1. The Rules have been updated regarding posting as a business on TGP. Thread with details here: Thread Here
    Dismiss Notice

7591A: EH vs JJ vs NOS?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by googoobaby, Jul 27, 2006.

  1. googoobaby

    googoobaby Member

    Messages:
    1,863
    Joined:
    Mar 15, 2006
    Location:
    Seattle, WA
    (I posted the originally in Amps and Cabs, but thought this might be a better place...)

    I just bought an old Gibson GA35RVT powered by a pair of EH7591As. It sounds surprisingly good, especially for what it cost. I've heard that the EH7591As are considered somewhat dubious sounding, and was wondering if people think the JJs are a significant improvement. Ideally I'd like to try NOS, but can't justify the expense at this time.

    Thanks!
     
  2. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    I run 7591A in a '66 Ampeg Reverberocket and a '64 Scott 340-B (stereo receiver). In these setups I prefer the JJ product for new production (for NOS, Sylvania are very nice :)). The EH didn't sound as tight or balanced as the JJ. Can't give a lot of specifics though... was over a year ago that I did the comparisons.
     
  3. googoobaby

    googoobaby Member

    Messages:
    1,863
    Joined:
    Mar 15, 2006
    Location:
    Seattle, WA
    Thanks! I greatly appreciate the input.
     
  4. lexluther

    lexluther Member

    Messages:
    63
    Joined:
    Feb 9, 2006
    Location:
    San Clemente CA
    I have the Epiphone ea15rvt with two ten speakers. The jj7591's had much more head room than the EH. My amp is very close to the gibson with the driver interstage tranny . I subed the driver tube v5 (in your amp) with a 12at7 instead of a 12au7 and the amp woke up from a clean sleep to balls. Nice amp and the tremolo sounds great. Reverb's a little washy. There are 3 different version schematics for my amp gibson was horrible for using the same number for all of them.
    Luther
     
  5. brad347

    brad347 Member

    Messages:
    4,807
    Joined:
    Feb 8, 2006
    Location:
    Brooklyn, NY
    aren't NOS 7591As vanishingly rare? Like didn't some dude from asia come over to the states and buy 'em all in the 80s or something? Seem to remember hearing tale of that. Maybe that was a different tube.
     
  6. googoobaby

    googoobaby Member

    Messages:
    1,863
    Joined:
    Mar 15, 2006
    Location:
    Seattle, WA
    I've heard that as an apocryphal story. You can get them, but for like $150 for a matched pair when you can find them. Heck, the amp cost $275. :)
     
  7. googoobaby

    googoobaby Member

    Messages:
    1,863
    Joined:
    Mar 15, 2006
    Location:
    Seattle, WA
    I didn't mean it as logic. I like this amp so far, but I'm still making up my mind whether to justify retubing it with NOS. Because right now, I'd really rather spend my tube money in my Rivera pre-amp, which has been a trusted partner for a much longer time (and that I'm less afraid of spontaneous combusting :)).

    No offense taken, of course.
     
  8. JDW3

    JDW3 Member

    Messages:
    3,624
    Joined:
    Mar 2, 2005
    Location:
    Below Flint
    A few years ago I bought adapters and installed 6GM5 power tubes in place of my 7591 in my '66 Ampeg. Sounds great. American made tubes. The adapter is neccesary because the pinout is slightly different.
     
  9. mad dog

    mad dog Silver Supporting Member

    Messages:
    10,458
    Joined:
    Feb 23, 2005
    Location:
    Montclair, NJ
    I just had a 60's Sano 250R 2x12 over at the amp techs, It came in with NOS 7591 tubes that tested out fine. There wasn't a whole lot of sound in the amp, but what was there was sweet. He did a lot of tweaking, woke it up bigtime. Last step was to try the JJ tubes. Big difference. It has that distinctive rich clean sound I associate with many Ampegs, very smooth, thick overdrive on top. Great tubes.
     
  10. TheAmpNerd

    TheAmpNerd Member

    Messages:
    1,062
    Joined:
    Sep 23, 2004
    Location:
    Tejas
    Todd,

    Did you trust your ears on this, or did you scope it?
    :AOK

    I had to ask.
    :dude
     
  11. brad347

    brad347 Member

    Messages:
    4,807
    Joined:
    Feb 8, 2006
    Location:
    Brooklyn, NY
  12. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    No buddy, I put on my favorite crystal (you know, the one with powers), waited for a full moon, laid out the Tarot cards next to the Ouija board, muttered my favorite mantra and waited for the tree outside my shop to tell me which was the tube with better karma. I'd have sacrificed a live chicken, but it was just 7591As. Now for EL34s...

