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Preamp Tube Advice

Discussion in 'Amps and Cabs [BG]' started by jaeman111, Mar 21, 2006.


  1. I have a Demeter VTBP-201s which I really like, but I think it has a bad tube. It sounds slightly microphonic, but only at certain frequencies. It seems to improve after being left on for a while. I'm not sure if this normal or not, but I was wondering if anyone has recommendations for easily found replacements. I would be interested in suggestions for a 5751as well as the stock 12AX7. I like clean articulate punch, but I do not like overly bright click and clack.

    Thanks,

    Jay
     
  2. I like the ECC83. It's the European version of the 12ax7. It has a more linear or true tone to it. I was first turned on to them when I noticed they came stock in my Eden WT-400 I bought a few years back.

    A good way to test your tubes is to hook up the pre to an amp and speakers, at low volume. Turn down the input gain all the way, then turn up the volume. A small bit of noise is normal, excessive noise is not, and means the tube is going bad. Then take the rubber end of a pencil and tap the glass of the tube gently. If you hear nothing or a short click, that's good. If the tubes makes a ringing sound, then it is microphonic, and should be replaced. I saved a guy a lot of money last year by doing this and finding it was a single microphonic tube in his Marshall amp that was bad, so he didnt have to replace all of them.

    Hope this helps
     
  3. Thanks for the tip Shoreline, does anyone else have more tube recommendations? I might just end up buying a couple of each and trying them all out. Thanks, TB'ers...
     
  4. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Tube recommendation...JJ ECC83. After trying out several in my SWR amps, I've found these have the best of all of what I'm looking for. In comparison, I found a Sovtek 12AX7 (not sure which model, but more than one tube) to sound thin and introduce some hum.

    I just bought four of the JJ tubes from Vintage Electron on eBay as white box unlabeled tubes for $5 each plus shipping. These tubes are distinctive looking enough that I'm sure they sent what was promised.
     
  5. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
  6. I always go with the GT ECC83 from Groove tubes. It is a JJ Tesla ECC83, but the Gt testing is second to none. They actully reject more than they use. And they have great low end response. They are about $20, but well worth it.
     
  7. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
  8. Please don't perpetuate this myth. I deal EXTENSIVELY in tubes, and GT has far greater failure rates than other brands, especially for their ridiculous prices. If you want a JJ 12AX7 (a great tube, BTW) get it from JJ Electronics. Their distributor is Bob Pletka at www.eurotubes.com . BTW, there is NO difference between a "12AX7" and an "ECC83." Both mean exactly the same thing. One is simply the European designation and the other American.
     
  9. Dittto.
     
  10. westland

    westland

    Oct 8, 2004
    Hong Kong

    +1

    JJ, Tung-sol, EH are the best of the 12ax7s, go with JAN GE on the 5751 for a warm sound.

    GT is overpriced, and so so, very much like the stock Shauguang Chinese tubes (in fact they might just be relabeled)
     
  11. JAN GE 7025 tubes, JJ ECC83's, JAN Philips 5751, JAN Philips 12AT7 to name the ones I'm settling on the more I test them all out. 5751 tube has slightly less gain than the 12AX7 types (7025/ECC83/12AX7) - 12AT7 even less. I find that sometimes a 5751 or 12AT7 works a bit better for bass depending on the circuit and desired tone.

    Psychobassguy can give you all the actual Mu ratings as well as explain the way the industry is "put together" right now.

    For bass I would avoid the new JJ ECC 803S long plates...a better tube for guitar in my opinion. I wrote a review on this tube in a thread about a week ago.

    Jay
     
  12. bucephylus

    bucephylus Supporting Member Commercial User

    Aug 18, 2002
    General Manager TecPadz LLC
    Here's a site I referred to when I was looking:

    http://www.audioasylum.com/audio/faq/joes-tubes.html

    You might find some interesting reading there.

    I bought some of the Sylvania 5751 Gold Pins when you could get them, and they work quite well. At some point, it becomes kind of like wine tasting as to what you like better. Then you forget about it and just get on with the playing.
     
  13. Th guy who wrote that needs a hobby, and remember he's applying audiophool standards (hopelessly vague terminology, wine tasting analogies, etc) to an electrical item. There ARE concrete techincal terms to describe the tonal properties of tubes, but this guy is so enamored with his own listening skill, I doubt he's aware of them. I'd avoid that site for anything other than just familiarization with the number of differing vintage makes. Technically, it's useless.
     

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