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ah, the joy of tubes!

Discussion in 'Amps and Cabs [BG]' started by nil, Dec 5, 2000.

  1. so with my ampeg b2r in the shop, i pull out an old Holden 200w tube head and plug it into the svt410hlf...sounds kinda like an old SVT head, maybe a little less presence, but hell, it's LOUD and sounds SWEET!

    so the predisposition i had towards valvies (reliability, re-tubing costs, fragility) started going out the door...

    ...and then a late 50's/early 60's Jansen Bassman 50 comes up for sale. (Jansen is a NZ company that made Fender-copy equipment back when, very Kiwi and now very sought-after)
    50w all tube head, in nice condition, but some nasty noise here and there (to be expected). i'm quite surprised at it power-wise - it was certainly loud enough (12o'clock on the volume was almost too loud) - and didn't break up too much.

    now i've grabbed some matched 6L6 tubes from a friend's Mesa Mark II head, along with the 12AX7s from it to try out. the Jansen runs 2 x 6L6s and 2 x 12AU7s, with no obvious bias control. here's the questions:

    - what is the difference between 6L6B's and 6L6G's?
    - i've thought of using 2 x KT88's from my Holden - i know they fit, but will they work without cooking, and will they sound much different?
    - benefits and drawbacks of substituting 12AX7s or 12AT7s in place of the 12AU7s in there (sound, reliability, etc-wise)?

    i popped in the replacement 6L6s and the 12AX7s this morning; it seemed to make it louder but it was hard to determine at the time - i just don't want to suck it and see and end up blowing things up if i've got it wrong!

    yes, it will be visiting a tech as soon as i can bear parting with it! :)
  2. b30307


    Nov 18, 2000
    About the tube #'s .
    The original 6L6 's had metal containers , ( pre modern guitar amps- before the 50's really ). The GC on 6L6GC
    means Glass Container, as in every 6L6 most players have ever seen . The modern GC tubes work better for
    music apps. , they're s'pose to be much less microphonic . So the GC thing is a hold-over from when both types were still made . Long ago . Now mostly people just say 6L6 . The 6L6 B is the latest updated version . I think it's also the premium tube # for companies like Groove Tubes .
  3. Please do yourself a favor and that little piece of tube amp history a favor and don't go futtin' about with something none of us are really sure about. It will be worth the time and effort to find someone who knows about those amps to check it out, and get the right parts and tubes to make it wonderful. There are a lot of things that you can do to that amp that are just too dangerous to try, dangerous to you because direct current kills and dangerous to the amp because you may cause irrepairable unreplaceable harm to that amp and it becomes a piece of JUNK.
  4. Thanks for the input people : finding people over here that speak the language is hard...

    bassbrad : thanks for the warning (and you do have a point), but the only way you learn more is by asking! :)
  5. b30307


    Nov 18, 2000
    Hey , I was just trying to provide a little info about one comment that was made . That is , what do the letters
    stand for . My info comes from Aspen Pittman , and it jives with everything else I've ever heard from people who actually work in the replacement tube business . I don't know if your kidding or serious , but you're incorrect - and I stand by what I said ,: GC stands for glass container ; period . Further , 5881's were
    heavy duty military/industrial versions of the 6L6 back in the day . The modern Russian version is softer , lower output , and not as sturdy . Then again , no modern tube is as well made as when they were standard
    consumer electronic items . Certainly no foreign company makes anything as good as GE ,RCA , Sylvania , or
    Tung-Sol made in the 50's, 60's , or 70's . Which is also why OEM US made tubes sell for 2 - 5 times what foreign
    tubes cost . If you can find them .
  6. Please do ask, and I apologize for going on a bit. Over the past 4 years I have been working at a repair shop and have seen some really foolish stuff that almost made me cry, I am not some vintage freak but I am someone who has a sense of history when it comes to gear and a love for it to keep on giving service making that most wonderful of sounds, music.

    Just this weekend a guy came in with a 64 fender twin, it blew a fuse, after it blew the spare some vacume head suggested putting aluminum foil around the fuse. The amp worked for about 1 minute and flamed up, chassis is ruined no way can it be rebuilt it's totally wasted, cabinet is ruined, the only thing salvagable were the speakers and one of them was blown. Those amps go for over a thousand dollars (us) and now a worthless pile of stinking waste.
  7. 6L6 was first, metal envelope, rated at like 350 V or so. I have some. Haven't even messed with them yet.

    Then came the 6L6G. "G" for GLASS envelope. Not guitar.

    Then came A, B and C variations each with better specs. GC does not mean Glass Container. Aspen was wrong. I thought that for years, too.

  8. I base my claim that the G stands for glass on nothing more than experience (5U4G to 5U4GB, 6N7 to 6N7-G, etc). I have no references. But I still don't believe you. :p (And do you blame me for not?)

