I've put my eyes on an used Kustom DE 300 HD head. The asking price is right. The guy states in the ad that sometimes volume cuts out for a second or two, and says the fault is in the old, "tired" preamp tube. Since a new tube isn't much money, and what i'm reading of this head so far is convincing me, I'd quite inclined to splurge. However I think it's best to check with you folks! Could it really be just the tube or it could be a symptom of something far more troublesome? I contacted the guy for more info and I'm to call him this evening, is there anything specific you think I should ask about?