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School me on tubes..

Discussion in 'Glowing Bottle Tube Amp Forum' started by 4pickupguy, Oct 16, 2020.

  1. 4pickupguy

    4pickupguy Doctor of Teleocity

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    I have a 68’ Custom Deluxe Reverb. I want as much clean headroom as I can get. What’s best to achieve this? Is the first stage preamp the right place to start? Since there are only three manufacturers in the world, whose the best? Ones to avoid if any? Thanks!
     
  2. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    5751s will reduce gain. The modern Tung Sols are pretty good.
     
  3. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Regardless of the preamp tube you put in, the amp will make about 22 clean watts before it breaks up.

    Some people use the term "headroom" to refer to how far they can turn the volume knob before it breaks up, but that's not correct use of the term.
     
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  4. schmee

    schmee Doctor of Teleocity

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    I have gigged a DR for 40 years rarely above 3 on the volume.

    There are two brands of pre tubes I would avoid for clean: JJ and Penta. The JJ may have just been a couple bad ones I got years ago though.
    Many relabeled 12AX7's are Shuguang/Penta, they are the worst. They are often in new amps due to their low cost to the maker. You can ID them by a silver plate inside the tube that wraps about half way around. Seen here: https://www.ebay.com/c/1227615316

    My favorite modern 12AX7 is the Mullard RI.
    The '68 CDR is not noted for the clean headroom the 65RI is.

    My advice overall is :
    JJ 6V6 power tubes
    Mullard RI 12AX7's in V1 , V2 and V5
    For the Reverb tubes, V3 and V4, just use what you have.
    NOS 12AT7 are available at reasonable cost for the phase invertor V6
    Bias the 6V6's for clean.

    Speaker: one of the most important things for a good clean loud DR. What one do you have?
     
    Last edited: Oct 16, 2020
  5. loopfinding

    loopfinding Tele-Afflicted

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    -JJ 6V6S have a larger plate and max 14W dissipation over a usual 6v6 @ 12W. you might be able to squeeze a little more headroom out of them.
    -use a higher sensitivity speaker than the jensen, like an eminence legend 1258.
    -you could try a 40W OT provided you match the impedances, like a bandmaster

    the first two are the least hassle and will probably get you want you want.
     
  6. Chiogtr4x

    Chiogtr4x Poster Extraordinaire

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    When I owned my original '68 Deluxe Reverb, which I wanted ( to our amp tech buddy Pete Cage) 'big and clean, please..'

    So it was JJ 6V6's for power, maybe TAD or Tung-Sol 12AX7s ( for gain) and I already had an Eminence Red, White, and Blues speaker in there ( 120 watts).

    I ran it at about 4-5 which was plenty loud ( and clean) and used a Tube Screamer type or Barber Direct Drive ( and moderate Drive) for OD

    * what a wonderful amp!
     
  7. TheDams

    TheDams Tele-Holic

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    More than the (very few) differences between the actual manufacturers (Saratov, JJ, Shuguang), I'd pay attention to the places selling the tubes... how do they select them, sort them, pair them, etc.
     
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  8. MilwMark

    MilwMark Doctor of Teleocity Ad Free Member

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    Buy a Vibrolux?

    But if you insist on keeping that amp, different brands of tubes are not going to change much. You could mod it a la Pete Anderson to take 6L6 but that is very extensive (see Vibrolux, above).

    With that amp, a cleaner, more efficient speaker is the way to get more headroom and volume. Celestion rates the V type around 98 db. Some Eminence speakers are rated 102-103 dB sensitivity. That 5-6 dB efficiency increase creates a MASSIVE volume/headroom increase.

    I don't know why you'd pick a DR (let alone one modded to have LESS headroom) if your goal is clean headroom. But putting that aside, speaker sensitivity (not tube brand) is the tree to bark up to get there.

    @Wally or @muchxs or others probably have more coherent and cogent thoughts on this though.
     
  9. JRapp

    JRapp Tele-Holic

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    That amp has been modded to break up sooner. Restore the NFB circuit to stock values. Then get an EVM 12L. You can also stuff some 6L6GC/5881 in it---that's the old hillbilly fix; no more wattage, but it seems like more headroom.
     
    Last edited: Oct 16, 2020
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  10. Askwhy

    Askwhy Tele-Meister

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    A more sensitive speaker will make far (and i mean faaaar) more difference in how loud the amp gets before breaking up than tube choice. Guys like the Cannabis Rex for that purpose.
     
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  11. 4pickupguy

    4pickupguy Doctor of Teleocity

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    I’m not trying to get “more wattage” out of my Deluxe, just trying to keep as loud and clean as is possible from all of it’s mighty 22 watts. I really didn’t spell that out in the OP. It’s been a minute since I’ve bought any tubes, in fact, last time I did, they said Western Electric on them...
     
  12. jimgchord

    jimgchord Tele-Afflicted

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    You wont get headroom from tubes. Try a more efficient speaker.
     
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  13. hepular

    hepular Tele-Holic

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    just to be clear, i'd look for nos 5751s for v1 . ..
     
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  14. nedorama

    nedorama Tele-Meister

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    Hate to say this, but you bought the wrong amp... for more headroom, you'd be happier with a Deluxe Reverb Reissue. this version of the Deluxe Reverb has lower headroom and wants to breakup earlier.

    If returning the amp and getting a DRRI isn't an option:
    • Fix the reduced negative feedback that's built into your model.
    • Swap out the Celestion G12V-70 speaker for a higher-rated Weber or Warehouse Guitar model.
    • If you're still looking for more clean, then think about changing the tubes.
     
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  15. MuddyWolf

    MuddyWolf Tele-Meister

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    Put in an evm12l. Or maybe a JBL. Nothing else is going to work.
     
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  16. avspecialist

    avspecialist Tele-Meister

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    4pickupguy, from what I read, you could start with the power tubes. You can call The Tube Store toll free in Canada and tell them what you are trying to accomplish. You should be able to get tubes from them that are tested and matched for less breakup. Also I really like their Preferred Series 7025 tubes. The have good gain and not as much over saturation for V1 from my trials against other brands. With the power tubes, they must be biased properly in order for the to react best in your amp. Some people just use a meter and calculate numbers. For me I do that but also look at the output on a scope to determine my final bias. Other tubes I like are the tungsol, EH and the CV4004 reissue Mullard.
     
  17. Geo

    Geo Friend of Leo's

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    I get good variation of sound characteristic with different brands of 12AX7. Then there are the 12AT7s and 5751 variations. The power tubes of course need to be good as well.
     
  18. Paul G.

    Paul G. Friend of Leo's

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    Your amp was designed to "break up".

    It does.

    Everybody says that's what they want.

    It isn't.
     
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  19. 4pickupguy

    4pickupguy Doctor of Teleocity

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    ...or post #12. Like I said, thrilled with the amp. Just trying maintain its 22watts.
    Thanks for the help!
     
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