Tubes Recommendation for McIntosh Preamp

Great.  Thanks @bondmanp!  

Also, FWIW, on a C2500 I swapped in NOS Telefunken 12AX7.   Huge  improvement across the spectrum.    

Thanks @whitecap!   

For what it's worth, I own the McIntosh MA352 Integrated Amplifier which uses 2X 12AX7A tubes and 2X 12AT7 tubes.  I believe McIntosh sources from New Sensor but I don't have direct confirmation from the company.  I've been using the stock tubes for five years now without any issues.  The sound is great and I have no complaints.  Recently, I replaced the 12AX7A stock tubes with a matched pair of low micro-phonic 1960s Amperex Bugle Boy tubes for comparison.  I bought these tubes about a decade ago.  I stored them when I sold my tube equipment.  Having heard the stock McIntosh tubes versus the NOS Bugle Boys, the McIntosh tubes sounded better to me.  The stock tubes are more crisp (clarity & imaging), quieter (sound stage), and the bass was significantly tighter.  Additionally, the NOS tubes cost $130 a piece while current issue New Sensor (Russia) cost less.  Needless to say I put the stock 12AX7A tubes back into the equipment.  I do know that McIntosh individually tests their equipment with the stock tubes prior to delivery to ensure the best sound and compatibility.  Save yourself some money; instead of buying NOS tubes, it might be useful to consider premium New Sensor tubes as an alternative.  Cheers!

Thanks very much @wescoman for sharing your experience, Very helpful.

I actually think the current sound is not bad with the stock tubes. I was told the unit was about 1 year old, but I don’t know how many hours did the previous owner put in on the unit,

I have no experience of what a bad tube sounds like. So I thought for my own peace of mind, I would try some new tubes. But it is so good to know that you are running the stock tubes for 5 yeas without any problem. That’s wonderful!

I might just leave it for a while and see how it goes!

Thanks!