Tube Tester Suggestions?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Plexed, Feb 11, 2005.

  1. Plexed

    Plexed Member

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    I am looking for an inexpensive tube tester, that is easy to use for pre/power tubes for guitar amps. I see a bunch of these things on ebay but many seem way over the top with knobs & dials. Any suggestions for a basic model that a newbie could understand? Thanks very much!!


    Plexed
     
  2. John Phillips

    John Phillips Member

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    This probably won't help much if you're just starting out... but then neither will a tube tester really.

    What I would do is get hold of an old cheap amp - something like an old tube PA head, or an amp that's been so hacked it isn't really worth anything.

    You will probably need to modify it depending on what power tubes it's wired for - ground pin 1 for EL34s, widen the range of the bias supply, for example - and you may need to bring down the HT voltage for testing 6V6s, if it isn't low enough anyway. You may also need to beef up some other components (eg screen resistors) or fit more fusing to stop it going up in smoke with a bad tube. You could also fit 1-ohm cathode resistors if you want to measure current easily for tube matching.

    You also need a dummy load (or an attenuator with a load setting).

    That way you'll be able to test tubes in the way that they need to be for a guitar amp. Tube testers don't really. They're not useless at all, but they don't give all the information you need to test guitar amp tubes, and you're going to have to run them in an amp as well really. The worst problem is that most tube testers don't subject the tubes to anything like the over-design-spec voltages and power that many guitar amps do, and you can easily have a tube which will pass on the tester but fail in an amp - sometimes causing amp damage as well.

    And to really know whether a tube is good for a guitar amp, you need to listen to it - for microphonics especially, but if you're using a half-decent old tube amp as your tester, you can listen to the sound too.
     
  3. Plexed

    Plexed Member

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    Thanks John!

    I was going to pick up a tester for my Univalve, and I think I came to the same conclusion you basically outlined. The best tube tester is an amp. I just put the tube in my Univalve and then I use my ears! I think I'll end up saving some money and get a clearer idea of what a tube actually sounds like.

    Best,


    Plexed
     
  4. Plexed

    Plexed Member

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    The Uni is actually a great little amp with a ton a options. I don't think the Uni has any type of bias points, but it is not necessary, as the amp is self biasing. I have run EL34, 5881, KT88, and an EL84 w/yellowjacket adapter. I also have tried some beautiful NOS pre-amp tubes. One issue with the amp is actually just leaving it alone and not tweaking the tone all the time. The Uni is a ton of fun and has great tone. It is like have a music lab in your studio. I would say it does a lot of great sounds from clean to classic/hard rock. The only area where the Uni hits "some" limitations is some of the Nu-Metal type sounds, and I suppose with the right pedal you could get close, but that's not really what the amp's about. Check one out, they sound great. Take a look over at www.univalve.net there is a ton of info and satisfied customers!

    Best,

    Plexed
     
  5. BPlexico

    BPlexico Gold Supporting Member

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    No Bias test points on a Univalve - fun amp though...

    -- Barr
     
  6. BPlexico

    BPlexico Gold Supporting Member

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    Geez, if you weren't in Scotland, I would happily send you my Univalve (with appropriate fee), so you could both try one and fit it with a bias test point....actually I would probably still do it if you were willing to pay return freight...;)

    -- Barr
     

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