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Old 08-31-2022, 04:07 AM
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Default McIntosh KT88 and 12AT7 tube impressions/experience

We've owned a pair of McIntosh MC2301 mono block power amps now for 4 1/2 years now. I bought a set of new Genalex Gold Lion tubes (16 KT88s and 4 12AT7s) back then, but waited until now to roll the Gold Lions in and replace the stock McIntosh branded tubes (my understanding is they are made by JJ for McIntosh). There was no special reason to roll now, except that our son is in town, and was willing to help wrestle these heavy amps and do the rolling with me. After the Gold Lions burn in a bit, I may compare, but this post is about the stock tubes and hopefully may help someone thinking about buying tubed gear.

The amps have been in service for about 44 of the 54 months we've owned them (put in storage for 10 months while we lived in an apartment while building our current home). I'd guess that we've averaged between 2.5-3 hours playing per day, which may seem a bit high, but they are used in the home theater setup as well as stereo from the C1100 preamp. That puts our usage on the tubes at ~3,700 hours, likely a bit higher.

I have an Orange VT1000 tube tester, which does a number of tests, but only shows an output of Good/Worn/Fail vs. detailed readouts of the individual tests. All the tubes showed Good and a numeric ranking of 7-11, with over half of them rating an 8. The upshot of all this is that the stock McIntosh power tubes were still going strong, and I plan to keep them since they test well and sound fine, and can function as backups.

These amps were our first major foray into tubes, and I had a lot of questions about going over from solid state amps, not least of which were regarding tube life and the possibility of degradation in sound over time. The bottom line is that my experience with the McIntosh stock tubes is that they have performed well for something approaching 4,000 hours and still have plenty of life in them. This isn't exactly a revelation or unexpected, but may help someone considering a tube amp for the first time get an idea of what ownership entails.
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Sources: Vinyl: Clearaudio Innovation Wood turntable with 9" Universal tonearm, Da Vinci V2 cartridge, Stillpoints SS & Stillpoints clamp, McIntosh MVP 901, Apple Mac mini via Benchmark DAC 1, Aurender N100C via Schiit Yggdrasil
Control: McIntosh C1100, Mcintosh MX151
Power: Mcintosh MC2301s (front), McIntosh MC501 (center), Mcintosh MC402 (rear)
Speakers: Sonus Faber Amati Futura (front and back), SF Vox center
Power/connections: PS Audio Power Port receptacles, RGPC 400 pro (2) WireWorld interconnects and speaker cable
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Old 08-31-2022, 08:10 AM
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Thanks for this post. It's long been suspected, but never comfirmed, that the stock Mc tubes are OEM branded by JJ Electronics. I have the MC1502 that is now only 4 months old, but I am logging hours on it mostly every day.

There's always been a bit of concern over tube life, especially for power tubes. The only other power tube experience I had before this amp was an integrated that ran 4 Tung Sol 6550's. It seems one tube went bad (never found out which one) as the amp kept shutting down after just a few minutes of use. Once I replaced all 4, the amp never had a problem again. My memory of that episode was that I didn't have a lot of hours on the amp, but at only 65 watts, I did run it pretty hard. 10 to 15 years ago tube prices were a lot less than today, so with 8 KT88's in the mix, longevity is a worry.

FWIW, my brother has the MC275 MkVI. Like you, he runs his amp several hours a day pretty much every day and has been doing that for the last 3 years. So far he reports no problems at all. Hopefully his and your good experiences will be echoed by me 4 or 5 years from now. Time will tell.

I realize you didn't start this thread for the purposes of comparing the stock Mc tubes to the Gold Lion tubes, but could you give us a short word or two on how you feel about the sound of the new tubes over that of the old. It would be much appreciated.
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Old 09-01-2022, 03:01 AM
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So one more bit of data on the tubes, this time the 12AT7s (2 in each amp). One did test as just inside "Worn" territory vs. "Good", which was a bit unexpected given that it's the power tubes that are supposed to have a shorter life. It may have also contributed to a feeling the sound was maybe a bit flat, but not something I could put my finger on since any degradation would have been so gradual I would not be conscious of it.

Freddie, great question about a comparison and one I didn't want to delve into on the initial post because I had maybe 2 hours on the new tubes. Now I have 5! So, the caveat that they really don't have enough time to be broken in aside, there is a bit more detail and punch with the Gold Lions. In fairness to the stock tubes, we're comparing tubes with considerable use vs. new ones, with one testing "Worn" vs. "Good". My 26-year-old son, who has musical talent and a better ear than me, said he feels it sounds better. He showed more interest in listening this evening, which is telling. You've got to be enjoying that MC1502!

I know some folks have replaced their stock tubes with Gold Lions (or other tubes) right away, something I decided not to do since this was my first foray with tubes in the main system (replacing MC501s), and I wanted to get used to the "house sound" as well as "utilize the assets" of the stock tubes. It also seems wise to get used to a set of tubes before making a comparison, especially with 16 KT88s which isn't cheap and almost twice as expensive as it was in 2018, although you don't need four years to do that! I like what I'm hearing with the Gold Lions, but don't regret waiting since part of having tubed equipment is that it can be more of a journey and allow for some experimentation, depending on how much you want to roll tubes. That said, I can see why someone with the right experience would swap out stock tubes if he thought he had something better, just set it and forget it and focus solely on the music.
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Sources: Vinyl: Clearaudio Innovation Wood turntable with 9" Universal tonearm, Da Vinci V2 cartridge, Stillpoints SS & Stillpoints clamp, McIntosh MVP 901, Apple Mac mini via Benchmark DAC 1, Aurender N100C via Schiit Yggdrasil
Control: McIntosh C1100, Mcintosh MX151
Power: Mcintosh MC2301s (front), McIntosh MC501 (center), Mcintosh MC402 (rear)
Speakers: Sonus Faber Amati Futura (front and back), SF Vox center
Power/connections: PS Audio Power Port receptacles, RGPC 400 pro (2) WireWorld interconnects and speaker cable
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Old 09-01-2022, 08:36 AM
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Nice report. Thanks.
I've always enjoyed tube-rolling in my amps (though 2 power tubes per channel has always been my max). So much so I'm second-guessing my choice to go back to solid-state.
If there was not so much expense involved I would suggest trying a set of 6550s if the MC2301 allows for same (as does the MC275/MC75/etc.). In my MC275/MC75 amps I found the 6550s to have a bit better mid-range and not quite the bass.
My experience with GL tubes was the same as your report. A small, but noticeable improvement over stock. Plus, considering the cost of McIntosh branded tubes I always preferred to run GL or Tung-Sol and have the stock tubes on the shelf.
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