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  • Tube Questions

    I'm going through and changing out all the tubes in my VT-120, it is the first time I am doing this. On the back of the amp it shows the tube layout (4) 6L6GC, (4) 12AX7, (1) 12AU7. I am familiar with the 12AX7s. Can I relpaace the 6L6s with any type, or do they have to be "GC". Also the 12AU7, what is that for, I've never heard of it before.

    What do you guys like in Groove Tubes for a decent amount of gain. I was thinking of going with 3s.

    Thanks.

  • #2
    Re: Tube Questions

    I might be wrong, but I think 6L6GC refers to all 6L6 tubes?? And I believe 12AU7 is the rectifier tube. Apparently all tube amps have a rectifier, but Mesa did something special or just marketed it differently or something like that.
    EBMM JPX BFR (Crunch Lab/Liquifire)
    Schecter C-1 Classic (Custom8/Jazz)
    Mayones Duvell 7 Standard (Instrumental SFTY-3/Decomp)
    G&L Tribute Comanche
    Godin Stadium 59 (Custom Cajun/'59)
    Horizon Precision Drive --> Fulltone FB3/FD 2 --> Crybaby From Hell (Fasel) --> Boss BF-2 --> CH-1 --> TC Flashback X4
    Mesa/Boogie Mark IV-B (SED =C= 6L6) + EarCandy BuzzBomb 2x12 (V30/C90)

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    • #3
      Re: Tube Questions

      Musician's Friend says the 12AU7 is a "phase inverter". I am not sure what that means.

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      • #4
        Re: Tube Questions

        I've been duped again
        EBMM JPX BFR (Crunch Lab/Liquifire)
        Schecter C-1 Classic (Custom8/Jazz)
        Mayones Duvell 7 Standard (Instrumental SFTY-3/Decomp)
        G&L Tribute Comanche
        Godin Stadium 59 (Custom Cajun/'59)
        Horizon Precision Drive --> Fulltone FB3/FD 2 --> Crybaby From Hell (Fasel) --> Boss BF-2 --> CH-1 --> TC Flashback X4
        Mesa/Boogie Mark IV-B (SED =C= 6L6) + EarCandy BuzzBomb 2x12 (V30/C90)

        Comment


        • #5
          Re: Tube Questions

          that 12au7 is another preamp tube... from what i understand it is a 12ax7 with much less gain. also used for driving reverb i believe.

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          • #6
            Re: Tube Questions

            This is from Justin Holton's Unofficial Fender Hot Rod Deluxe Owner's Guide:

            How are tubes named?
            In the United States vacuum tubes are identified by a naming system that is fairly standard.

            1. The first part of a tube designation is a number (or numbers) which tells us the approximate voltage required for the filament of the tube. For example, the filament of a 6J5 requires 6.3 volts, the filament of a 5U4 requires 5 volts, and the filament of a 50L6 requires 50 volts. 12AX7s require 12.6 volts when wired in series, but when wired in parallel, as in almost all musicial instrument amplifiers, they require 6.3 volts. It's no coincidence that the 6L6-GC requires 6.3 volts, this allows us to hook them to the same voltage source.

            2. The second part of a tube designation is a code letter (or group of letters) for identifying the tube types and functions.

            3. The third part of a tube designation is a number which sometimes indicates the number of useful elements brought out to the base terminals. For example, a 12AX7 has seven elements if we consider the filaments (pins 4, 5, and 9) as one element.

            4. The fourth part of a tube designation, if included, will consist of a letter or letters describing some particular characteristic of the tube. For example, a 5Y3-G has a glass (G) envelope. A 5Y3-GT is the same as the 5Y3-G except it's glass envelope is smaller (GT) than that of the G.

            It must be emphasized that the following descriptions are generalized, and that there are many exceptions to what's listed here. Also note that Europeans use a different naming system. The only method of retrieving accurate information about a tube is to refer to its spec sheets.