    As a not-so-famous person on trial once said,
    "Everything you say is true, but I do not agree with it." :D


    As a tube head, you better know I'm messing with you in good fun.
  9. :D yay, my Jansen came back today. $200 later it sounds a million bucks, both channels work nicely, even the tone controls. Apparently it was a factory-experiment (they only made a few) back in '66/67 that turned the beast into a solid-state pre, tube power combo (i guess in order to maximise a cleaner sound).

    Pretty stupid really, so the repairman (who incidentally originally designed and built the amp!) made it all good. She's a hummer now! :D

    happy happy happy, tubes tubes tubes
  10. pkr2


    Apr 28, 2000
    coastal N.C.
    Psyco, You are dead wrong.

    The numbers on a U.S.A. tube use the standardized RETMA system.
    First#= filament voltage.

    Letter or letters= sequence. When single letters were used up, double letters were used.

    Additional letters, A= controlled fil. warmup time.//B= improvedperformance or rating// C= ditto, same as "a"// G= glass bulb.// GT= tubular glass bulb// W = ruggedized version // X = ceramic base // Y= phenolic base.

    To say that 6V6 tubes were ever used in a power supply borders on ridiculus. The letters after the filament voltage use "U" and "V" to designate a rectifier tube generally but not always.

    This did not come from a hobby catologue. It came from the RETMA standards. Plus over 30 years as a tech.

    the RETMA description of a 6SN7GT means a 6 volt heater or filament,7 elements(count the fil. as an element), tubular glass envelope.

    [/B][/QUOTE]6L6GB's are a step down in output from 6L6GC's. (The "G", BTW stands for "guitar" as in Fender guitar amps, the first guitar amps to make widespread use of them.)

    That one doesn't just border on ridiculus, it is ridiculus.

    You can't snow all the people all the time. :)


    [Edited by pkr2 on 12-21-2000 at 12:46 AM]
  11. pkr2


    Apr 28, 2000
    coastal N.C.
    I detect a little hostility here. I've not had time to post much, but I've been lurking here alot and I've seen some truly ridiculous things said about tubes here. Why haven't you come down on any of that?

    I don't even know you. How could I feel hostility for you? When you say things like"whoa,your wrong" and things like that, you're leaving the gate open to dissention.

    Where you are confusing the issue is using more than one standard to descrbe each tube. The RETMA is not the only standard system in use. The European standard is different from USA or RETMA standard but both are valuable sources of info at the design or replacement level.

  12. pkr2


    Apr 28, 2000
    coastal N.C.
    "Snow is it?"

    Sorry psyco, I missed this one. :)

    What i desribed as snow could be decribed as B.S., but I thought snow sounded nicer. :)
  13. pkr2


    Apr 28, 2000
    coastal N.C.
    For all the venom you used to discredit my posts, the fact remains that I didn't steer nil wrong. I answered the original question correctly. (Which I might add, you did not. You seem only interested in bashing me.) If you're going to help people and answer their questions, do that, but if you want to bash me, save the forum bandwidth and just do it via email.My address is publicly posted here.

    Psyco, it seems that you are the only one using venom. As I said, I don't even know you. Why would I have a beef with you?

    You are the one who set the tone of the discussion when you started the disagreement about the tube numbers with "NO! NO! NO! Way wrong!" That's really not the way to make a statement unless you are willing to accept disagreement when you are wrong.

    If you consider it bashing when I point out false information and back up what I say with my source of info, then if you continue to post erroneous information, I will continue to "bash" you. :)

    I'm sure that the moderator will let me know if I'm wasting too much bandwidth. I'm sure Paul appreciates your concern.:)

    BTW, I still can't imagine what kind of power supply used beam power pentodes, a tube developed for audio uses. Please enlighten me.
  14. nanook


    Feb 9, 2000
    You're back Psyco!

    Christmas in the shadow of Clinch Mountain?

  15. pkr2


    Apr 28, 2000
    coastal N.C.
    psyco, You just don't know when to quit, do you?

    I won't get into a mud slinging contest with you! If you would like to discuss ANY point that you choose from your last several posts, I will be more than glad to do so.

    I will, however, insist that the discussion be kept at an adult level and that we only discuss the technical aspects of the subject. You really, up to this point, have shown a short fuse when you feel that your expertise is being

    I very publicly apologize for my poor taste in my original response to your mistake. I also have to stand by the gist of my response.

    Maybe you've forgotten that a tube at its most base is a DC voltage amplifier. Take away the output transformer and you have an easily regulated DC power supply which can drive any number of things. Even today there are laser cutters which run off of tubes. Want proof? Howsabout this?:


    Thank you, I hadn't considered that as a use for a beam powered pentode. Just shows that I can be wrong. Big deal, I'm no less human than anyone else.

    I'll bet you that if you'll take the chip off your shoulder, you'll get more out of the discussion. :)

    My offer stands about the technical discussions. You obviously have a wealth of knowledge. Let's see how much mis-knowledge you might have.

