I just received the Yaqin MC13. It has one AX7 tube missing out of the 4 preamp tubes. I have ordered that. I did run it without it thinking that it will at least run one channel. Connected a TT with built in preamp to Mc13. But ran into issues. First was that there was huge music volume out of one speaker (b&w bookshelf pair). Unbearable kind. And volume was still at ‘zero’. So I immediately switched it off. Then without removing the TT input from Aux1 in MC13, I switched the Input at front of MC to AuX2. And Aux2 doesn’t actually have any input connected. Note that the TT is still connected to AUX1. Started the TT and then I hear music from the speaker at very low volume. Still the volume knob makes no difference to volume. Note that increasing volume when input 1 Aux1 was selected does increase the volume a bit from what was too loud for the speaker to handle and it almost destroys my speakers. Any idea what is happening to my amplifier and why is it behaving this way? Is the missing 12AX7 causing this problem? I do want to upgrade this as soon as we get this working. Thanks for response in advance. I do want to like this amp!!