First time tube preamp owner - should all tubes be lit?

[Bollenator]

Hi all,
Just a question from a Tube Nube.

In my newly acquired ART Tube Channel preamp, I only see one of the two 12AX7 tubes glowing through rear air vents on the unit - should both be glowing?

I've played through it and it seems to work fine, but I'd like to be sure (though I suppose "certainty" would be having the tubes tested... maybe that's the next step).

Thanks!

[MuzikMan]

I don't know but I would try switching them and see if the glowing stays with the tube or the socket.

[billfitzmaurice]

If it ain't broke don't fix it. Not all tubes glow in the same fashion. You'd probably see both glow in a dark room with the lights out.

[BassmanPaul]

+1 to Bill's post. Some tube heaters are not as bright as others and IIRC the ART products run their heaters on DC which can make them even harder to see.

[Bollenator]

Sounds good guys, thanks for the advice. I'd been wanting to crack open the case just to see what's in there, and it turns out that the dark tube is a 5751, so (after doing a little research) I would assume the lower gain of the 5751 means it would be less likely to glow.

Even if that's completely off the mark, I'm now confident that there's nothing to worry about. Thanks!

[BassmanPaul]

No the heater has nothing to do with the gain. It's the tube structure that does that.

[Bollenator]

Like I said, "off the mark."

[BassmanPaul]

Originally Posted by Bollenator

Like I said, "off the mark."

Leave Mark out of this - what did he ever do to you???