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Tamed my Blues Deluxe with a 12AY7 tube

Discussion in 'Glowing Bottle Tube Amp Forum' started by Owensv, May 15, 2018.

  1. Owensv

    Owensv TDPRI Member

    45
    Dec 22, 2012
    Canton, OH
    In the for-what-it’s-worth department, I was about ready to chuck my Blues Deluxe. Not only was it unholy loud, it was just shrill and unmusical at times, with either ear piercing highs or a sloppy bass at volumes you would like to play. I toyed with the idea of a speaker swap, but after seeing many comments about changing the V1 position 12AX7 tube for a 12AY7, I spent the twenty bucks, and the amp instantly came to life for me. It is not just the more manageable volume control; it is the tone, which, on a Tele single coil neck pickup, is creamy smooth and like nothing I’ve heard out of my guitar before. All pickup positions are incredibly clear, and my added fourth position, which is a series combination, now sounds like a blues monster (before, it was sometimes a muddy mess). So, if there are any more BDRI owners out there who are less than thrilled, you might try this cheap upgrade.
     

  2. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Now, have the bias adjusted to a warmer plate dissipation and you will be further amazed.
     

  3. Dacious

    Dacious Poster Extraordinaire

    Mar 16, 2003
    Godzone
    The drive channel even becomes more usable. More Drive on the HRDx too. I think the reverb is better too. I suspect Fender copied a Bassman or Super for the main clean which were designed with a 12AY7 in the front slot.

    Of course, when released the 12AX7 and AT7 were the only new Noval preamp tubes available.

    There is one coupling cap on the main PCB that is a .047 - changing that to a .022 makes another difference.
     
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  4. Bob Sushko

    Bob Sushko TDPRI Member

    Age:
    57
    16
    Jun 10, 2017
    Alpine, NJ
    From the BillM website . . .

    The 12AY7 is also very similar to the 12AX7, but has less than half the gain. It’s the preamp tube that Fender used in classic amplifiers such as the Tweed Deluxe, many Champs, and the revered 57 Twin. Does half the gain mean half the volume? No. A Blues Junior with a 12AY7 in V1 will produce just as loud a clean tone as one with a 12AX7, but at 7 on the volume knob, while the 12AX7 will produce maximum clean at about 4. After that, the 12AX7 starts producing serious amounts of distortion. With the 12AY7, the onset is much more gradual.

    The 5751 or 12AY7 don’t give you any more clean headroom. They only delay the onset of distortion and limit the total amount of distortion
    _______________________________________

    . . . just throwing it out there
     
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  5. Ira7

    Ira7 Poster Extraordinaire

    Age:
    61
    Jan 8, 2008
    Coral Springs, FL
    I would have tested a 12AT7 first...worth the extra couple of bucks...but if the Y works, great!

    I gotta do a swap on my X2 head, but at only 15w, and with the pre-amp tube "just" used as a phase inverter, I don't know what to do.

    I demand clean as high up in vol as possible.
     
    Last edited: May 16, 2018

  6. Owensv

    Owensv TDPRI Member

    45
    Dec 22, 2012
    Canton, OH
    Excellent advice, thank you. Any pointers as to what should be the target? I’m plenty capable with the tools, but am not up to speed on biasing. I’ll poke around YouTube, too.
     

  7. Ebidis

    Ebidis Tele-Holic

    Age:
    51
    600
    Jun 27, 2016
    Alabama
    I did that with my Hotrod Deluxe, and it did make a difference.
     

  8. Mr. Lumbergh

    Mr. Lumbergh Poster Extraordinaire

    Jun 13, 2013
    Initech, Inc.
    What do you recommend there? My HRD is sitting right on 68mA, but I wouldn’t mind warming it up a bit.
     
    Last edited: May 16, 2018

  9. T Prior

    T Prior Poster Extraordinaire

    Mar 17, 2003
    Charlotte NC
    before changing or swapping preamp tubes we should check the 6L6 bias first, first things first. IF the bias is too hot or too cold this can make a noticeable difference in overall sound/performance. Changing a front end tube is not a bad thing but we may be trying to correct something that is caused by incorrect bias on the power tubes.

    Hot Rod Deluxe specs are 60 MV as the LOW to near 68 MV , or even a tad higher for the High.

    Blues Deluxe specs are the same, somewhere near 60MV as the low to 68 or even higher .

