but this isn't a general rule.
    Second,you said that your SWR originally has a 12AX7/ECC 83 tube type.Don't get fooled by the general fashion of swapping 12AX7s with 5751s for a lower gain and "a smoother sound".This is OK when we're talking vintage amps,those point-to-point wired things,where the resistors where physically bigger than the contemporary flimsy 1/4 watters.
    What I mean is the safe dissipation margins here.
    If you want "the best of the best",than go for a Telefunken ECC803S and you're done....rather tweak your bass,change your playing technique or go for some real, all-tube amplification.
    In the end,one more remark about Kurosawa's test:he says there that he tested those various tubes WITH HEADPHONES.
    No harm here,but I sincerely doubt that,once that a certain bass preamp is played in a normal fashion (through a power amp and a cab),standalone or with the band,those differences shall be heard in such a detailed manner.
    Personally,I come from the high-end world (built tube systems for decades,'till I got sick of snobism and Placebo effects).I'm a pro musician by occupation and,alas,I cannot be easy fooled by any mumbo-jumbo,therefore I stand up every time when I hear or read some BS.
    I sincerely hope I didn't discouraged you too much or,worse,offended you in any way with my lines.To respond strictly to your question,if you have the cash,go for
    If not,buy the green-logo GE JAN.
    In both cases,you'd want to observe carefully the thermal behaviour of the passive components around the tube in your preamp,just to be sure that,in a long-term situation like a gig,the pre won't let you down.
    Best regards,
    Le Basseur
  3. msquared


    Sep 19, 2004
    Kansas City
    Unless you have a serious problem with how your stuff sounds, a tube swap isn't going to drastically change anything in that amp's sound.

    I have an SWR SM-900 and did some tube swapping of my own a couple months ago. I posted my results here:

    I ended up picking a 12AX7 over a 5751.
  4. Thanks alot Le Basseur:)
    There was a lot of new info for me to digest there. What got me hooked on the 5751 was the possibility that they would open up my sound, and make the lo-end a little more warm/tubey/full. Someone described the 5751's as a little 'slower' reacting tubes than 12AX7's meaning they sound a little softer for lack of a better word. That just sounded like to be a good mix with the tight SWR sound.
    I have next to no knowledge of tubes, so it's a steep learning curve for me right now, and I might take in a lot of BS without knowing it. so, thank you for you comments and for throwing a little light on this matter.

    As for the Telefunken tubes, they seem to be pretty hard to get by, and cost a fortune. Any good places to look for them, or is ebay it?
  5. I tried a few 12AX7's myself (only current production ones) and you're right: the difference is minimal. But then again, I don't want a big change. I don't want to 'un-swr' my sound as some SWR owners seem to. On basstasters I really think the SWR amps sounds really good. My only gripe is the low end being a little tight a times. If I could mend that with a new tube, it'd be great. Got some of the way with a Ei Elite 12AX7E, and the describtions I heard of the 5751 sounded like I could go even further.

    Thanks for chiming in.
  6. Le Basseur

    Le Basseur

    Mar 26, 2002
    You're welcome,Carl! my words were correctly interpreted and I didn't offend you...;)

    Historically,the 5751s were used as a front tube in some old Fenders or as a 12AX7 replacement in other guitar amps whose owners intended to use them with a harp (Hawaian guitar).Yes,the 5751 has lesser amplification and "smoothes out" a gain stage...but this is happening in a vintage amp,not in a modern SWR whose character is also determined by the following (solid-state) stages.

    No prob here,mate...:)...what's important is not to be fooled from the very first beginning.
    Yes,they're rare and expensive,thanks to the audiophile world :eyebrow:
    You can find them ocasionally on eBay or,better,make a visit of your local radio-amateur club.Those old guys hide sometimes a fortune in their closets! :hyper:
    Good luck!
  7. No offense taken at all :)

    So, your basically saying (as msquared also did) that the 5751 might not do anything else than lower the gain of my SWR, simply because of the preamp construction?
  8. Le Basseur

    Le Basseur

    Mar 26, 2002
    No,Carl...what I'm saying is that a 5751 in a 12AX7-dedicated circuit shall lower the gain of that stage AND change the sound..but not so obviously like you'd expect (it's not the "toad-to-prince" conversion here).
    Once again,a side effect due to the inherent differences between the two tube types might be a possible weird behaviour (or even instability) of that stage,maybe leading to some fried small resistors (nothing to be scared of,just that your preamp must be serviced after that,if it happens).
    I cannot be sure about that,though,at least not until I see the values/wattages of the passive components implied.
    Could you post me a pic of that PCB section,around the tube's socket?
  9. I get it :)
    Don't have the amp here and I don't have digital camera, so I can't post a pic right now. I'm not expecting big changes, just a little extra something. Thanks for you comments.
  10. Finger Blister

    Finger Blister

    Jul 8, 2003
    I've been using a 5751 green print in my SWR since 1999.

