12AX7 tube

Discussion in 'Amps and Cabs [BG]' started by Davidoc, Oct 27, 2001.

  1. What's the difference between 12AX7, 12AX7A and 12AX7C?
  2. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Not sure, but ANY 5751 tube used in place of a 12ax7 or 12ax7a will sound better in a bass preamp.

    The difference is amazing.
  3. Captain Awesome

    Captain Awesome

    Apr 2, 2001
    Do those fit in a standard 12AX7 socket?
  4. VicDamone


    Jun 25, 2000
    Ditto on the 5751. I took Donne's advice and replaced my Navigator's 7025 with a Sylvania 5751 and now have a much more noticable overdrive effect, cost $10.
  5. I also use a Navigator preamp. I tried a lot of different 7025/12AX7s, and I liked the original Sovtek 12AX7WA that came with it the best. Do you like the 5751s for the overdrive sound only?
    What other reasons do you like them better.
    There has been a lot of talk on this, but this is the first time I have heard of 5751s being better. I am very curious.
    What sound do you go for?
    Thanks, Bob
  6. VicDamone


    Jun 25, 2000
    First of all I didn't say the 5751 was better, it is however different in that with the knob full right I get rich overdriven fuzz effect which I guess is what I was after. I rarely use this but the original valve did so little to change the color of the preamp I assumed it had gone bad. I replaced it with a new 7025 and got the same extremly suttle change in character.

    I belive the Navigator is billed as a hybrid tube preamp but IMO it doesn't sound anything like a tube preamp which is just fine with me. Ultimitly I want to hear the instrument not the rig and tubes and or the Navigator are to colored for that goal. Still the Navigator is a unique preamp and I don't think I'd part with it.
  7. I am always looking for a tweak. I'll try to pick one of the 5751 tubes. I like to push my equipment, and I seem to like the subtle grind the Sovtek gives. Maybe also, the 5751 sounds that way with the control far left.
    I also feel that many makers are now voicing their preamp circuts around the $10. Sovtek tubes. I did, howvever like the 12AX7WA better than the WB one.It stayed together better in the lower notes.
  8. VicDamone


    Jun 25, 2000

    Wouldn't it be nice if the manufactures went right on voicing there equipment around a particular tube but provide easy access to the tubes for different tonal tastes. Deracking and removing ears and covers is a major pain. Isn't there a preamp that hangs the tubes off the back pannel?

    Grind, thats the word I was looking for to describe the 5751. So was it Eden's intention to offer this grind or simply to have it sound tubey?
  9. Phat Ham

    Phat Ham

    Feb 13, 2000
    The Kern IP-777 has that. The problem with having the tubes stick out the back is they are much less protected, making the preamp more fragile.
  10. Umm, I always heard that the 5751 had LESS gain, and thus less overdrive, than 12AX-type tubes. I think I agree with this. What gives?

  11. Yep, the 5751 has less gain. So depending on the circuit, you may have to turn up the volume more to get the same output level, which may overdrive something more.

  12. What do you mean "something more"? You mean something else?

    If you get less gain from the 5751, is that like a 12AU7, or a 12AT7 ?
  13. Yeah, my bad, something else in the signal chain has to work harder to make up for the total loss in gain, is what I meant. Like both halves of the 5751 have to be driven harder to produce the same output level as the 12AX7. So there's more creamy filling to go around.:D

    5751 is like between 12AX7 and 12AT7.
    Compare the Amplification Factors (greek letter "mu", looks like a cursive u) >> 100 for the 12AX7 versus 70 for the 5751 versus 62 for the 12AT7.