I purchased this item used, in excellent condition, with minimal prior use. Initially, in Tube mode, there was no sound from the left channel (or the sound was extremely quiet?). It seemed like there was an issue with the vacuum tube. In AB mode, the sound was normal. Upon re-testing the unit for this listing, the menu switching and volume adjustments stopped working. The dial was unresponsive. After some time, the dial started responding again. I don't know under what conditions the problem occurs. Please consider this item as junk. Since it's used, there is no warranty. I haven't used any of the included accessories except for the case.