    The green print GE is the one I'd choose.

    No 'stability' issues and the gain is just about the same
    as the stock GT 12AX7A.
    i.e., The gain clip light enters at about the same pot position.

    Provides a focused low and a less brittle high end.
    Sweeter overall with (for lack of a better term) dimension.

    No wierd behavior, instability, or fried resistors
    in 5 years of use in my sm 400-S.


    Golden tone heard by a tin ear is a waste.
  11. gfab333


    Mar 22, 2000
    Honolulu, Hawaii

    I'll be watching your thread with great interest. I was going through a similar exercise with regard to my Eden WT-550 head which comes stock with a Ruby 12AX7 (when I bought it anyway). However, I should say that you are going about it in a much more comprehensive manner, which is great. I was curious to see if I could improve my tube preamp's tone, not that Eden's stock tube sound bad (it actually sounds great). In my view, I was thinking that the stock tube could be improved on with the selection of a more expensive brand name tube.

    I went through a bunch of tubes that I had quick and easy access through friends or dealers including a NOS RCA 12AY7, GT 12AX7R3 Russian, GT 12AX7M Mullard, and a Mullard 12AU7. When I A/Bed each tube with the stock Ruby tube and was surprised at the outcome of my comparison test. The Ruby sounded the best to my ears as far as overall musical tonality, lows/mids/high frequencies, warmth, and gain.

    The sonic differences between the stock tube and the others ranged from slightly noticable to barely noticable. Some tubes seemed to have a higher gain level while others were softer, still others had more mids but less highs; another tube had more highs and mids but less bottom. I can't remember the details of each tube. In the final analysis, I'm personally satisfied with the stock Ruby in this head as far as tone goes. I'm wondering if Eden had Ruby manufacture the tube to a certain specification; maybe that's why the Ruby sounds best in my head.

    A number of friends suggested that I try 5751, but I never got around to it. I look forward to reading about your findings. Best wishes on your quest for tone!
    :cool: :D :cool:
  12. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine

    FWIW, when I tried different tubes in my Navigator preamp, I really couldn't hear much of a difference, either - although I certainly do hear a difference with different tubes in other tube preamps I own.

  13. Thanks gfab333 and Finger Blister :)
    I think I'll should have tried a new tube in a week or two, depending on how long it'll be in the post. I have yet to hear back from a dealer or two, but I'll try either the blackplate GE or the greenprint. Unfortunately I called a shop regarding a nameless 5751 on their site. The shop turned out to be the importer of Aguilar gear. Now numbers like 659 and 680 have been taking over 5751 in my head. Though other numbers, much higher, also entered my mind (DB750=3500$ in DK)... I think I'll try out the tube first ;) (though I got a realistic and tempting offer on a slightly used 659 with power amp. But I have concerns that I might not like it's darker tone, and reviews aren't all positive. The DB750 and 680 are way over my economic powers, but the 680 sound pretty perfect on basstasters. Tombowlus, if I remember corectly you have a 659, right? Any thoughts regarding SWR and the 659?)

    gfab333, what tube is it in the pic?
  14. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I don't think that I have played through an SWR 750, but relative to the SWR products I have played, the DB 659 is tonally quite different. My personal tastes are such that I strongly prefer the 659 (or 680, or one of several other preamps), but again, it's a fairly different sound from the "typical" SWR product.

  15. Ok, thanks. I'll probally have try it out some day, but it might be to far away from what I want.

    Could you describe the difference a bit? Darker, fatter etc.
  16. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    The 659 is a full sounding preamp, with an authoritative tone. It has nice high end sheen and a hint of growl in the low mids. With the Sovteks that were in it when I bought it from boogiebass, the mids seems a bit "wooly." But when I threw NOS Telefunkens (smooth plate) inside, the mids became much more musical, clear and articulate.

    Hope this helps, Tom.
  17. does :) Thanks. A last comment on the 659 vs. the 680?
  18. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    The 680 is more pristine and clean sounding, with seemingly endless frequency range. It has no lack of fullness (though the 659 may therefore have an overabundance?), and sounds very open and airy, with great "texture" to the tone. The EQ is quite flexible, of course. By contrast, the 659 is more full sounding, and a bit more focused and authoritative in the midrange. It does not do "clean" to the same level of sanitation, but then again, the 680 doesn't yield the same grit/grind/growl that the 659 can. BTW, the 659 does not do an over the top overdriven tone, but it can dial in a nice serving of the three "G's" as mentioned above.

  19. Very cool info. The 680 sounds so much like something I would like. Unfortunately ;)

    Thanks Tom!