I had a mc10 that was modded by previous owner. Nice amp for the money, no matter what tubes used it will never sound overly tubey. I used Mullard xf2's that I already had laying around but very pricey,I also had good luck with Winged C's. I tried the Vokshod 6n1p for Preamp tubes but it's hard to find a set of quiet ones but they are cheap and can sound good, I had a lot of 6922's or 6dj8 so I used Amprex bugle boys. I know some people say it's not same as 6n1p but I used the amp at work so it stayed on all day 4 or 5 days a week with no trouble. For me the warmer or neutral the el34 tube the better as the amp can tend to sound like a solid state amp. Then use a preamp tube that has good bass and tends to pull information from the music.