    Who needs a scope when you've got such great marketing... err... ears to rely upon?
     
  13. googoobaby

    googoobaby Member

    Messages:
    1,863
    Joined:
    Mar 15, 2006
    Location:
    Seattle, WA
    I received a set of JJs and had a chance to try them. I like them a lot better than the EHs. Thanks everyone for the input!
     
  14. TheAmpNerd

    TheAmpNerd Member

    Messages:
    1,062
    Joined:
    Sep 23, 2004
    Location:
    Tejas
    Buddy <?> ...not in this lifetime.
    It does speak volumes though.


    Like the difference between a guitar player and a musician.

    If you scoped them, what they played might look the same.


    When you heard them...

    ...the guitar player's notes filled the room.
    ...the musician's notes filled each heart and soul in the room.

    Magic indeed.


    and that my friend is the difference between
    a tech who needs a scope to see what he
    or she senses

    and a musician's tech who learns to hear, feel, and understand
    that it cannot be explained just accepted for what it is.

    After all, they are ALL just notes now aren't they?

    And this is why there are certain magical amps
    magical instruments, magical planes, etc.

    A Strad is just a violin.


     
  15. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    So I've been trying to keep this at least a bit tongue-in-cheek and avoid the flame war, but I've had enough of the slander.

    Your repeated posts in response to math and measurement have suggested that I (and others) evaluate and analyze based solely on the math and measurements; that I either don't have or don't use my ears, or that my ears (or the application of 'em) is somehow lacking.

    The implication, as I read it, is that either I personally, or those of us who understand and apply math and measurement don't understand the music. If that is what you intend to say, it's both insulting and uninformed.

    From my point of view, having trained ears is a prerequisite in any case. You can repair or copy amplifiers with surprisingly little understanding of how they actually work. However, a bit of applied engineering allows one to create rather than repair/copy, reduces or eliminates the "error" part of trial and error and, in so many cases, distinguishes between what is provable and what is hyperbole.

    Designing amplifiers without the technical background, by ear and by ear alone, is a pot-luck venture and, I would argue, the domain of hacks and fools.

    I get that it's all about ears and "musician's notes filling hearts and souls" etc. for you. And when I'm on the bandstand that's all I'm thinking about too. When I'm at the bench or doing design I don't suddenly forget how to play guitar, or what things sound like -- but I can also bring all those years of training and education, all those odd text books from the 40's and 50's, all those years of doing the job to the bench with me.

    So yeah, when you try to tell me that you can't explain everything you can hear, when you avoid or ignore the technical "because it's all about what you hear", it leads me to suspect that you don't really get how these devices work. There were some old posts by you that tend to confirm that suspicion, but I'll leave that research as an exercise for the reader.
     
  16. TheAmpNerd

    TheAmpNerd Member

    Messages:
    1,062
    Joined:
    Sep 23, 2004
    Location:
    Tejas
    I said nothing slanderous, nor have I written
    anything libelous.

    For the former,
    it does appear that way at times. For the latter, I have described my
    own challenge, being more then two standard deviations more sensitive
    than most in some of my hearing.
    That is not what I intend to say at all.
    In general we agree.
    I suppose it is about "hear" we diverge.
    Your presuppositon is that
    I don't, or that I'm not well read?

    No, I'm honest, I can't explain it nor can I quantify it. I don't have the
    lab nor the resources to measure it, nor do most folks either.

    As far a research, I recall a post with a link from you, depicting various capacitor types from which you made a very false conclusion from the
    data presented, based upon your own biased flavor of cap. Additionally, other false statements by you come to mind.

    HOWEVER

    I really don't have time to be specific, but you get the drift.


    AND

    I am not Immune to finger or brain flatulations, some of which may
    occur in altered states of mind--Ja, Ich sehr Gern Meiner Bier.

    On the whole though, I try to push the envelope and be experimental,
    which, as those of you who have tried, result in some lest than notable
    results.


    Just ask that Wizard guy...


    ...you know the one from Menlo Park!



    Todd,

    For heaven's sake, please don't think
    I've been sucked into ALL that Audio-Phoolery!


    :AOK

    PS - Do you need any $1000 electrolytics?
    Get 'em while you can, these working musicians
    are buyin'em like fashion models snort coke.



     

Share This Page