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Other than 12ax7's and 6L6's are there any other tubes used in bass/guitar amps?

Discussion in 'Amps and Cabs [BG]' started by Stinsok, Jun 29, 2020 at 6:05 PM.

  1. Stinsok

    Stinsok Supporting Member

    Dec 16, 2002
    Central Alabama
    While on vacation my wife and I stopped at an antique/flea market in Panama City, FL. There was one display that had a lot of RCA tubes in the box. No 12ax7/12au7/6L6. I'm guessing they were TV tubes. I was just curious if any of them could have been used for instrument amps.
    Last edited: Jun 29, 2020 at 6:19 PM
    HG1180 and lowendrachel like this.
  2. Loads. I'd say less 6L6GC than any of the other usual suspects. Have a look at a musical tube supplier website.
  3. Wasnex


    Dec 25, 2011
    12AX7, 12AT7, 12AU7, 12DW7 are all fairly common small signal tubes use in instrument amps. There are also several different names these tubes. For example ECC83, ECC803, 7025, 6681 are all 12AX7 equivalents.

    6L6 is a family of output tubes. Other common output tube types include EL34, EL84, KT88, and 6550.
  4. Stinsok

    Stinsok Supporting Member

    Dec 16, 2002
    Central Alabama
    None of those numbers were in there.
  5. Wasnex


    Dec 25, 2011
    ??? Okay I will me concise with my response: "12ax7/12au7/6L6" are all very common in instrument amps.

    As far as the other tube types I mentioned, you would need to know the different names they go under. Sorry but I am not going to provide a comprehensive list.
    mcnach likes this.
  6. Scoops

    Scoops Why do we use base 10 when we only have 8 fingers Supporting Member Commercial User

    Oct 22, 2013
    Sugar Creek, Wisc
    I am me
  7. Between Eurotubes and TheTubeDepot they should cover everything.
  8. As I always do I'll point out yet again that you will never find a 6L6 tube in a guitar or bass amp. The tube you could find is a 6L6GC. The letters are important as there are differing families of 6L6 variants.
    bobyoung53 and wcriley like this.
  9. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    FTFY. I have an Electar guitar amp (and the matching Electar lap steel) from roughly the late '30s or early '40s that has (IIRC) a pair of metal-case 6L6 output tubes ;)
    wcriley and agedhorse like this.
  10. Don't cloud the air with fluff. No amp built from the fifties do date use 6L6 tubes. :)
    Last edited: Jun 30, 2020 at 12:08 PM
  11. tonester


    Jun 1, 2009
    chicago il
    commercial user
  12. Edited to correct an omission.
  13. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    Ampeg also used 12DW7's in one stage of an SVT, and 7027's, another octal variant, as power tubes in some of their smaller amplifiers

    Older (1950's and before) amplifiers also used different tubes, of interest to collectors.

    And nobody has mentioned the rectifier tubes, most notably GZ34's and 5U4's.

    Another power tube that is biased like an EL34 is the 6CA7: it has the plates of a 6550, but is not as hard-edged on tone, and it has a little more headroom, but not quite the sparkle of a 6L6GT. The "big bottle" 6CA7 is my favorite power tube for the tone it makes.

    Another notable omission is the 12AY7, which Leo Fender used in the tweed amps for their sweet preamp tone.

    Many of these tubes have JAN numbers, but I can't remember the numbers. A good tube cross reference manual will have them listed.
    bucephylus likes this.
  14. when I find oddball tubes that have the same pinout as a preamp tube, I will swap that thing out and see what it does.
    Sometimes it does nothing, sometimes it changes things pretty drastic.
    I wouldn't do that with power tubes, but preamps and rectifiers, I swap that stuff out all the time and see what it does.
  15. Pilgrim

    Pilgrim Supporting Member

    Someone will correct me on this, but I thought that the suffix on 6L6GC tubes simply stood for "glass case." Otherwise, I thought all 6L6 tubes were electronically identical. I found a couple of info sources that provided more info; one essentially agrees with me, the other indicates that the C version tube may have more power handling capability. I surfed a couple of other sites which agreed that the GC version was a higher power handling tube than the GB type.

    All of the references I found agree that [6L6G] means 6L6, glass case.

    Evidently there were successive versions of the 6L6G with the glass tube becoming smaller over time. There is conflicting information over whether the "C" in GC stands for "compact glass tube" or "glass tube, electronic version C."

