McIntosh C 220 Pre amp tubes...

12x7s should last you 5000 hours, approximately.
It pays to get them tested.
You could try some tube rolling though...

Any tubes that came stock with it are junk, sorry to be so blunt.And McIntosh runs there tubes hot! You might get 2-3k hours if your lucky with stock tubes. Call Andy @vintagetubeservices.com 616-454-3467, And be patient, Andy is old school and he knows his shit when it comes to NOS (new OLD stock) or OLD original tubes that will sound better. Try some REAL mullard 12ax7's or 12at7's or Amperex ECC83's or ECC81's.You will be astonished at what a difference a good pair of these little guys can do for your sound. Tube roll its fun!

Thanks Guys! I would like to try some different ones. My pre amp is rather flat sounding...and I'm wondering if different tubes would add more body to the sound. I just hope they're easy to get at and replace. Thanks for all the good advice/insight thus far!!

Any suggestions on tube brands you like? Are Mullard nice ones to go with? Read they're robust and pretty 3D sounding. Not sure what a nice brand to go to would be. Perhaps I should call the guy mentioned above. Thanks.

I don't think old tubes necessarily sound better these days as a lot of new stuff from Russia and China have stepped up and are less expensive. I do use a pair of UK made Mullard 12AT7s (CV 4024) which provide an entertaining flare up when initially turned on (highly recommended, and not expensive). Thetubestore.com has their "preferred" Chinese 12AX7s which sound great, but an even better non-vintage tube might be the Chinese Psvane 12AX7-T (treasure?) series II which has gold pins, etc., and sounds amazingly good. Get those from Grant Fidelity in Canada as I had issue buying direct from China (!).

Check Grant Fidelity - Psvane Treasure high-grade tubes. I use them in my C2300. I have tried Mullards, Teles (ribbed), Gold Lion, Mazda, Sovtek LPS, etc. The Psvanes have won.

Thanks for those inputs above guys...very helpful! Enjoy hearing what you use.