McIntosh MI254 Power Amplifier Teardown

[DVDdoug]

MacIntosh says that a reason for using them is that speakers of all impedances can get full power from an amplifier.

For those of us who are more economically-minded...

It's more economical to build an amp that can put-out the necessary power at 8-Ohms even if it's capable of putting-out more at 4 or 2-Ohms. And just in-general it's easier & more economical to get good performance without a transformer (of any kind). Full-range audio transformers are difficult and expensive to make, and power-output transformers even more so.

A million years ago I worked for a company that did 70.7 V constant-voltage installations for grocery stores and department stores, and sometimes small stadiums, etc. Most of the amps we had were tube amps and they had often additional transformer-taps for, 4, 8, 16-Ohms, and sometimes a 25V tap.

 

[patoulol]

I don't understand the point of this product. Why is it sold for so much? Is it better than another ncore 500?

 

[WestSideWarrior]

I don't understand the point of this product. Why is it sold for so much? Is it better than another ncore 500?

The "MI" range is targeted for home theater, distributed multi-zone audio or (probably?) bi-amp stereo use.

The module looks like stock NC500s, but other components are McIntosh custom designed (plus the glass front panel and blue meters), so there's McIntosh tax on top of that.

 

[patoulol]

Ah ok. Can we adjust the gain on the machine? Doesn't it buzz in the tweeters?

 

[Vacceo]

The "MI" range is targeted for home theater, distributed multi-zone audio or (probably?) bi-amp stereo use.

The module looks like stock NC500s, but other components are McIntosh custom designed (plus the glass front panel and blue meters), so there's McIntosh tax on top of that.

It's funny how it looks like "Mac but cheaper", yet their class D amps pack a performance as good if not better than their class AB.

 

[WestSideWarrior]

Ah ok. Can we adjust the gain on the machine? Doesn't it buzz in the tweeters?

Unfortunately, there is no gain adjustment knob on the unit.
The buzz (as in, hiss? white noise?) in the tweeters will likely depend on the sensitivity of your speakers. I did notice some very faint hiss when using the Klipsch speakers, but there were none on the Elac.

The unit's power supply may also buzz depending on your grid's quality and interference. There were some noticeable buzz during certain hours of the day, but the buzzing on my fluorescent lamp ballast is much more pronounced.

 

[patoulol]

Unfortunately, there is no gain adjustment knob on the unit.
The buzz (as in, hiss? white noise?) in the tweeters will likely depend on the sensitivity of your speakers. I did notice some very faint hiss when using the Klipsch speakers, but there were none on the Elac.

The unit's power supply may also buzz depending on your grid's quality and interference. There were some noticeable buzz during certain hours of the day, but the buzzing on my fluorescent lamp ballast is much more pronounced.

Yes, I had my old Purifi D-Class, I had buzz. I had to sell it and upgrade to a Crown Class D which doesn't have a power supply issue in the speakers (noticeable buzz).

The device's power supply also emits a small, high-pitched hiss sound at 1 meter

 

[patoulol]

@WestSideGuerrier

When your McIntosh MI254 is turned off, does it make a little coil/power hissing sound? You have to put your ear on the case.

 

[WestSideWarrior]

@WestSideGuerrier

When your McIntosh MI254 is turned off, does it make a little coil/power hissing sound? You have to put your ear on the case.

Unfortunately, the unit is in the cabinet so I won't be able to listen directly from on top of the case.
Listening from about 5cm from the front panel, there were no coil noise regardless of its power on/off state.

Although I do understand what you mean, since I have a Crown XLS1502 for sub duty and there was a very noticeable power supply coil whine at close proximity.

 

[Myaudio]

I ordered 2 of the McIntosh MI502. I realize it's an expensively packaged Hypex module.

They will drive passive subwoofers with no filters, so Power Guard and Sentry Monitor are welcome additions.

I already own other McIntosh amplifiers, so I accepted the premium over other Hypex-based amplifiers. I know I will enjoy the meters and monitor how much power my custom-built subwoofers draw.