I remember marketing literature from the late 80’s describing what appeared to be some feedback loop between the audio section and the SMPS (the DC-DC boost converter). Each manufacturer had their own version, described with fancy “audiophile” (unintelligible…) words. Being somewhat unique to high power car amp, could such feature explain the good distortion but poor crosstalk measurements?
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McIntosh MC 427 Amplifier Review
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audio_tony
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Back in my car audio repair days (1980's) I had the opportunity to try a few 'no name brand' amps (all Class AB) and when placed into a decent HiFi system, they actually sounded amazingly good.
I did reverse engineer one of them, and the amplifier topology was quite typical of a HiFi amp at the time, and they even used decent output transistors.
These amps were amazingly robust too, taking abuse in their stride (2 ohm loads etc.).
So I'm not surprised this McIntosh measures as well as it does.
I did reverse engineer one of them, and the amplifier topology was quite typical of a HiFi amp at the time, and they even used decent output transistors.
These amps were amazingly robust too, taking abuse in their stride (2 ohm loads etc.).
So I'm not surprised this McIntosh measures as well as it does.
AudioSceptic
Major Contributor
I'm not in the market for this but it's great to see something living up to, not abusing, the great name on it!This is a review and detailed measurements of the McIntosh MC 427 (MC427) stereo car audio amplifier. It is on kind loan from a member. It has been discontinued but used ones go for about US $500.
View attachment 331978
Not much to distinguish the amplifier from other car amps other than the bright blue logo. Unlike all the others I have tested though, this one is class AB, not Class D.
There are two small fans which I don't like to see. Fortunately in use the amp ran very cool, barely getting warm and I don't think the fans ever came on.
McIntosh MC427 Amplifier Measurement
As usual we start with our dashboard of 5 watts into 4 ohm load:
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Are you seeing what I am seeing? Distortion product at nearly -120 dB??? And in a car amp? Incredible. SINAD is noise limited and lands the MC427 neck and neck with a state of the art class D car amp:
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Notice the high current usage of 7 amps to produce 5+5 watts of power (nearly 100 watts in!). Noise performance is excellent for a car amplifier:
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Unlike most class D amplifiers, there is no load dependency in frequency response test:
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There is an offset between the two channels though and they roll off differently but this may be due to age.
Crosstalk is not great:
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It is similar to the last car amplifier I tested so there may be a common issue here with terminals they use or something like that.
Multitone performance is yet again excellent:
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Guess what 19+20 kHz intermodulation performance is:
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Yes, excellent.
Let's see if it meets the power spec of 100 watts per channel:
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Of course it does and then some. But better have good supply of current seeing how almost 40 amps were drawn.
Here is 8 ohm:
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Sweeping at different frequencies shows the class AB strength in not caring a lot but the amp did go into protection at lower frequencies:
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I was pushing it into clipping though which often causes that.
Finally, the amp was stable on power up other than a minor glitch:
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Conclusions
The MC427 delivers performance that is eye popping for a car audio amplifier. Distortion near -120 is insanely good, beating many home amplifier! Measured power exceeds specification. The only cost is much less efficiency.
This is really superb execution on behalf of McIntosh engineering. I don't know the merits of buying one used but the MC427 really shows how it is done.
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Erin doesn’t do measurements as well as Amir, but you can see that the McIntosh is “high end” for their true designs (Class AB products) as opposed to their lifestyle HypeX products.
The biggest problem, honestly, having owned several McIntosh products is
A) They will break if you ship them without factory packaging. The front panel is glass and it’s not any sort of fancy gorilla glass, etc. It’s not McIntosh’s fault, just that FedEx and UPS are more overworked than when USPS was shipping things back in the day.
B) If you ship them in factory packaging, it’s safe but it involves shipping on plywood slats. The boxes are super big which are actually too big for many small vehicles. They are also heavy and expensive to ship.
Yes, 0.0006% THD+N at the elbow = -104 dB. And that's at over 450 watts into 8 ohms. With a ton of headroom to boot.
Should have ignored it. Won't happen in use in a car!
Also, it should not have been allowed to bring SINAD or resolution down.
Otherwise, great, thanx.
Anton D
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Makes ya wonder why their high end stuff is tubed.How did they do it?
Do they know something?
DonR
Major Contributor
Yes, they know the marketplace and its customers.Makes ya wonder why their high end stuff is tubed.
Do they know something?
DonR
Major Contributor
Nothing from Maserati is worth thinking about since 1976.Would you buy a family van from Maserati?
I take that as No, then.
DonR
Major Contributor
That looks like a bit of a return to form and I appreciate that. For the money, I think a new Corvette could compete though and, of course, we have the "legendary" Maserati reliability and resale value.
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I seem to remember that McIntosh had teamed up with Clarion to develop its car products.
Makes ya wonder why their high end stuff is tubed.
Do they know something?
I owned the MC2102 which was really nice but sold it at the beginning of the pandemic. I miss it for the collectibility but in the grand scheme of things, my progression in audio has been a good one.
They are very candid that they make it because it sells:
McIntosh MC2102 power amplifier
"Larry—if I'd told you 10 years ago that McIntosh would be heavily into tubes in the 21st century, what would you have said?" "I'd have said you were crazy." I was talking with Larry Fish, McIntosh Laboratory's vice president of product planning. Larry's a solid-state man himself: more watts for...
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I guess my recollection about Clarion was correct!Impressive!
But expected.
Clarion owned McIntosh for a period before selling to D&M but McIntosh was still able to do the design. My understanding was that the head units were modified Clarion’s but the amps were McIntosh designs.
One thing to note is that the link I posted to their AVP at Erin’s Audio Corner is a “modified” Denon/Marantz product but it measured way better than anything we have seen from Denon and Marantz (at the time).
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