            Power tubes you should NOT use:

            The 6L6 and 6L6GC are not the same tube!
            Any power tube advertised as a 6L6, 6L6G, 6L6GA, or 6L6GB. Generically, 6L6GCs are usually referred to as "6L6s." Technically, these are NOT the same tubes! In fact, they are very different from each other! If you direct your attention directly to the right you'll see blatant proof of this: a comparison of a RCA 6L6 with a RCA 6L6GC. Take note that the differences are far more than just superficial, as I'll soon show. So why do techs and tube dealers refer to 6L6GCs as 6L6s on message boards? Laziness. I guess it's just much easier on the fingers to not include that extra "GC." I, on the other hand, will be very specific on this website and on the internet forums that I frequent. You should be too, as being ambiguous only adds to the confusion that plagues most discussion boards.

            The Hot Rod amps have a plate voltage of around 430V (Deluxe) or 475V (Deville). They were designed to be used with 6L6GC tubes, which can handle 500 volts/30 watts on the plates, and 450 volts/5 watts on the screen. Lets take a look at the other 6L6 variations and see exactly how they differ.
            ~Sid

            "If you play a Nickelback song backwards you'll hear messages from the devil. Even worse, if you play it forward you'll hear Nickelback." ~David Grohl

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            • #7
              Re: Tube Questions

              6L6 This is the original version placed inside a metal envelope (pictured above on the left). It can handle 360 volts/19 watts on the plates, and 270 volts/2.5 watts on the screen.

              6L6G This tube has the same specs as the 6L6, but is placed in a large "Coke Bottle" shaped glass envelope?which is what the "G" stands for.

              6L6GA This tube is the same as the 6L6/6L6G, though is in a smaller "Coke Bottle" shaped glass envelope. The Groove Tube 6L6-CB, the CB meaning "Coke Bottle," is probably the Chinese remake of this tube.

              6L6GB Also has the same specs as the 6L6/6L6G/6L6GA tubes, except its envelope is straight sided glass like the 6L6GC. So visually this tube and the 6L6GC look alike, but internally are completely different.

              5932/6L6WGA This is a mechanically rugged-ized version with a huge brown base and straight sided glass envelope similar to the 6L6GB/6L6GC?it was produced only by Sylvania. It's electrical specs are exactly the same as the 6L6/6L6G/6L6GA/6L6GB.

              Groove Tubes 6L6B Practically every time I get an email from someone complaining about how their amp crapped out on them (usually lost almost all its volume), they always mention that their amp worked fine before they installed the GT 6L6B. What makes this one especially scary is that putting in the old tubes did not fix the problem! Do not use this tube; after all the emails I've received I can only determine that this one is an amp killer. All I know about it is that the "typical power ranges from 20 to 25 watts," which couldn't be more ambiguous. So stay away! I can no longer find this tube on Groove Tubes' website, which means they either renamed it or scrapped it altogether?hopefully the latter. And to think that "the 6L6B is perhaps the most reliable of the currently made types of 6L6s." (Groove Tubes quote) Yikes!

              If you use any of these tubes, do not be surprised if the tubes go and the amp goes with them.
              ~Sid

              "If you play a Nickelback song backwards you'll hear messages from the devil. Even worse, if you play it forward you'll hear Nickelback." ~David Grohl

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              • #8
                Re: Tube Questions

                As you can see the the 6L6 and 6L6GC are different tubes!
                ~Sid

                "If you play a Nickelback song backwards you'll hear messages from the devil. Even worse, if you play it forward you'll hear Nickelback." ~David Grohl

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                • #9
                  Re: Tube Questions

                  thanks tgs, that really is nice to know about. i assume this goes for all kinds of tubes too
                  Cleveland Guitars

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                  • #10
                    Re: Tube Questions

                    Check out this link for other info on tube gain factor - the rest of the site is also quite informative and offers good prices on all kinds of tubes for guitar amps: http://store.yahoo.com/thetubestore/gainfactor.html

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