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12AU7 in V1?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by prof2915, May 27, 2005.

  1. prof2915

    prof2915 Guest

    Hi

    Years ago i tried a 12AU7 in a (rack) Chandler Tubedriver, but as I wanted to use it for overdriven stuff I took it out and replaced it with a 12AT7. (which I found to be much more dynamic than the original 12AX7)
    The reason for doing this was that it was almost impossible to drive the tube (12AU7) into distortion.
    On the other hand it delivered among the fullest and fattest tone that I´ve ever heard!

    I´m going to replace the tube in V1 (works only on clean channel I belive) in my Laney VC30 with something lower gain. The amp goes into breakup to early, and I´m looking for a warm clean sound close to the point of breaking up but without really doing so.

    I´ve got an 12AT7 that I will try and I´ve been reommended the 12AY7 (which I belived to be the more or less the same as the 12AT7?...) and the 12AU7.

    Can´t afford them both right now...
    Which one would be the best buy: 12AU7 or 12AY7?

    /Peter
     
  2. stratopastor

    stratopastor Member

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    Hi Peter

    Maybe someone else with more knowledge will give you an answer, but I THINK this is something no-one can help you with. Either tube will get you closer to what you want. No-one can tell you which one you will like more. Buy one tube and try it.

    If there IS someone out there with a 'real' answer, I they will write something if only to correct me!

    best wishes

    SP
     
  3. prof2915

    prof2915 Guest


    Hi.

    I know that questions like this one are hard to answer, but as there´s a particular goal I´m aiming at (more clean headroom and less "early pre amp breakup") I hoped it should be easier to answer compared to if it only came up to personal taste.

    Thanks for taking your time to answer my question!

    /Peter
     
  4. TAVD

    TAVD Guitar Player Gold Supporting Member

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    You might also want to try a 5751 tube. Experiment.
     
  5. Fuchsaudio

    Fuchsaudio Member

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    All circuits will respond differently to changes in a tube. A 12AX7 designed circuit will react differently with another tube in it. Sometimes it's better for a particular player's ear or the tone he's shooting for, but it does change operating voltages throughout the amp, as well as the overload and gain structure of the amp. As long as the pinout is the same AX7, AT7,AU7, AY7, 5751, etc. you should be fine.
     
  6. prof2915

    prof2915 Guest

    Hi

    Yes on monday I´ll experiment with tubes that I´ve got!

    Thanks.

    /peter
     
  7. prof2915

    prof2915 Guest

    Well, I now know what you mean... The 12AU7 that sounded rich and full in one amp, delivered a clear and snappy tone in another...

    Obviously there´s no general anwers to this type of question.

    /Peter
     
  8. LHanson

    LHanson Member

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    My entire knowledge of tubes comes from Aspen Pittman's book, FWIW.

    He says a 12AT7 is ruggedized, and is best used in reverb drivers and phase inverters. He says it's not very good sounding in audio circuts. I have never tried, myself, to use a 12AT7 in an audio circuit, but I did recently try a 12AY7 in V1 of my Boogie .50 cal +, and it did reduce the gain of the lead "channel" and open up the rythym "channel" quite a bit.
     
  9. darkwave

    darkwave Member

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    I'm going through the same process with a Yamaha T-100 (the Soldano model) right now. I tried a 12au7 which sounded a bit dull and a 12at7 which was better, but still not very rich. The Sovtek 12ax7LPS just sounded better than these other tubes even though it had too much gain.

    I called Lord Valve and he suggested the 5751 for audio uses as well. Unfortunately I blew a power tube and now have to wait until it is checked over and rebiased before I can try it out...

    -Douglas C.
     
  10. drano

    drano Member

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    I'd would go with Dr. Fuchs' advise up above over Dr. Pittman's here. (For one thing I love his amps.) I can't find info on the 12AY7 to fit it into the line-up but these twin-triodes go from not much (if any) gain in the 12AU7 to some in the 12AT7 to a lot more in the 12AX7. More gain / less headroom, isn't that how it generally works?

    I just picked up some Sylvania 12AT7s on ebay that were sold as new tubes for about $4 per tube. They got here and looked absolutely new. I tried them in my Velocette and they sounded better than any of the 12AX7s I've tried so far - cleaner, fatter, warmer. So I don't know where Mr. Pittman get's the idea about them not sounding good. Maybe if HE makes 12AT7s HIS might be "ruggedized" and may sacrifice some tone but I'm not sure why that would apply to 12AT7s in general.

    I don't know how much the inverter cares about gain but some tube experts say it wants balance between the two triodes so you might not be able to tell the difference between any balanced twin triodes: U, T, X, Y, whatever, in the inverter socket.

    If anybody can correct me on this please do.
     
  11. prof2915

    prof2915 Guest

    Hi
    I started this thread (as well as a couple of others discussing "related problems") so now I´ll tell you what I ended up with (this reply has been posted to the other threads as well, so you might have seen it...)

    Here it is:

    So, now I´ve done some testing.

    -I settled for a 12AT7/ECC81Y from RubyTubes in V1.

    The result is less preamp distortion (as well as a little less volume) and better clean headroom.

    - I ended up with a 12AU7A from National GoldLine in V2. :eek:

    This might be considered as a strange chocie, but the reason for this was that the "drive sound" was too fat :confused: - in a muddy way - when compared to the clean sound.
    The volume and distortion is now MUCH lower, but as I use pedals for my distorted sounds it was nice to have the drive channel deliver a nice and clear breakup sound, rather similiar to the clean sound. (as this is a 30 watt EL84 amp, the clean sound is close to the point of breakup as well)

    - I tried some tubes in V3, but changed back to the original one.