    Different power tubes or WORN/WEAK power tubes will react differently and will sound different.

    Before changing/swapping preamp tubes, check the BIAS first. Don't assume that the preamp tube will fix an issue , it may, or it may not. If the bias is wrong and we change a preamp tube, the bias is still wrong !

    Maybe the op can advise us on the age of his BD , there are other factors that can come into play regarding the scenario he is was describing.

    regardless, pulling the X7 to a lower gain tube can have merit.
     
    Last edited: May 17, 2018 at 4:14 AM
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  10. DaphneBlue

    DaphneBlue Tele-Meister

    Age:
    31
    234
    Jul 22, 2017
    Switzerland
    I've found this very cool video on youtube on the topic. Glad it changed you life with the Blues Deluxe!

     

  11. Commodore 64

    Commodore 64 Friend of Leo's Ad Free Member

    Age:
    42
    Mar 1, 2010
    Kent, OH
    What's your plate voltage? Is that for both tubes?

    450 Plate with .068A per tube = 30W cathode current per tube. That's nice and warm ( even -10% for screen current).
     

  12. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    I have never seen a Blues/Hot Rod Deluxe or Deville that ran warm plate dissipation at the factory settings. Usually one witnesses something around 32% of max plate dissipation.
    As Commodore notes, 68ma per tube is 100% of max plate dissipation. I have to think that that 68mv measurement is meant to be divided by two for 34ma per tube, which is about 50% of MPD. I have found that most of these amps dissipate in the low 50% range with the bias pot maxed out. I did see one last week that had a hot set of aftermarket tubes in it that maxed out at 62%.
     

  13. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    The 12AT/AU7 family of novals were designed as drivers. Note that Leo Fender in his day never used a 12AT7 anywhere but in the reverb driver and phase inverter(driver) positions. They handle the current differently than do the 12AX7/5751/12AU7 type of tubes. Both the 12AY7 and the 5751 change the way that first volume pot acts in the older Blues/Hot Rod acts. The 5751 is a higher gain tube than the 12AY7....AY has a gain factor 40 while the 5751 has a gain factor 60-70...AX = 100.

    X2....if there is a 12AX7 in that PI position, try a 12AT7. then try a 12AU7 type. Ime...and imho....if one wants higher volume cleans, one needs to buy a bigger amp. YMMV.
     

  14. archetype

    archetype Fiend of Leo's Ad Free Member

    Jun 4, 2005
    Williamsville NY
    In the SCX2 the 12*** is a dual triode: half driver and half phase inverter. A 12AT7 will provide the lowest gain and may sound exactly the way you want. That’s not an audio tube, though, and its effect at the driver stage may not be pleasing. Go downward in gain from the 12AX7. Try a 5751, then a 12AY7.
     
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  15. RCinMempho

    RCinMempho Tele-Afflicted

    Jul 8, 2003
    Maryville, TN
    12Ay7 in V1 really saved this amp for me a long time ago. I recently switched from an EHX to a JJ. The JJ seems a bit less brittle on the high end, but all tubes vary.

    After a long time, I switched the speaker to a Cannibus Rex. My ear piercing treble problems are all gone.
     

  16. Mr. Lumbergh

    Mr. Lumbergh Poster Extraordinaire

    Jun 13, 2013
    Initech, Inc.
    The CR really improved mine as well. Great speaker.
     

  17. JD0x0

    JD0x0 Poster Extraordinaire

    Age:
    28
    Feb 22, 2009
    New York
    FWIW the 12AY7 provides less gain than a 12AT7. 12AU7 would have the lowest gain, and best current driving properties
     

  18. archetype

    archetype Fiend of Leo's Ad Free Member

    Jun 4, 2005
    Williamsville NY
    Yes, thanks. You be right and I be rong.
     

  19. 410DeVille

    410DeVille Tele-Meister

    259
    May 26, 2012
    USA
    I didn't care for the 12AY7 in my BDRI. It sounded dull. Changing both V1 & V2 to 5751 sounds amazing to my ears.
     

  20. schmee

    schmee Tele-Afflicted

    Jun 2, 2003
    northwest
    A lot of people say a 12AT7 is not a "musical" tube. In my Carmen Ghia I ran the 12AT7 (where many run a 5751.. I think V2 IIRC) It was great, I liked it better than the other tubes the Z guys recommended. Somehow I think someone forgot to tell the electrons.
     

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