    Before you are allowed to be the professor, you must show some credentials. O.K.?

    As judge Lane said,"bring it on". :):):)

    Merry Christmas man, ain't none of us mad at you. :)

  16. Hi Psycho, Hi pkr2, I love you guys. Way over my head, but I'm learning little by little. Can you recommend a good replacement mini-tube for my Eden preamp? Something warm, solid, and clear sounding. Merry X-Mas & Happy N.Y. Bob.
  17. pkr2


    Apr 28, 2000
    coastal N.C.
    Hi Bob, I'm glad someone is getting something useful out of this thread.:) :)

    My advice would be to leave the stock tubes in your preamp. A simple tube sub isn't going to make any dramatic changes in your tone. The characteristics of the stock tube were chosen by the circuit designer for reasons other than warmth, ambience and other purely subjective reasons. If the designer wanted a particular tone, you can bet your booty that he would have juggled the components of the circuits that are parts of the tone shaping circuits.

    Radio Shack, RCA, G.E., Radio Amateurs Handbook and Sylvania all have tube substitution charts that give the direct replacement subs. Stay with these subs and you aren't likely to do any damage. Just don't expect to see very much change.

    Bassbrad made an excellent point about the Fender that was butchered by well meaning people who really didn't intend to burn up a perfectly good amp.

    If one is smart enough to improve an existing amp with radical power supply and final modifications, they should be able to design an amp that has these changes incoporated to start with.

    An amplifier is very much like an automobile. If you take a brand new car and hop the stock motor up with high compression heads, radical cam and a supercharger, it will run much faster but it's not what you want for everyday transportation because each mod makes the car less reliable.

    I am certain that there isn't a member reading this that can listen to thier own tube amp and tell me what kind of tubes are in it strictly by the sound of the amp.

    There is also the resale value of a piece of gear to be considered. The resale value goes down in direct proportion to the well meaning mods that may have been done.

    Now I could start throwing around terms like plate load resistors, interelectrode capacitance and grid bias components to impress upon you how much I know and how little you know. That would not be any help as far as answering your question. Now if I were immature enough to think it somehow made me appear smarter I would consider doing just that. The truth of the matter is, I'm not that immature and it would only indicate that I am not intelligent enough to have a discussion at the laymans level.

    Hope this helps.

    Btw, merry xmas and a great new year to you too.:)


    [Edited by pkr2 on 12-26-2000 at 10:39 AM]
  18. Yyyyyyyyyaaaaaaaawwwwwwnnnnnn!!! C'mon guys, really!
  19. You boys sure are fun to watch. :D

    I do have to pipe up and say (i.e. fan the flames) that I own 2 old tube power supplies which use banks of beam tetrodes for output regulation. Neither one uses 6V6's. One has 6 807's, the other, which I cannabilized, had 6 Tung Sol 5881's (6L6WGB's). Each one voltage regulated 0-500V, at up to 500mA, with 10A 6.3V winding and 0- neg150 bias output. Kick axx to say the least. They both also use seperate rectifier tubes, each has a pair of big old 5RA4 (I think) funky looking big glass flat-top tubes with ceramic pedestal bases. The one that used 5881's fed the HV tranny with a variac on the 120V side for stage 1 voltage pre-regulation, and then out through the 5881's, all in parallel, for post regulation. There was a spring shaft from the variac rotor to a pot to make the 5881's stage track the variac stage. Neat, matter of fact, neater than most electronics today, although more rickety, and every moving part is a chance for failure. Both designs used a bunch of other small signal tubes and gas voltage regulator tubes, very pretty purple ones, I must say. :D.

    Purpose of post:
    Just making sure that everyone agrees that power supplies using some form of beam tetrodes (not necessarily 6V6, although they are a possibilty) as series-regulated DC output stages did and do exist. (Although staying high and dry up on the top of the proverbial fence. :D I ain't no troublemaker, sheesh.:p)

    Hell I can't even remember now if anyone's even arguing that.

    Yeah, you boys are alright. Holidays have got my panties in a wad as well.


    Once again, all in good fun, girls. Now, it's late, turn out the lights and no more talking or I'll make you sleep in different rooms. :D
  20. pkr2


    Apr 28, 2000
    coastal N.C.
    Darn it Chris , now you're attacking my character! :) :) :)

    Just kidding, chris. that's interesting and I concede the point. Heck, I concede all the points if I can remember what the points were.:) :)

    Psyco, I'm sorry that I hurt your feelings. I showed poor judgement in the way that I worded my original response. I'll meet you 2/3 of the way to make amends. I really didn't mean anything I've said as an attack on your character.

    Guys, I apologize to all of you for subjecting you to this squabble. As far as I'm concerned, it's over.

    Damn, psyco, that was hard to do. :):):)

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