2. amps-preamps
  3. 1096239202

Tube brightness and bias

I have a pair of VTL Deluxe Mono 120 and I notice that one of them have its tubes lit up quite a bit brighter than the other although all the tubes have the same brand name. It also comes on a lot faster, about 4 or 5 sec, than the other. If I turn on the preamp first, then turn on both amps at the same time, then music from the amp with bright tubes comes on about 4 or 5 sec before the other.

I don't have much experience with tubes but I wonder if this has anything to do with the tubes being either over or under biased. If I reduce the bias, would the brightness then reduced?
andy2

Showing 1 response by elevick

elevick
2,638 posts
 
First of all, if the tubes are glowing hotter (probably blue), shut it off. This is probably a bias problem. You are killing the tubes if burning too hot.

Even if it is simply a bias problem, you should have a tech do the biasing. His hourly rate is much less than 2 matched quads of tubes.

The problem could be simple as bias or much more. I would get it checked out.
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