McIntosh MC275 VI preamp tubes

Re-reading this. Small signal tubes last a long time. You sure your KT88s are not getting tired? I suspect they might need re-biasing, if not replacement. 

you may want to test the input tube for performance. As others have noted, they usually last quite a while. If you do not have a MC tester, some places offer testing for a reasonable price 

I bought 6sn7’s from Brent Jessee for my Cayin Integrated Amp. I always test new tubes when I receive them, they were good.

http://www.audiotubes.com/12ax7.htm

I did not like their sound.

He had me wait and listen after breaking them in (60 hrs), and if I still didn’t like them, return/exchange them. I paid shipping, bought less expensive tubes, they sound terrific, and got a full refund for the originals.

Make your best guess, buy from Brent, see if they sound good, Oh Happy Day, if not, try another.
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Do you have a tube tester?

they give you good clues, and confidence in existing and new ’matched’ tube sets. find problems, find non-problematic but weak(er) ones ..... I test all tubes annually prior to Thanksgiving, ready for the Holidays. They last a longgggggggg time.

My simple tester always agrees with my big one, I don’t bother with the big one any more. All 17 tubes of my McIntosh mx110z’s tuner/preamp tested good here. Audio Classics overhauled it, they didn’t replace any tubes, (surprising from past experience with others). That gives you more confidence in them as well as my tester.

Why not buy exact replacements? I may be counterculture in an audio forum but what’s wrong with the date you brought?

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Because anything is better than the current stock Mcintosh super cheap Chinese valves they sell at 100 times the price THEY paid.. Talk about CHEAP valves.. Under 5.00 each in bulk. 3.00 usd, is more likely.

But there are people in some countries trying to sell them for 2-4k. because of the 10.00 wooded box they come in, and the word Mcintosh burnt in the wood.. 300.00 usd worth of CHEAP valves at best.. JUNK..
The shipping cost more than the actual valves..

Regards..

@ mrklas, I concur with @oldhvymec.  When I first got the MC-275 it sounded really good...much better than the parasound A23 I had.  However, it was a little bright and the bottom end sounded thin...again, still better than the Parasound.  I did seek out Brent Jessee, and bought a mix of Tung-Sol and Mullard's...I think (it's been 4 or 5 years), and it changed the sound, a little more well rounded overall, but still wasn't entirely happy.   I ended up settling on used RCA tubes that I got from an estate sale.  The best sounding so far.

@noromance , It could be the KT-88's, but the reason I'm leaning more toward the preamp tubes is because the Golden Lion KT-88 I purchased new.  I also have a Golden Lion new 12AX7 in the inverter spot.   As I mentioned, the 12AX/AT7 were used RCA's from an estate sale.  That's why I suspect those over the power tubes.  I will say the RCA tubes are just absolutely excellent with my system. 

I was emailing back and forth with Ron Cornelius from Mcintosh in 2016 when I first got the MC-275.  He mentioned that the tubes should last on average 5000 - 10000 hours unless driven hard for long periods of time (something that can easily be accomplished by myself as a preferred metalhead, hard rock, blues, then jazz fiend in that order).  He also mentioned that the Mark VI version has the color changing LED's when a tube goes bad, but it's only for a catastrophic failure.  It does not alert you when a tube is getting weak.  

My friend and I went in on a tube tester years ago....but I ended up moving only 13 hours away...so checking the tubes is a bit of an endeavor.

Years ago I heard that the Telefunken tubes would be the best if I could find them and afford them (at the time they were running about $300 - 400/tube).  I see that they are making new black diamond Telefunken tubes...has anyone tried them before? 

If push comes to shove, I'll pick up a batch of RCA tubes.  I am just beginning to worry about how much life they have left in them.  I just wonder if the Golden Lion KT-88's have been as good as they are, then how about their 12AX7 and 12AT7's are.