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Discussion Starter #1
One month ago I purchased a McIntosh MC-275 Mk IV to replace my MC-250 for two-channel and home theater listening. Terry DeWick restored my MC-250 to specs last year.

Back in 1970 the MC-275, 75 watts/channel, sold for $444 and the MC-250, 50 watts/channel, was $379 (the MC-2505 sold for $449, the blue meter version of the MC-250). Based on the similar prices one would assume they would sound about the same.

Listening test:
I used Chesky’s Ultimate Demonstration Disc to test the amps. The Chesky CD is well recorded and easily available, and I have spent many hours listening to it. I have listened to many other CD's in the past month. The system consisted of Klipschorn’s, Cambridge Audio Azur 640C, Denon AVR-3200, and Monster cable.

High resolution: Spanish Harlem. Rebecca Pigeon’s voice was very distinct and filled the room, the MC-275 seem to put a ‘halo’ around her voice. Heard more of a sharper distinction in the vocals with the MC-250. Edge MC-250.

Depth: If I Could Sing the Blues. Virtually identical. Placement of the trumpet is identical, about 15 feet behind and to the right of the microphone. Tie.

Midrange purity: Grandma’s Hands. Near the end of the song you can hear tapping of feet, seemed more distinct with the MC-275. With the MC-250 sounded like they were wearing tennis shoes, with the MC-275 they might have been wearing dress shoes. Edge MC-275.

Holographic Imaging: Festival Te Deum. You certainly can tell this piece was recorded in a large cathedral. No edge to either amp. Tie.

Bass Resonance. Maybe more detail in the MC-275, especially as the fingers moved down the strings. Slight edge MC-275.


Appearance: Edge MC-275. Who can resist the glow of tubes?

Measurements:
Measured the room response curve of both amplifiers using full range test tone from Room EQ Wizard. The MC-275 seems a little flatter in the higher ranges and does a better job at 12-17 KHz. Lower end the curves track real close. Edge MC-275.


Overall: Slight edge to the MC-275.

Conclusions: The newer MC-275 Mk IV beat the MC-250 by a small margin in my very subjective tests. Is the difference in price between the MC-275 at $3,900 and MC-250 at $450 (after a going over by Terry DeWick) worth it? The MC-250 is one **** of a value. Very warm, tube like sound at 1/8th the price!
 

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Back in 1970 the MC-275, 75 watts/channel, sold for $444
I remember reading the classifieds in the back of Audio magazine(now defunct)in the late 80's and seeing original MC275's selling for $5000 if they were in mint condition.I had an MC240 and it had that magical Mac tube sound.Unfortunately I sold it many years ago.:crying::duh:
 

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Discussion Starter #4
The graph in the above post showed how the amplifiers worked in my listening room. The only way I could remove the room from the equation is to use an anechoic chamber, which I don't have. As I have done before, I piled 2" and 4" bass traps (OC-703) around the left speaker to remove as much of the room effect as I could. Here the MC-275 Mk IV really shines, much smoother and flatter curve.


A good question to ask is how effective my pseudo-anechoic chamber is? I made a measurement with the left speaker (in the chamber) off and only right speaker playing. As expected the low frequencies were not blocked, but it did a terrific job with the high frequency.

 

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Discussion Starter #5
This graph compares the MC-275 Mk IV with and without room effects.
 

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Discussion Starter #6
This graph compares the MC-250 with and without room effects.
 

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