Hello all. I recently purchased a used Marshall DSL 100H. I swapped out the pre and power tubes. Sino/Tube Art/Ruby El34's (supposed to be all the same rebadged tube) and a preamp "tone kit" from Doug's. Here is the weird thing that's happening. The pair on the left can be biased anywhere from 50mV on up. The pair on the right can only go as cold as 69-70mV. Adjustment screw is maxed out in the cold direction. So, I swapped sides. The pair THAT WAS on the left are now on the right and they will only go as low as 69-70mV now. So it sounds like an amp issue. BUT! I put the stock Marshall tubes back in and both sides can go as low as 50mV. So, not the amp, now? I'm not saying i want to bias it at 50mV, but I cant get the right side colder than 69mV even if i wanted to. The Marshall tubes allow me to go colder though. I've swapped these tubes multiple times with the same outcome. Does the amp just not like these Chinese tubes or what.. Any help??