Tube Pre-Amp Question

You are probably hearing tube 'rush' from less than the quietest tubes, or you are hearing the pre-amps' intrinsic noise floor. Do you only hear this with you ear within inches of the tweeter? If so I wouldn't be concerned, its not unusual.

Here is away to check it out....Play some music loud. Don't touch the volume control but turn off the source. How loud is the 'hiss'? If you can hardly hear it don't be concerned its very normal. If it is loud it could effect the 'black' background prized by many.

If it is loud at normal playback level I'd consider getting new low noise tubes, not necessarily a different brand unless you cannot get good low noise tubes of that brand.

PC's and IC shouldn't improve or mask this noise in any meaningful way.

If the hum changes with an increase in volume it is likely that it occurs in a source/pre-amp connection, or a component part or tube in the unit that preceeds the line amplifying section of the pre-amp. I'm not familar with the VTL but if it has one a rectifier tube could be a problem as could a tube in the phono stage (if it has one).

I would suggest that you disconnect all of your sources and see if the hum goes away. If it does then add them back one at a time checking the results.

That will get you started.