Eden Navigator hissssssss.....

You might want to pull the tube out and reseat it. This would clean any corrosion that may have built up. If that helps you might want to get some contact cleaner like Craig's De-oxit and spray a small amount on the tube pins then reseat it (amp power off of course).

BTW did you ever get the tube issue ironed out on your Aggie DB680?

 

My Nav/QSC setup is dead quiet. I would think the tube would be the first thing to check. Let us know what it turns out to be.

 

One 12ax7

 

And mine had the original Chinese no-name tube in it. So I though that it would sound better with some really nice NOS tube like a Mullard or a Telefunken. Was I ever wrong...it got all mushy sounding. I think that David N. tuned that preamp and the rest of the line to sound the best with a common tube. So nobody would be searching endlessly for some unobtainium tube. Very forward thinking.