Mc2301 turning off

[Masterlu]

Originally Posted by audioguru

Interestingly enough, I had the exact same issue as described by Ischoonaert with one of my brand new 2301's. In a way, I was fortunate in the timing, as at that point they were still basically brand new (less than 2 months old) and that my local dealer and Mcintosh took great care of me, and essentially swapped out the faulty amp for a brand new unit. Mcintosh suspected that it was a faulty tube somewhere, but apparently after having the local tech do a full run through of the amp, and test it extensively at load, they were not able to replicate the problem. Since I have had the brand new replacement unit, it has performed flawlessly, so I am hoping it was just "beginners luck" with a faulty tube somewhere in the original unit.

Nice System, why not post some photos in the Members System forum.

[audioguru]

Thanks Ivan! I am not quite yet at end of job in building my "Dream" 2 channel Sound Room, but will post some pics of the work in progress so far.

[edkoz]

Originally Posted by audioguru

Thanks Ivan! I am not quite yet at end of job in building my "Dream" 2 channel Sound Room, but will post some pics of the work in progress so far.

looks like you have a great system. Looking forward to seeing some photos as well.
Ed

[lschoonaert]

SO one week without any sentry kicking in (after replacing the tube that measured below the other tubes, 7mA/V instead of 9mA/V) - I thought that McIntosh amplifiers were not
sensitive to biasing and matching tubes, or maybe I'm just mixing things up.

Below is a good article about matching tubes :

https://www.apexmatching.com/why-sho...match-my-tubes

[vintage_tube]

It could have been seeing an intermittent short -- who knows. Throw it away & move on.

Tubes do act strange at times. Glad to learn of your MC2301 behaving now.

Best Sir,

Bob

[vintage_tube]

How old are you amps? Did you get them back in 2009 by chance?

Best Sir,

Bob

[lschoonaert]

@Bob: I have no clue - I bought them from someone in 2015, he had owned them for a few years already. The tubes I put on this year in may were brand new - but it seems one was acting up... come to think of it - that new set of 16 power tubes, when it arrived had 1 broken tube that was swapped later on. Maybe those were 2 matched sets of 8 and this new tube didn't match... oh well, we'll never know, just that it was a tube

[vintage_tube]

The reason I ask Luk is McIntosh issued bulletin 'MC2301.SB01', issued June 8, 2011!!! The PDF discusses the two original types of Svetlana KT88s used in the older MC2301s.

McIntosh specifically warns about the old Svetlana KT88s (McIntosh Part No. 16507000) with the 'Small Round Holes'. McIntosh states 'Do Not Use This Tube in the MC2301 Power Amplifier'!

The other Svetlana KT88s, with the 'Rectangular Holes' (McIntosh Part No. 16506900') are acceptable. They also discuss another McIntosh-branded KT88, with 'Large Round Holes' (McIntosh Part No. 16507300 & 16507400) which are OK to use.

Ron Evans, now retired and designer of the MC2301 told me power tube matching to tight tolerances is not critical in the MC2301 (nor any McIntosh tube amp). He did say, and makes sense, the hardest working tubes in the MC2301's are the 12AT7's.

Best Sir,

Bob

P.S. Thanks to Ken (kb7215) for some of this info. I lost it when my HD crashed.

[Ventoux]

Question about Tube pair matching (since this is related)

I also have a pair of MC2301's (never been setup - as remodeling my home & listening room is in progress). I recently purchased a whole new set of Genalex - Gold Lion tubes (16 - KT88's and 4 - 12AT7's). I asked for the matching pair option. When they arrived they all came in sets of 4 (rubber banded together) They also have numbered stickers with 4 tubes sharing the same number. So, my question is: I'm assuming that I can pair the same tubes with the same number. And, in what order would I install them in the amps? Left side - match right side with same number. Example: 2 #34 on right and 2 #34 on left, and so on.

Thanks Bob - ahead of time

[vintage_tube]

Do it in quads -- The tubes are grouped into two quads, one in the front of the amp, one in the rear. The front four tubes (V5+, V4+, V1- V2-) are one quad, the rear four tubes (V1+, V2+, V5-, V4-) a second quad.

Take a look at the amp when you have a chance and it should be much clearer when you notice the + and - signs.

Best Sir,

Bob