• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

NAD M28 7 Channel Purifi Amplifier Teardown

OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,395
Location
Seattle Area
Out of curiosity, is it possible that some of the same model amps test a point or two different from others? For example, is it possible that the M27 @amirm tested one of the better ones out of a batch? Seems like these all could vary a tad here and there.
Since I have tested 4 channels of this modular amp, I say the performance is what you expect in the rest of them.
 

Digital Mastering System

Active Member
Joined
Jan 3, 2020
Messages
142
Likes
170
Location
MN
Well, 3000h @85C is still acceptable if you don't intend to use the amp for more than 1-2 hours per day, although for how much it costs I do feel that 7-10 thousand hours @105C caps might be a better choice here.

http://www.lelon.com.tw/upload/prod/158140387342.pdf
Life for electrolytics doubles for every 10 degree C reduction in ambient temperature. I doubt the insides of this beast get much hotter than 55 degrees (too hot to touch). At 55 degrees these caps should last 24,000 hrs. At 45 degrees C (which to me seems more probable), these caps should last 48,000 hrs. That's 16.4 yrs. at 8 hrs a day.
 

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
3,303
Likes
3,838
:rolleyes:
Distinction without a difference to the intent of the original statement (sardonic humor) that seems to have been missed. Whatever you want to call it, they get a cut for every unit sold by NAD so they can save the world and so.. oh never mind.
No I got the joke, I'm not that dull. My point was meant to be informative. Not everyone knows that. It's the reason that in the blue range of the Sinad chart, we have 8 Hypex/Purifi based amp, and only one THX AAA based amp, different model.
 
Last edited:

restorer-john

Grand Contributor
Joined
Mar 1, 2018
Messages
12,580
Likes
38,281
Location
Gold Coast, Queensland, Australia
I would have expected better caps in a 5K product, that said if and when they fail they can be changed it's not heart surgery, can be done by any repair shop if out of warranty. Selling it at a 50% loss because of the caps is ridicolous.

What you don't understand is when SMPS capacitors fail, they can and do take out everything before them and stuff downstream as well, often very spectacularly. At a minimum you'll take out the mosfet drivers, switching ICs, perhaps the SMPS transformer itself and if the caps are on the secondary side, the control circuitry, buffers and even perhaps the amplifier modules themselves. It then become either a very expensive rebuild or simply a write off. How long will NAD keep a complete SMPS in parts stock and what will it cost? That's the question I'd be asking before plunking down my dosh on an otherwise excellently constructed amplifier.

It's much better to use the best capacitors you can at the time. There is zero excuse for crap capacitors in a so-called SOTA amplifier. I've spent decades replacing capacitors and let me tell you, the Nichicon, Nippon Chemicon, Rubycon, Panasonic and Elna are incredibly reliable when considered. It's the crap Chinese capacitors and the cheap early Taiwanese/Korean brands that are mostly just dreadful. Why use them at all? Your brand will suffer from premature failures that will cost more than the savings by far.

Japanese manufacturers never compromised with such things once you were in the upper echelons of their product ranges. Things have changed however and they aren't immune to it now.
 
Last edited:

Francis Vaughan

Addicted to Fun and Learning
Forum Donor
Joined
Dec 6, 2018
Messages
933
Likes
4,697
Location
Adelaide Australia
Failure of a SMPS can be catastrophic. I have a couple of Lexicon RV-8 AVRs I bought on eBay for peanuts. I bought them for the power amps. In both cases a tiny overheating failure in the control circuit of the low voltage SMPS used to run the digital and analog boards failed. It fried the entire system. Same fault in both units. What was once a very expensive high end AVR became instant unrepairable junk.
The design of the SMPS was a tiny bit unusual in the way this could occur, but it underlines the point. When they let go the cascading failure can be devastating. That there was no protection on the boards from what was a commodity SMPS was a bit disturbing. My gain I guess.
 

Michael YYZ

Member
Joined
Jul 12, 2020
Messages
52
Likes
27
Location
Toronto, Ontario
MCP6002 is also used in the M27.
9DA1B8E8-4FD9-41A7-9C9D-B223B6ACEDC2.png

It's for the audio signal detection for auto on/off, does the job, no need to spend more for this.
 