    I offer two sites with info, including links.......

    Here's some info from: Tube Information

    USA code: Codes consist of digits, letters, digits, possibly further letters.

    First digits give heater _voltage_ rating, with the exception that the codes 7 and 14 are
    used to indicate 6.3V and 12.6V valves with a locatal base.

    Letters specify the type of valve, but there appears to be no consitency of coding. S often
    indicates a single-ended (no top cap) version of an earlier valve with such a cap

    Second digits give either the number of active electrodes, or the number of external

    Final letters often specify the type of envelope. The code is
    G - large glass envelope.
    GC - Glass Compact - a tubular glass envelope
    GT - Glass Tubular - the smallest glass envelope
    M - Metal Envelope
    WA - High Quality version

    VT numbers are USA miliary valves. Unfortunately no way to decode.

    Here's an interesting discussion forum post from: 6L6 STR - GC etc. What's the difference ?

    All this applies to the large octal base tubes. When 6L6s and 6V6s first came out, they were in a metal envelope. When the first glass envelope versions were introduced, they had a G suffix applied (6V6G, 6L6G). These first glass versions used the large bulbous shouldered envelopes. Then they went to the smaller tubular straight sided glass bulb, a T suffix was added, hence the 6V6GT (glass, tubular). A later beefed up version came out, which was called the A revision, hence the 6V6GTA

    With the 6L6, they additionally did some internal mods to the guts to increase it's power handling, so the newly revised design became the A revision, so we had the 6L6GA. More revisions and beef-ups followed, giving us the 6L6GB and ultimately the 6L6GC.

    STR, depending on who you talk to, stands for "special tube request" or "special test request". Basically what this meant back in the day, is a large OEM customer would request the tube factory to test or tweak an current production tube for a specific operating condition or parameter. Like operating base-up in a high vibration environment, for example. Today, it's just more Mesa BS marketing. Mesa does not make tubes, they just buy them from the usual suspects and put their own labels and nomenclature on them. Mesa resells a couple three different versions of the current production 6L6, so they need a way to differentiate them from one another.

    EH means Electro Harmonix, one of Mike Matthews' companies. Marketing. His stuff comes from Russia.

    GTGE, etc whatever, is Groove Tubes marketing. They are selling a Chinese clone of some old GE designs. 6L6s and 6CA7s. Supposedly pretty good tubes but it's questionable if they are good enough to realistically justify the ultra high prices and marketing BS that Asspin lives by.

    So, a 5U4GBEH would be a 5U4, glass envelope and B revision, marketed by Electro Harmonix.

    The W suffix generally meant the tube was either a military version or had the base made out of a special low loss material. Mind you the low loss material only mattered at radio frequencies, and makes absolutely no difference at audio frequencies. A 6L6WGB would be a 6L6, glass and B electrical revision, with the low loss base. I'd rather use a 6L6GC any day. The original Tung-Sol 5881 fits into this category. It has basically 6L6GB electrical characteristics, but it's built like a tank.


    I would welcome a comment from @agedhorse on this, as I suspect he could resolve any confusion.
    jnewmark, RSBBass and Avigdor like this.
  16. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Thanks for those links.

    My understanding is that Mesa does more than "just buy them" - they also test the crap out of them, and reject any that don't meet their specs.
  17. 6L6WGB was an industrial variant and almost identical and interchangeable with the military 5881. It has less 'abilities' than the GC variant. it doesn't really matter what means what - they are just world games and are almost extinct. The point I was making was that the letters are important. The GB tubes will not last long in a modern tube amp.

    As for confusion you have added to it. If folk mean 6L6GC that should use the correct terminology or they could wind up with something different!
  18. Pilgrim

    Pilgrim Supporting Member

    I missed that in the section I copied and pasted. I have no reason to disagree with you.

    I draw the same conclusion you do about the 6L6GB tubes; they are evidently not designed for modern tube amp.

    I think the posts that I shared make it clear that there is still confusion around the terminology. I don't think I've added to that confusion, I think I've pointed out the lack of consistency.
    jnewmark and RSBBass like this.
  19. CosmicRay

    CosmicRay Supporting Member

    KT88 -I used them in my Sunn200S.
    dbase and Michedelic like this.
  20. devnulljp


    Oct 13, 2009
    BC, Canada
    Admin on the D*A*M Forum
    To be fair, you did say "never" -- I've had a few older amps with 6L6 tubes in them over the years too.

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