    - I´ve tried a cleanboost in the effectloop, and by doing so I can coax a little more "clean" volume from the amp. My RC booster is still in front of the amp, but I might get another one for the loop.

    All together I´m right now much happier with my amp! :D

    /Peter


    Ps The amp I´m referring to is a Laney VC30 "class A amp" ds
     
  12. Fuchsaudio

    Fuchsaudio Member

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    With all due respect to Aspen, that's not a valid statement. In a circuit properly designed for it's use, a 12AT7 can sound as good as any other audio tube. In an application where you simply substitute an AT7 for an AX7, likely not. They are too different a tube to just make a switch like that. I also don't think a 12AT7 is any more "ruggedized" than another similar dual triode. It's a stronger tube (electrically it will swing more current and produce more power), but no different mechanically.

    Actually, a 12AT7 makes a very quiet and linear input stage for a guitar amp or phono preamp, (so does a 6SL7) but try to find either in a quiet enough tube to use it !
     
  13. John Phillips

    John Phillips Member

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    Since no-one else has mentioned it so far, the 12AY7 is very similar to the 12AX7 but has about half the gain. I have one in the first gain stage on the dirty channel in my Mesa Maverick, it was just the ticket - a little cleaner and less spiky but basically the same 'tone'.

    I also don't usually like a 12AT7 in a gain stage, FWIW (at least, one that's been designed for a 12AX7) - I find it becomes a bit 'cold' sounding. But I like them very much in the PI of many amps which were designed for 12AX7s - Mesas in particular - where it gives a much clearer, deeper and more transparent tone.

    12AU7s are much lower gain and more dependent on the circuit they go into, in my experience - I do like the sound of them, but they have too little gain for me normally... although in some amps that's just what you need. I tried one in a Peavey Classic 20 once - normally an extremely midrangy amp with almost no clean range - and it made it really nice sounding - much fuller and clearer, and clean up to about 5 on the volume control, rather than 0.5 ;).

    Gain factor (not the only characteristic that matters, and very dependent on the circuit too, but a guide):

    12AU7 - 20
    12AY7 - 40
    12AT7 - 60
    12AX7 - 100

    (I'm not sure about the 5751, I think it's about 70).

    That's per triode, BTW - each tube contains two, and if they're used in series like most amps do, the result is squared, so there's a very big difference between a 12AU7 and a 12AX7.
     
  14. Marcello

    Marcello Member

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    cool report !

    I tried a mullard AT7 (CV4024) in V1, got less volume and drive, the amp was also much quieter...but i was missing the warmth of my JJs. I threw it in the PI and it's perfect ! i wasn't expecting a change but it's here, subtle of course.

    I'd go with a GE JAN 5751 to tame the drive now, that's how we learn.
     
  15. claptonisgood

    claptonisgood Member

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    i have been impressed with the new EH 12AY7...it has great tone in V1 of several amps i have put it in...more dynamic and better headroom than X's and it seems to have a fuller, more rounded sound which i am sure is partly due to the reduced gain...if you get a chance, pick one up...it may not be your cup-o-tea, but for about $10, it is an interesting tone machine to experiment with
     
  16. LHanson

    LHanson Member

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    P1?

    Is that the inverter?
     
  17. lanesmat

    lanesmat Member

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    I would suggest that anyone willing to experiment with preamp tubes to stop reading what is hyped and what sucks and let their ears tell them what to do.

    I'm not being a smartypants, but please bear with me. I was tube swapping on my Rivera Jake with the mindset of finding tone nirvana with all this aquired internet/expert/book knowledge. Rivera owner's forum, GP, GT, tube articles, Myles, studies, data, thesis, theorums, Scientific America, National Geographic, ad naseum, I was filled with knowledge and absolute truth...

    Needless to say (and I should have known better), I almost did not try my current tube combination because an AT7 is only a "utility" tube for PI's and reverb. Here is what GT says about it:

    Uh huh. Thanks for the tip GT.

    We should all have this mantra tatooed to our eyelids:

    It all depends on...
    Amp/guitar/pickups/speakers/effects/music style/volume/EQ/playing dynamics/room dynamics/etc... And the most important element - your taste.

    FWIW, I have a GE 12AT7 in V1, with Chinese and Rusky 12ax7's in the other tone V slots. A high gain preamp is not a be-all indicator for desirability and good tone IMO. It all depends, right? I had a couple of GTM's that had good gain and were not defective, but they fouled up my tone.

    [Off soap box]

    Scott L.
     
  18. Power Freak

    Power Freak Member

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    According to my datasheets that is correct. :)

    Before I modded the actual circuit on my DSL I did some tube changes, I put a Phillips 12AT7 in the PI which worked really well, reduced the "PI distortion" which I don't like very much. I also put a 5751 in V2 which made the amp clearer as a whole. IMO that's a great combo for a DSL, it clears it up just enough but still keeps its edginess.


    :BEER
     
  19. gkelm

    gkelm Supporting Member

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    I stumbled on this guy's site when doing some tube investigation a while back...

    http://www.audiotubes.com/12at7.htm

    You can click around and get good descriptions of various tubes & designations. I found it very helpful.

    Ended up ordering a handful...good tubes, service, and reasonable prices.
    Greg
     

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