Michael YYZ

Member
Joined
Jul 12, 2020
Messages
52
Likes
27
Location
Toronto, Ontario
Honestly, it’s a bit disappointing that the M28 measured somewhat less than the M27. Nevertheless, I like my M28 very much.

I think we could agree that generally speaking, most for products being sold today, there is some truth to the fact that they don't last as long, and yes, we can see in a design like this some engineering choices that can potentially accelerate failures, but I think that going for the big conspiracy theories of pre planned obsolescence is a bit far fetch. Cost cutting measures, yes. Clearly, when you look at the mechanical assembly of this M28, it's clearly something made to be repaired, not disposable in an eventual failure. I believe that all manufacturers, except the the full cost no object, no compromise approach, all have to go trough their design, parts by parts and try to make it cheaper. This part is healty, it's much easier to make a design if you have zero cost restriction. Now yes cutting costs in a way that will not compromise performance beyond their specifications/performance goals, generally takes priority of extending the life span, True. but a company that don't make this exercice and just throw whatever is best and try to be competitive price wise will not survive. Still, this is not Apple here, this is Nad, Apple knows that when your phone is obsolete, you'll get another one. Nad knows that if their amps are unreliable, their reputation will suffer. Totally different. I'm not saying that they are immune to bad engineering choices, but they file it in the mistake drawer, It's not something they would want, to make your product die prematurely.
 

carlob

Addicted to Fun and Learning
Forum Donor
Joined
Aug 4, 2019
Messages
736
Likes
1,027
Location
Roma, Italy
What you don't understand is when SMPS capacitors fail, they can and do take out everything before them and stuff downstream as well, often very spectacularly. At a minimum you'll take out the mosfet drivers, switching ICs, perhaps the SMPS transformer itself and if the caps are on the secondary side, the control circuitry, buffers and even perhaps the amplifier modules themselves. It then become either a very expensive rebuild or simply a write off. How long will NAD keep a complete SMPS in parts stock and what will it cost? That's the question I'd be asking before plunking down my dosh on an otherwise excellently constructed amplifier.

It's much better to use the best capacitors you can at the time. There is zero excuse for crap capacitors in a so-called SOTA amplifier. I've spent decades replacing capacitors and let me tell you, the Nichicon, Nippon Chemicon, Rubycon, Panasonic and Elna are incredibly reliable when considered. Its's the crap Chinese capacitors and the cheap early Taiwanese/Korean brands that are mostly just dreadful. Why use them at all? Your brand will suffer from premature failures that will cost more than the savings by far.

Japanese manufacturers never compromised with such things once you were in the upper echelons of their product ranges. Things have changed however and they aren't immune to it now.

I understand that very well having repaired failed SMPS caps failures in a couple of my own amps (damage depends of the SPMS topology) but there are design tricks to extend the life of cheap caps and SMPS engineers know them, btw that is a very specific field. Also depends on the fault management that has been designed.
For a cheap cap core temperature rated 115C, the life would probably be around 2,000 hours or so. Imagine a computer SMPS which is on 24/24, 2000 hours suffice maybe for three months. You need 5 years so at least about 44,000 hours and still you have all kind of cheap capacitors inside pc SPMS. Good design or bad design, that's it. You really can't judge the design from a teardown pic.

It is really difficult to judge if you don't know in detail the circuit design, datasheets, have temperature multipliers been used or not, ripple etc. That said I personally don't like to see cheap elkos in expensive devices as I don't like to see Capxcons in a lot of Behringers or other cheap brands in Yamaha amps BUT still I would not sell a new 5K product at a 50% loss based on the caps brand. Maybe I wouldn't buy it but that's another matter.

This amp is perfectly repairable, even out of warranty. If carries a 3-years warranty right? If you are so concerned use it for 3 years and sell it after that.
 
Last edited:

kn0ppers

Active Member
Joined
Jul 4, 2019
Messages
192
Likes
258
Location
Germany
Having this thing recapped will cost you a pretty penny though.

I think you can't really compare this to PC power supplies that have a fan providing direct airflow, with usually a thermal probe on at least one of the heatsinks.
 

Daniel0

Member
Joined
Jul 3, 2020
Messages
80
Likes
44
The Hypex power supplies use cheap caps too. And they are a source of failures there.
I don't know about their reliability but at least they are pretty cheap and easily replaceable for years to come. And i suppose their future PSUs will be compatible with the old connectors too.
 
