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McIntosh MI254 Power Amplifier Teardown

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Greetings, fellow ASR readers.

Long time lurker, first time poster here.

This is a quick teardown of a McIntosh MI254 4-channel power amplifier. This amp is used as a supplement to the Marantz SR6014 AVR for home theater duty. It is powering two front channels and two surround channels.

I have been a McIntosh fan ever since I saw the C712 + MC7150 set up at my uncle's place back when I was a kid. It was purchased new since the mid-90's and has been a flawless performer for over two decades. However, even though the amp is slimmer than other McIntosh models, the MC7150 itself weighs in at a hefty 26 kg (58 lbs). I assume that the majority of the weight comes from the autoformers.

C712 MC7150.jpg


Fast forward to 2019, I bought the MI254 new from a local authorized distributor. AFAIK, this is among the very first Class D amp McIntosh has ever produced, a departure from their traditional Class AB and tube designs. Aside from the MI254, McIntosh also have a MI128, an 8-channel amplifier specifically for whole home audio distribution, and most recently, a MI347 7-channel home theater amp, both of which are also Class D. Only the MI254 comes with the blue meters though.

The amp is slightly thinner than the MC7150 but weighs in at around 10 kg (23 lbs) which makes it very convenient to move around and set up. There's also an option for a professional rack mount as well.

MI254.jpg


The backside has a multitude of connections, including unbalanced RCAs and balanced XLRs, or you can switch over to Bus 1 or Bus 2 and use the amp for bi-amping or different pair of speakers. By using Bus 1 and/or Bus 2, it is possible to daisy-chain to other amplifiers for other room / zones.

Serial number blocked, for obvious reasons.

Rear.jpg


Top cover on.

Top Cover on.jpg


Removing six screws (2 in the front, 2 in the center, and 2 at the back) and top cover comes off.

Open.jpg


The amplification duty is handled by four Hypex NC500 OEM modules. The fact that it is powered by Hypex, along with great reviews, combined with the blue power meters made it an instant buy for me.

The NC500 module is fitted with Samwha capacitors, similar to many other NC500 implementations. There are separate heatsinks for each module.

NC500.jpg


The amp itself appears to be using a custom switching power supply as opposed to Hypex's own. It is multi-voltage though.

SMPS.jpg


There appears to be a mix bag of Japanese, Korean and Chinese capacitors. I have very limited knowledge on electrical designs so I can't really comment on its duty.

Jianghai CD297 capacitors, rated at 105C.

Jianghai.jpg


Here's are Nichicons. I've heard rave reviews from PC power supplies using these caps so I guess they are top notch.

Nichicon.jpg


And here it is, with blue lights on in the theater room.

Glow in the Dark.jpg


I do apologize for questionable photo quality though. There appear to be a size cap so some photos were resized.
 

Billy Budapest

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Is this the McIntosh amp that supposedly has SOTA measurements?
 
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Billy Budapest

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Any reactions on the sound ?
This is going to be a tough one to describe. I would recommend an in-store demo if you could.
Before I bought it back then, the local dealer had the MI254 matched with the Sonus Faber Olympica Nova. It sounded epic, but those speakers were way beyond my budget range.
 

Vacceo

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It would be amazing if you were kind enough to allow Amir to put the amplifier on the test bench. It is an Ncore based product, so it should be pretty good, but other companies (NAD with Purifi) have managed to provide worse results than baseline amps, so...

From this amp, we could also get an idea about the 7 channel MI347, which I think is basically the same thing in its higher power 3 main channels.
 

MakeMineVinyl

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Umm....... NC500 modules. Where have I seen those before? Is that a PIC16F690 on the modules with an ICSP port next to it? Nah, must be seeing things. :oops:
 

Vacceo

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Another question in regards to heat: will it need fans when rack-mounted with other components?
 

MakeMineVinyl

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question in regards to heat: will it need fans when rack-mounted with other components?
Class D usually doesn't generate enough heat to need a fan.
 

sarumbear

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Greetings, fellow ASR readers.

Long time lurker, first time poster here.

This is a quick teardown of a McIntosh MI254 4-channel power amplifier. This amp is used as a supplement to the Marantz SR6014 AVR for home theater duty. It is powering two front channels and two surround channels.

I have been a McIntosh fan ever since I saw the C712 + MC7150 set up at my uncle's place back when I was a kid. It was purchased new since the mid-90's and has been a flawless performer for over two decades. However, even though the amp is slimmer than other McIntosh models, the MC7150 itself weighs in at a hefty 26 kg (58 lbs). I assume that the majority of the weight comes from the autoformers.

View attachment 120612

Fast forward to 2019, I bought the MI254 new from a local authorized distributor. AFAIK, this is among the very first Class D amp McIntosh has ever produced, a departure from their traditional Class AB and tube designs. Aside from the MI254, McIntosh also have a MI128, an 8-channel amplifier specifically for whole home audio distribution, and most recently, a MI347 7-channel home theater amp, both of which are also Class D. Only the MI254 comes with the blue meters though.

