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problems with groove tubes

Discussion in 'Amps and Cabs [BG]' started by kamilwysocki, Mar 25, 2013.


  1. So I went down to the local music shop and picked up some groove tubes preamp tubes(12at7c). Popped em in, warmed them up..and..well, they seem to work. The only concern I have is they are not glowing. I had to turn off the lights to even notice any glow at all. Of course i cant return them. Are they dead? Did I install them Wrong? Do groove tubes Suck in general? Any input would be much appreciated.
     
  2. chucko58

    chucko58

    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    If they make sound, who cares if you can see them glowing?
     
  3. Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    Preamp Tubes are much lower voltage then power tubes so they usually just faintly glow.. If they light up like a power tube then there is something wrong. I think with Pre tubes the only thing you see glowing is the heater in the tube.
     
  4. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Tubes will glow to different extents depending on their construction. If the heater structure is shielded, you will not see a glow, or not much of one. This doesn't mean that the tube is bad.

    As others have said, if it works don't worry about it.
     
  5. The amount of "glow" you see depends on the design the manufacturer used. If you hear sound they are working and the amount of "glow" you can see means nothing. Some tubes have a bright flare of light before they settle down to a orange glow. Different techniques of manufacture is all.
     
  6. JFOC

    JFOC

    Oct 23, 2010
    new hampShire
  7. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    If the bit with the high voltage is glowing, your amp is broken. With weird exceptions, pretty much all valve sin instrument amps run off the same heater voltage.
     

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