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Bassman 100 tube swap kt66

Discussion in 'Amps and Cabs [BG]' started by top028, Nov 6, 2013.


  1. top028

    top028

    Dec 14, 1999
    Lancaster, PA
    I need new power tubes. Very disappointed by the longevity of my last set; newer sylvania 6l6GC and I paid for them too. I am not sure of a real decent 6l6GC, I have been mislead with voodoo before. I felt like my last set of JJ were ok, but that 4 years ago when I bought them they lasted a long time, but the low end didn't feel quite as tight. SO...

    KT66 look badass. Heater current is 1.27 leaving me feel safe, since I found this great site...http://www.el34world.com/Transformers/fentrans.htm
    022756 is stamped in my pan.

    Vg2 max is only 400, but I am pretty sure the schematic reads 375 volts. Should I go for it? Seems safe enough.
    I recall some one making an almost 6550 with reduced heater current. I cant find it now though. Has anyone real-life tried this, who runs their amp wide open all the time?
     
  2. edwinhurwitz

    edwinhurwitz Supporting Member

    May 13, 2003
    Boulder, CO
    Endorsing Artist: DR Strings, SMS
    I haven't tried this, but I have a friend with a Twin with KT66s that sounds pretty good. My favorite tube is the Philips 7581A. They are getting pricey, but they have a MTBF of 5000 hours. The last set of tubes I got were 6L6GC STR-387s from Fat Willie aka Lord Valve. They are fairly similar to the 7581s. He has pulls for a pretty decent price.

    I'm tempted to try the current production 7581As. They are much cheaper than NOS and some of the reports are pretty good. But, at this point I am set for quite a while, what with a quad of 7581As for my MC30s in my home stereo and another in my Showman.
     
  3. The problem with buying NOS tubes is you can not be sure the "N" (for new) is true, they could just be Old Stock that looks new ;).
     
  4. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    New production KT66 aren't too good, spoke to their tech had trouble getting reliable ones for Marshall Vintage Moderns when Killing Joke used them, so they went to Framus with KT77.
     
  5. edwinhurwitz

    edwinhurwitz Supporting Member

    May 13, 2003
    Boulder, CO
    Endorsing Artist: DR Strings, SMS
    Absolutely. That's why I buy from Fat Willie. Whatever you think of his politics or anything else, the guy is straight up when it comes to his tubes (and his amps for that matter. His newest creation looks like a Fender if it were made in the old Hiwatt factory. Impeccable layout).
     
  6. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Ha, was talking to a dude who used to drive bands down there to collect their amps, was literally the garage on the side of the guys house.
     
  7. I've been using sovtek 6l6wxt+s in my 100 watter from 71 and they seem to take the beating better than most other 6l6s other than the old svetlanas.
     
  8. Not impuning "Fat Willie" (I bet that reads badly across the pond) whoever he is. His info will only be as good as the info given to him unless he buys only from government military surplus lot sales.
     
  9. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Way i see it, if someone buys them, they ain't new. If someone runs them through a tester, they definitely aren't new, because that is using them. I'll take tested over 'NOS' any day, and people who claim both at once about a valve are not to be trusted.
     
  10. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    I have had great luck with fat Willie aka Lord Valve. That said, about the best 6l6 going is the Winged C. I have a pair in my Music Man RD-100. They sound great and stand up to a circuit that pulls 100 clean watts from a pair of 6L6's. The Winged C's I got from Tube Depot.

    Lord Valve is the guy I call when I want to retube an amp ground up and hve specific tonal/ breakup goals in mind. I have done a few old vintage amps with him. Never been disappointed. He's quirky but then again so are we all...
     
  11. edwinhurwitz

    edwinhurwitz Supporting Member

    May 13, 2003
    Boulder, CO
    Endorsing Artist: DR Strings, SMS
    Well, aside from being a B3 player, Fat Willie (aka Lord Valve) learned his tube craft from the US military (Navy guy in the 60s). He gets tubes from all kinds of places and has about 30 or 40 old tube amps (mostly PA heads) that he uses to burn them in and then a ton of high tech test equipment. His info comes from his own two hands, his own two eyes and his extremely conservative noggin. It's not rocket science, but it is science. He's a character, for sure*, but he knows tubes as well as anyone on the planet. Apparently he's a hell of a B3 jazzer, but I haven't had the pleasure of hearing him play yet.

    But, I share your skepticism in general. If I hadn't been buying tubes and getting amp rebuild pointers from him for close to 20 years, during which time I learned his history and saw his test equipment in action, I wouldn't have the faith in him that I do. My experience with him is what keeps me from trusting most of the online shops.


    * for entertainment, you can look up Lord Valve on rec.music.makers.guitar.jazz or alt.guitar.amps on usenet. Some of it is not very pretty and there are those who won't buy tubes from him out of political principle. To be fair, he did kick a friend of mine out of his shop for similar reasons. He's worth a visit if you do go to Denver for any reason.
     
  12. wmheilma

    wmheilma

    Jan 5, 2010
    On the subject of Fat Willie... I had him re-tube my amp and got ten years of moderate use from a set of Sovtek 6550's. So I don't care of he charges a bit more. I got more than my moneys worth especially after hearing other folks tell me those had a high failure rate when they got them of the shelf. So I had him work on my amp again and it sounds great with Tung Sol 6550s now :)
     
  13. top028

    top028

    Dec 14, 1999
    Lancaster, PA
    So, I take it the extra expense of a KT66 is waste. I will look at the different GC offerings. Tungsol looks cool, maybe I will try the JJs again.
     
  14. Changing to a differing tube type one should consider several characteristics. Heater current draw is one. Changing to a KT66 adds 0.37A per tube to the heater draw. That's another 1.4 amps above what the PT was designed for. In an amp that was built towards the lowest price this could well be too much.
     

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