The 4th of July weekend required I break out the vintage McIntosh MC275 amps not from a historical perspective but out of necessity. The Acoustic Research Reference 160M seemed flat after a proper warm-up and system test. Flat enough, that motivated several tests, followed by swapping the amps with the previous champions of my system, the MC275s. However, for this quick swap, I used 2 of the MC275s in mono-block mode or a straight swap-out with no changes to the speaker driving regarding horizontal or vertical Bi-amping.
The vintage MC275s played well, in fact, better than I remembered, so I took the time to run a few sound tests and reference sources. And yes, it was better in detail and just as strong in the realization of the music. The imaging and the resulting sound stage were also at par. Remember, the system with the vintage MC275s had 4 driving the ATC 150 speakers; 2 in mono-block mode for each of the low-frequency drivers in each speaker, a 3rd amp driving both mid range drivers and a 4th driving both speaker tweeters and super tweeters coupled with the vintage C22 preamp. What changed? What made the MC275s produce an improved performance? Perhaps the MC275s just wanted to show off after being on the shelf so long and watching the ARC Reference 160M perform 😊.
Nope, not jealousy; less is more in this case as it relates to detail and the ability to match and balance 2amps vs. 4amps. But there is another change I did not test in the past, the coupling of the outstanding Nagra HD Preamp and the vintage MC275 amps. That is a significant upgrade you can clearly hear, and the pairing of the devices is spot-on perfect; they perform very well together, delivering sound you can feel.
The performance was good, I will test this again with the ARC Reference 160M after I roll the tubes. I suspect; the ARC amps need all tubes tested and ultimately replaced, which I will do next week. After I get those replaced, I will make the comparison again and post the results. Perhaps the MC275 amps will jump back into the system…..hard to predict that given the ARC performance I remember from before.
One big takeaway; the Nagra HD Preamp is a killer with vintage MC275 amps with the correct tubes, capacitors and resistors.