problems with groove tubes

[kamilwysocki]

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.

 

[chucko58]

If they make sound, who cares if you can see them glowing?

 

[Nighttrain1127]

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.

 

[beans-on-toast]

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.

 

[B-string]

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.

 

[JFOC]

Some tubes will "flash" on startup (for example mullards) while others won't illuminate at all (sovtek lps)

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[Mr. Foxen]

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.

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.