First off, I don't own this amp but am considering buying it. Channel one, the three knob channel has very little volume and is crackly. Channel two sounds fantastic. The shop says it's a $75 fix but didn't actually know what's wrong, great right? Any idea what it sounds like? Is that the EL84 channel? Thinkyof taking some tubes with me and swapping them out to try. It's not the newest model with K master but I'm not sure the year.