12AU7 versus 12AT7 for reverb

Discussion in 'Glowing Bottle Tube Amp Forum' started by golfnut, May 13, 2021.

  1. golfnut

    golfnut Friend of Leo's

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    After having some issues with my 67 Fender Pro reverb lately its finally in tip top shape. I decided to completely retube it with fresh tubes. I ordered 4 12AX7 (Tung Sol) and 2 12AT7 (Jan Philips) as per the tube chart.
    When I took out all the preamp tubes I noticed V3 reverb send had a 12AU7. After getting the 12AT7 in there I noticed that the reverb was much stronger and where I normally had it on about 4 I had to turn it down to 2. I started reading that many prefer the 12AU7 as it gives more control over the reverb. I don't really notice "more control". Just stronger so you need to turn it down more for the same effect. I usually, mostly have reverb on very subtle, barely noticeable and will only occasionally turn it way up for a particular effect like Steel licks or other reasons for ambience. I like the 12AT7 and the fact their is more reverb on tap.
    Just wondering what others prefer.
     
  2. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    I like less reverb, and more control so a broader sweep across the dial works for me. I changed the return resistor on my most recent build to do just that. Now the surf happens at the end of the dial, not halfway up.
     
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  3. DADGAD

    DADGAD Friend of Leo's

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    I like a 12AU7 reverb driver in my 70's Twin Reverb. It tames it and a good vintage 12AU7 are dirt cheap.
     
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  4. theprofessor

    theprofessor Poster Extraordinaire

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    I have used both. I think my Princeton Reverb clone has a 12AU7 in there (maybe), while my Vibrolux Reverb clone has a 12AT7. As others have said, it is mostly about where the amount of reverb is on the dial, and also that 12AU7's are very, very cheap. BUT turning up the reverb dial also can mean more noise. So if a 12AT7 gets you the reverb you want even lower on the dial, it could be a bit less noisy. Of course there are always mil-spec versions of both the 12AT7 (6201) and the 12AU7 (5814A) that might make the noise issue less of a factor. But 12AT7's really aren't expensive, if you know where to look. Brent Jessee sells "butt ugly" RCA ones that are like new and at a good price.
     
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  5. Hey_you

    Hey_you Tele-Afflicted

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    I swapped to a AU7 also.
     
  6. muscmp

    muscmp Tele-Afflicted

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    i changed to a 12au7 also and like the expanded range.

    play music!
     
  7. Mexitele Blues

    Mexitele Blues Tele-Afflicted

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    I swapped to a 12AU7 in my '77 Pro Reverb for a more usable curve on the reverb knob, but I did not notice an appreciable difference.
     
  8. Willie Johnson

    Willie Johnson Tele-Afflicted

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    12AU7 in my PRRI reverb driver spot; way too splashy above 2 on the knob for my tastes without it. I turn it all the way to 10 for some things, and it sounds great.
     
  9. Sea Devil

    Sea Devil Friend of Leo's

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    I agree with the idea that a lower-gain tube has the potential to make end the signal noisier. More gain in early stages makes for a better signal-to-noise ratio, IMO, although I operated on exactly the opposite principle for years, trying for more headroom by using lower-output tubes in the pre-amp and reverb send.

    I think the takeup tube is the place to reduce "excessive" reverb (no such think in my book!) and cut noise. A good, low-noise 5751 in that spot can be exquisite.
     
  10. BobbyZ

    BobbyZ Doctor of Teleocity

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    Been using 12au7s for Fender reverb drivers for a long time, mostly because you get a lot of them in old organs. Having to turn up a bit more to get the same effect is really about all I've ever noticed.
     
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  11. Askwhy

    Askwhy Tele-Holic

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    Another big fan of the 12au7 for the driver. More usable range and also calms down the brightness a bit. A nicer, mellower reverb that just seems to sit better in the overall tone mix.
     
    Last edited: May 18, 2021
  12. Askwhy

    Askwhy Tele-Holic

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    You can use a 12dw7 there to tame just the reverb while keeping the gain intact. I had a clone where i had to use a 12au7 driver and 12dw7 recovery, you can do either one or both and see which sounds best. Cheap and reversible way to dramatically affect reverb.
     
  13. teleman1

    teleman1 Friend of Leo's

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    I'd like to smack the person who developed the 12au7a. Would it work in this application? Or only a 12au7?
     
  14. JeffBlue

    JeffBlue Tele-Afflicted

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    12AU7 in my reverb driver in my Fargen modded Bandmaster Reverb head. Sounds great to me.
     
  15. Paul G.

    Paul G. Friend of Leo's

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    No issue running two very different gains in parallel in the driver?
     
  16. NTC

    NTC Tele-Holic

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    Second that. The driver parallels the two triodes. That tube is really meant as a cathodyne pi (12au7 half) and the drive stage before it (12ax7 half).
     
  17. Andy B

    Andy B Friend of Leo's Silver Supporter

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    I use a 12AU7 in my 1970 Pro Reverb. Gives me what I want. In the 73 Bandmaster Reverb a 12AT7 is the ticket. Souinds much better than any 12AU7 I've tried. Runs cooler also.
     
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  18. Willie Johnson

    Willie Johnson Tele-Afflicted

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    Horses for courses. The 12au7 long plate I use in my PRRI does get pretty toasty.
     
  19. Askwhy

    Askwhy Tele-Holic

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    No, with the 12dw7, the 12au7 side affects only the reverb recovery and the 12ax7 side keeps the gain as intended. To be clear, the 12Au7 tube was in the reverb driver slot and the 12dw7 in the recovery slot. No issues, reverb tamed a ton and amp gain unaffected. Not sure if i understand the question though...
     
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