NAD M28 Seven Channel Power Amplifier Review

[miero]

It might not be the same module:

The Masters M28 uses Eigentakt™ amplifier technology, manufactured by NAD in license from Purifi.

Source: https://nadelectronics.com/product/m28-seven-channel-power-amplifier/

 

[pma]

With a different PCB layout. Enough to make a difference.

 

[carlob]

If you are willing to live with three boxes you can purchase two 3-channels Purifi amps and one monoblock. Now a better question would be: who needs 7 channels of Purifi?

For example I have a 5.2.4 system so I need 9 amps, you can go with 9 channels Purifi but it would be overkill as I doubt that the height speakers and maybe the surrounds need that much power+quality. Probably in my situation I could do with a 3-channel Purifi for LCR, and lower power Hypex modules for the other 6 channels...

 

[Vasr]

Not sure if the price is at a premium. Take a typical 20 percent off NAD msrp and that gets you about $571 a channel. Not bad even with these tests, no?

Compared to what? An ATI hypex at an equivalent street price of less than $3400 for seven channels? You are paying a premium for the new modules' potential without it being realized in an implementation (let alone in any audible difference).

 

[HTNut1975]

Compared to what? An ATI hypex at an equivalent street price of less than $3400 for seven channels? You are paying a premium for the new modules' potential without it being realized in an implementation (let alone in any audible difference).

Compared to any iteration of any Purifi amp on the market.

 

[PeteL]

Distortion.

Not sure I understand, the rise of distortion, is due to loading or ground issues or both?

 

[Vasr]

Compared to any iteration of any Purifi amp on the market.

You are sounding like a NAD salesman now. Which Purifi multi-channel amp is available? With your logic, a 7 channel Class AB per channel should be comparable to a per channel cost of a comparable stereo Class AB? Doesn't work that way.

That is the very definition of paying a price premium for the latest (but not the greatest) and the first on the market. Don't conflate premium with high. The latter is subjective depending on one's definition of pocket change.

Like I said before, if you want the bragging rights for the first kid on the block with a Purifi in a multi-channel and/or the aesthetics, one can certainly want to pay a premium for it. But to conflate it with the performance of the reference implementation when it fails to meet it and seems to provide no audible benefits over a previous model seems more hype than substance to me.

 

[Vasr]

Not sure I understand, the rise of distortion, is due to loading or ground issues or both?

Hey, I am no electronics wizard and I can't evaluate the technical correctness of the assessment but the explanation seemed clear to me. There is a graph in the measurements that shows rise in distortion with power level before clipping. This means that the distortion is correlated with loading (of the circuits). An explanation for that kind of behavior is a grounding issue.

 

[Chromatischism]

Now a better question would be: who needs 7 channels of Purifi?

No one. Just get NCore and call it good. Or Stereo Purifi for the left and right, NCore for the rest.

 

[HTNut1975]

You are sounding like a NAD salesman now. Which Purifi multi-channel amp is available? With your logic, a 7 channel Class AB per channel should be comparable to a per channel cost of a comparable stereo Class AB? Doesn't work that way.

That is the very definition of paying a price premium for the latest (but not the greatest) and the first on the market. Don't conflate premium with high. The latter is subjective depending on one's definition of pocket change.

Like I said before, if you want the bragging rights for the first kid on the block with a Purifi in a multi-channel and/or the aesthetics, one can certainly want to pay a premium for it. But to conflate it with the performance of the reference implementation when it fails to meet it and seems to provide no audible benefits over a previous model seems more hype than substance to me.

When you need more than two channels, cost does work that way. I'm not an NAD salesperson--just explaining the logic of cost and getting multiple purifi amps for a surround system. You seem to be saying that the cost is at a "premium" because Purifi is the newer kid on the block, but my point is that it doesn't seem all that much of a premium--what modules are in the ATI? Are those prices at a premium? How long have those modules been out? The price difference is not that much between the Purifi iteration of the NAD and the nc400 iteration found in the ATI.

