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Tube Questions

Discussion in 'Amp Central Station' started by Norton72, Aug 2, 2013.

  1. Norton72

    Norton72 Tele-Afflicted

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    Don't know if this is best posted here or at the Glowing Bottle forum...

    I got my new Excelsior yesterday via FedEx as can be seen here. There is a noticeable hum and I thought this might be caused by the tubes as I have seen on here before. Is the hum typically caused by preamp tubes or power tubes? I have some preamp tubes on hand, a pair of Sovtek 12AX7WA's and a pair of Audio Glassic 12AX7A's. I have been looking at 6V6GT's on Ebay, and this leads me to another question:

    Many pairs of tubes on Ebay advertise to be "matched", but I have read an opinion that testing for mutual transconductance is not sufficient for guitar amps and they went on to explain in detail their method. Not knowing much about tubes, this bit of information has only served to confuse me more.

    I have been looking at NOS and used RCA blackplate 6V6GT's primarily, as well as some Sylvania JAN and RCA JAN tubes. Any thought on this? It is my understanding that all new tubes are now manufactured in one of four facilities, two in Russia, one in China and one in Slovakia. I'm sure they are made to the particular specs of the "brand", but I wonder about consistent quality.

    Oh, and how are the metal envelope tubes suited for guitar amps? (6V6)
     
  2. Camplain

    Camplain Tele-Holic

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    I can comment on the ebay thing... I bought a pair of not NOS but lightly used old "matched" 6v6s several months ago. When I popped them in the amp there was a 7 or 8mA difference on my bias probe... I contacted the seller and they fed me some line about tubes responding differently in a guitar amp than on a tester... I really don't know much about the technical side of it, but apparently "matched" doesn't mean much in some cases... I'd be cautious.
     
  3. alnicopu

    alnicopu Friend of Leo's

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    I bought a set if RCA labeled grey bottles on eBay that were matched within 1ma. I've posted this before but I bought a set of NOS JAN 6v6s from tube depot. A few months layer I read somewhere that they tend to develop rattles more than other NOS tubes. Low and behold, about a week after reading that, one started rattling like crazy in my Princeton reverb. It was unusable so I stuck the good one in my champ and have had no problems. That was about a year or so ago. When I got them they were 40.00 per set now their like 90.00. If it were me, at that price and with the experience I had I'd not risk the Jan 6v6.
     
  4. 410DeVille

    410DeVille Tele-Meister

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    NOS tubes in a $300 amp, seriously?

    Personally I would never buy tubes on fleabay. I would get them from a reputable tube dealer. You're less likely to have problems. I've had good luck with Tube Depot and Amplified Parts.

    For 6V6 I would get current production Tung-Sol or Tube Amp Doctor.
     
  5. muchxs

    muchxs Doctor of Teleocity

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    "Reputable dealers" need to buy in bulk and maintain inventory. The problem with that is the only tubes available in quantity are new production.

    Don't think "reputable dealers" spend a lot of time testing their tubes. They don't.

    I buy tubes on eBay all the time. I especially look for tubes that are likely to be matched. No big deal if they're not. I use the "orphan" tubes in single ended amps.

    I get a ton of great tubes. Mullards. Telefunkens. The trick is to let the audiophiles have the "investment grade" tubes. I only want the ones that sound good.
     
  6. Norton72

    Norton72 Tele-Afflicted

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    Seriously -- they can be had for $20-$40 a set. Cheaper than new.

    OK, mostly used at that price, my mistake. When I see a seller with 20K+ transactions and 99.9% positive feedback, I gotta take a chance on that.
     
    Last edited: Aug 2, 2013
  7. printer2

    printer2 Poster Extraordinaire

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    I need to find some audiophiles. Just found these in a piece of gently used test equipment.

    [​IMG]


    Oh, you caught up with me in the other forum. Damn it, too many forums!
     
  8. Norton72

    Norton72 Tele-Afflicted

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    Meh, I'm an idiot anyway. Got home from work today and realized that the hum is only present when the volume on the guitar is turned up. with the guitar turned down, there is a slight hiss beginning at about 10:00 on the Bright setting and about 2:00 on the Dark setting.
     
  9. Norton72

    Norton72 Tele-Afflicted

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    Of the 12AX7's I have on hand, the Sovtek wins. Actually I had three Sovteks and on Audio Glassic, not two and two as stated earlier. I'm not sure how the AG got in the mix, but when I bought my Crate VC5310 in 1994 it came with four Sovtek 12AX7WA's and four Sovtek EL84's. I went away in 1996 and didn't touch the amp again until 2003 at which time I immediately changed all tubes out for Groove Tubes. So I've had these tubes for almost 20 years and they've been played for about two. I gigged every weekend for about a year of that time.

    Don't know what I'll do with the EL84's, just hold on to them I guess like I do everything else.
     
  10. Boogie

    Boogie Tele-Meister

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    If a tube amp isn't making 'some' extraneous noise, it usually means one of two things: 1) It's not turned on, or 2) You blew it up. ;)
     
  11. Teletubbi

    Teletubbi Tele-Holic

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    glad you figured it out, with a few hours getting to know it it should sound a lot better:lol:
     
  12. BiggerJohn

    BiggerJohn Friend of Leo's

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    All the Audio Glassic tubes I've seen are just re-labelled Chinese.
     
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