I've had my VT 50 for about 3 years. Get's light use ... 7 gigs and probably 30 practices in that time.
About 3 weeks ago plugged in and got almost no volume out of main speaker and very distorted amp sounds. Each amp and preset was different but scratchy, distorted and very faint volume.
Tried the headset and everything sounded great. Tried several factory resets -- no luck -- same problem.
So on a hunch replaced the 12AX7 tube and ... viola ... volume back to normal.
Unfortunately 4 practices later and bam it is back to very low volume fuzz. Suspect the tube is shot again. I could and will need to replace it but, need to figure out what is causing it to fail. My bro who has had tube amps for many years is surprised and says that these types of pre-amp tubes rarely fail.