#1
Hey guys,


SO a couple years back I purchased a Crate BV120 head on ebay. I had issues with really little headroom, and eventually decided it was due to the undersized cab I'd been using (a 4x10 Crate cab that was physically too small to set the head on), and went ahead and got the Blue Voodoo cab online.

I'm still having issues with the clean channel driving as early as around a 3 or 4. Looking at the power tubes (I've replaced them once, but did not have it biased, as I'd read that the Voodoo is "self-biasing"), I've noticed that regardless of swapping the positions of the tubes, the one to the far right burns the hottest, with a blue glow, while the far left two only get warm, and the second from the right doesn't heat up at all. Is this because the Voodoo does actually need to be biased? Any thoughts on what could be wrong with this? I'm running Sovtek 6L6WXT+ tubes in it now.

Thanks in advance!
Last edited by tregnoto at Jun 11, 2013,
#2
It is not self biasing, there is a trim pot you adjust the bias with.

Did you replace all of the 12ax7 tubes in the amp?
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#3
Changing your power tubes isn't really going to help your headroom.

Yes, you should have it biased by a competent tech, but you need to look to the preamp to start working on your headroom concerns.
“Ignorance more frequently begets confidence than does knowledge.”
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#4
I have not had the preamp tubes changed since I purchased the amp. I noticed, in switching the original tubes in for the Sovtek tubes that I purchased, that the old tubes exacerbate the problem pretty drastically. Does this mean that power tubes as well as preamp tubes have to do with the headroom? Also, in regards to the tubes heating very differently, is this something that generally happens? Or could it be caused by the old preamp tubes?

The preamp tubes seem to glow pretty evenly when I play with the covers off.

Thanks for all the info, folks!
#5
The power tubes should be biased. The trim pot is internal. Take it to a tech for that. I would be worried about the bias being very cold.

Tha being said it sounds like you need to replace your preamp tubes. Do this first. Get 4 JJ's.
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