I have a C2300 and highly recommend Amprex Medical Grade 12 ax7s, they are extremely pricey but ultra quiet, rugged and will last for years. I’ve had mine in for 4 years and my preamp is on literally 6-7 hours a day (as a passthru in my home theater system) and it sounds wonderful. I only use the medical tubes in the MC Phono stage and the Aux stage because I don’t have a MM TT. This is a great preamp that is smooth and sophisticated without the DAC on board, that is preferable to purists like me. I hope you continue to enjoy your C2300!
Tube rolling on MacIntosh C2300
I want to try out some new tubes on my C2300 preamp. I only have one source, a DAC/Streamer and do not have a turntable. The preamp has 6 tubes of which 4 are for phono (2 MM and 2MC). Should I change the phono tubes as well or since I am not using the phono stage, it will make no difference?