Last edited:

YSC

Major Contributor
Joined
Dec 31, 2019
Messages
3,194
Likes
2,570
I'm not gonna disagree with you with the fact that they should have better capacitors, but hey we live in a crazy world where some people have unlimited funds. Compagnies that are in the business of "luxury" sell their amps 100 000$ and use capacitors that are 200$ a pop. Not that anybody would need that, but that's luxury
well yea, the thing I think most ppl here in ASR just demand them to use some caps which is suitable for being stable and last quite some time and not this kind of cheaping out and sacrifice the longevity of a product, it;s just like buying a Mercedes with cheaped out engine bearing which will kill off the car and cost a forture to repair within reasonable usage time
 

Daniel0

Member
Joined
Jul 3, 2020
Messages
80
Likes
44
I think we could agree that generally speaking, most for products being sold today, there is some truth to the fact that they don't last as long, and yes, we can see in a design like this some engineering choices that can potentially accelerate failures, but I think that going for the big conspiracy theories of pre planned obsolescence is a bit far fetch.
I think you live in another world if you believe planned obsolescence is a conspiracy theory.
You should read some books/articles or watch some documentaries about that. You could say our current capitalistic economy relies heavily on planned obsolescence.
Of course there are some that tend to make more or less reliable products but in general you can see this everywhere.
https://en.wikipedia.org/wiki/Planned_obsolescence
 
Last edited:

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
3,303
Likes
3,838
I think you live in another world if you believe planned obsolescence is a conspiracy theory.
You should read some books/articles or watch some documentaries about that. You could say our current capitalistic economy relies heavily on planned obsolescence.
Of course there are some that tend to make more or less reliable products but in general you can see this everywhere.
https://en.wikipedia.org/wiki/Planned_obsolescence
I didn't say it didn't exist. I was talking about this amp, not about the capitalistic economy... I just tought that NAD wanted to cut cost, not a deliberate strategy to find ways to make sure the amp break.
 
Last edited:

MakeMineVinyl

Major Contributor
Joined
Jun 5, 2020
Messages
3,558
Likes
5,871
Location
Santa Fe, NM

Vasr

Major Contributor
Joined
Jun 27, 2020
Messages
1,409
Likes
1,923
I didn't say it didn't exist. I was talking about this amp, not about the capitalistic economy... I just tought that NAD wanted to cut cost, not a deliberate strategy to find ways to make sure the amp break.

Those aren't necessarily mutually exclusive, just saying. ;)

And then there are various shades of grey in-between those two (like supply chain considerations).

We won't know the intent unless we were an insider. We can only speculate based on biases for or against the brand to support a narrative.

What really matters is whether it can lead to early failures or not independent of the intent. It is a good thing people have come to know of this possibility from the tear-down. So, they can make informed choices.
 

RichB

Major Contributor
Forum Donor
Joined
May 24, 2019
Messages
1,946
Likes
2,611
Location
Massachusetts
I understand that very well having repaired failed SMPS caps failures in a couple of my own amps (damage depends of the SPMS topology) but there are design tricks to extend the life of cheap caps and SMPS engineers know them, btw that is a very specific field. Also depends on the fault management that has been designed.
For a cheap cap core temperature rated 115C, the life would probably be around 2,000 hours or so. Imagine a computer SMPS which is on 24/24, 2000 hours suffice maybe for three months. You need 5 years so at least about 44,000 hours and still you have all kind of cheap capacitors inside pc SPMS. Good design or bad design, that's it. You really can't judge the design from a teardown pic.

It is really difficult to judge if you don't know in detail the circuit design, datasheets, have temperature multipliers been used or not, ripple etc. That said I personally don't like to see cheap elkos in expensive devices as I don't like to see Capxcons in a lot of Behringers or other cheap brands in Yamaha amps BUT still I would not sell a new 5K product at a 50% loss based on the caps brand. Maybe I wouldn't buy it but that's another matter.

This amp is perfectly repairable, even out of warranty. If carries a 3-years warranty right? If you are so concerned use it for 3 years and sell it after that.

Can such failures blow speakers?

- Rich
 
Top Bottom