The amp is slightly thinner than the MC7150 but weighs in at around 10 kg (23 lbs) which makes it very convenient to move around and set up. There's also an option for a professional rack mount as well.

View attachment 120613

The backside has a multitude of connections, including unbalanced RCAs and balanced XLRs, or you can switch over to Bus 1 or Bus 2 and use the amp for bi-amping or different pair of speakers. By using Bus 1 and/or Bus 2, it is possible to daisy-chain to other amplifiers for other room / zones.

Serial number blocked, for obvious reasons.

View attachment 120614

Top cover on.

View attachment 120615

Removing six screws (2 in the front, 2 in the center, and 2 at the back) and top cover comes off.

View attachment 120616

The amplification duty is handled by four Hypex NC500 OEM modules. The fact that it is powered by Hypex, along with great reviews, combined with the blue power meters made it an instant buy for me.

The NC500 module is fitted with Samwha capacitors, similar to many other NC500 implementations. There are separate heatsinks for each module.

View attachment 120617

The amp itself appears to be using a custom switching power supply as opposed to Hypex's own. It is multi-voltage though.

View attachment 120618

There appears to be a mix bag of Japanese, Korean and Chinese capacitors. I have very limited knowledge on electrical designs so I can't really comment on its duty.

Jianghai CD297 capacitors, rated at 105C.

View attachment 120619

Here's are Nichicons. I've heard rave reviews from PC power supplies using these caps so I guess they are top notch.

View attachment 120620

And here it is, with blue lights on in the theater room.

View attachment 120621

I do apologize for questionable photo quality though. There appear to be a size cap so some photos were resized.
You can say many things against the brand but production quality is not one of them. Their equipment are always immaculately manufactured.
 

restorer-john

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Umm....... NC500 modules. Where have I seen those before? Is that a PIC16F690 on the modules with an ICSP port next to it? Nah, must be seeing things.

You know what's in an NC-400OEM ;)

1647814541131.png
 

Vacceo

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Class D usually doesn't generate enough heat to need a fan.
That is the point: in general. Beyond the Hypex modules there is a power source and other electronics, and those could be not as efficient as the NC500. Hence the question if they can be stacked on top of each other on a rack (something that McIntosh does not recommend).
 

CinDyment

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Familiar with a wide variety of off-shore capacitors. Some good, some bad. What worries me is I have never seen printing that poor on a real Nichicon capacitor:
1647818123378.png
 

MakeMineVinyl

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That is the point: in general. Beyond the Hypex modules there is a power source and other electronics, and those could be not as efficient as the NC500. Hence the question if they can be stacked on top of each other on a rack (something that McIntosh does not recommend).
Even linear power supplies don't get all that hot. The real heat dissipation, at least in a class A/B or class A amplifier is in the output stage transistors. Switching power supplies are very efficient and don't generate all that much heat, at least not to the point which would likely need a fan.

Beyond all that, if you are finding that you are stacking your components so densely that heat is a concern, you're doing something terribly wrong. You need to physically space out the components and arrange them so heat doesn't build up.
 

restorer-john

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Familiar with a wide variety of off-shore capacitors. Some good, some bad. What worries me is I have never seen printing that poor on a real Nichicon capacitor: View attachment 194083

If you look hard at the picture, that capacitor likely has a dent in the can and that is making the sleeve print look as poor as it does. (the same effect is seen over the base-crimp on the same cap) Combined with low lighting and low resolution, the cap looks like a dodgy fake. I don't think it is.
 

Chrispy

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Even linear power supplies don't get all that hot. The real heat dissipation, at least in a class A/B or class A amplifier is in the output stage transistors. Switching power supplies are very efficient and don't generate all that much heat, at least not to the point which would likely need a fan.

Beyond all that, if you are finding that you are stacking your components so densely that heat is a concern, you're doing something terribly wrong. You need to physically space out the components and arrange them so heat doesn't build up.
So your company doesn't use fans particularly in your designs? Anything special in heat sinking for the output stage? What would you say would be any advantage/disadvantage to McIntosh's autoformers vs your own executions?
 

MakeMineVinyl

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Some of our amplifiers, and the professional amplifiers in particular, use fans which are thermally controlled. Most of our amps don't use fans. We are known for large heatsinks and beefy construction.

Autotransformers vs conventional is really apples to oranges. No particular shortfalls in either approach.
 

Doodski

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Familiar with a wide variety of off-shore capacitors. Some good, some bad. What worries me is I have never seen printing that poor on a real Nichicon capacitor: View attachment 194083
The outer sheath that you see is shrink wrap and it sometimes distorts when being shrunk/applied. No cause for worry. If it is really stretched and splitting then the capacitor is bursting open and needs replacing but in this case it's just distorted dimensions from the shrinking process.
Nichicon 2.jpg
 
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