Hi! A few months back, I picked up a Blackstar Artist 15 for a great price. I really enjoy channel 2 of the amp, but I was thinking about trying out some different tubes to see if I can get more/earlier saturation from the amp. I was wondering if anyone knows if it is possible to use other tubes besides 6l6's in the power amp. For example, I have heard that 5881's can be swapped with no issues. I was wondering if it is possible to use those or 6v6, el34 (not very likely) or other tubes as well? I am thinking about trying out some higher rated 12ax7 tubes in the preamp as well. The amp is cathode bias and I assume is running each tube in class A or it may just be the transformer that allows it to be 15 watts and use 6l6 tubes. Any advice or insight is appreciated!