 

[pma]

Not sure I understand, the rise of distortion, is due to loading or ground issues or both?

https://www.allaboutcircuits.com/te...sing-harmonic-distortion-in-audio-amplifiers/

Look at rail decoupling distortion and induction distortion. It is not trivial to explain, you need to work with.

 

[Vasr]

When you need more than two channels, cost does work that way. I'm not an NAD salesperson--just explaining the logic of cost and getting multiple purifi amps for a surround system. You seem to be saying that the cost is at a "premium" because Purifi is the newer kid on the block, but my point is that it doesn't seem all that much of a premium--what modules are in the ATI? Are those prices at a premium? How long have those modules been out? The price difference is not that much between the Purifi iteration of the NAD and the nc400 iteration found in the ATI.

This is getting silly with "not all that much of a premium". You are either pregnant or you are not. So I will stop with this.

If you look at any line with the ability to add more channels in Class AB or Class D, the per channel price of a module is always cheaper as you go up in channels. Because there are fixed costs in a chassis and a power supply and packaging and marketing that does not scale down proportionately if you have less channels. This is how it works with the ATI line for example where you can get anything from 2-8 channels in a configuration.

You are using the cost of an equivalent configuration using stereo amps (let us ignore for now whether they are as deficient in implementation as the NAD) or monoblocks and justifying this way. It has never worked like this for people who buy multi-channel amps.

Seems like a lot of rationalization for a piece of metal and plastic and glass.

 

[JohnYang1997]

Not sure I understand, the rise of distortion, is due to loading or ground issues or both?

Loading -> current flowing through ground -> increased ground differences -> distortion

Loading part is obvious but the followings are suspecting.

 

[HTNut1975]

@Vasr I understand the point about the cost of the two channel vs multichannel. I get it. What I don’t get is what you mean by “at a premium” as if this is priced well beyond any iteration of a Purifi amp (and for that matter, as if it were extraordinarily higher than the price of any iteration of a multichannel nc400 or nc500 or sets of nc400 or nc500 multichannel amps to get to seven channels). Pick any combination you like in the blue category and I’d be happy to compare prices and market value and what we would likely be able to sell these units for, say, three years from now.

 

[PeteL]

Loading -> current flowing through ground -> increased ground differences -> distortion

Loading part is obvious but the followings are suspecting.

Thanks for making it clearer, I have to say that english is not my first language and I don't really use loading in this context, but since in the review Amir link this increased distortion to the higher gain of the buffer, I interpreted "loading" simply by the definition of applying a voltage to a load, in this particular case, a higher voltage than the reference design, that was for me the "obvious" part. Of course ground return currents are undesirable, but thanks for clarifying your point.

 

[JohnYang1997]

Thanks for making it clearer, I have to say that english is not my first language and I don't really use loading in this context, but since in the review Amir link this increased distortion to the higher gain of the buffer, I interpreted "loading" simply by the definition of applying a voltage to a load, in this particular case, a higher voltage than the reference design, that was for me the "obvious" part. Of course ground return currents are undesirable, but thanks for clarifying your point.

With 4ohm, the amp has higher distortion vs power. That's why I call it because of loading. And you are definitely correct. But loading can mean a lot of things. The return current may not cause issue if designed better.

 

[PeteL]

https://www.allaboutcircuits.com/te...sing-harmonic-distortion-in-audio-amplifiers/

Look at rail decoupling distortion and induction distortion. It is not trivial to explain, you need to work with.

Thanks, Yes I get this. I just misinterpreted the loading term.

 

[PeteL]

You are sounding like a NAD salesman now. Which Purifi multi-channel amp is available? With your logic, a 7 channel Class AB per channel should be comparable to a per channel cost of a comparable stereo Class AB? Doesn't work that way.

That is the very definition of paying a price premium for the latest (but not the greatest) and the first on the market. Don't conflate premium with high. The latter is subjective depending on one's definition of pocket change.

Like I said before, if you want the bragging rights for the first kid on the block with a Purifi in a multi-channel and/or the aesthetics, one can certainly want to pay a premium for it. But to conflate it with the performance of the reference implementation when it fails to meet it and seems to provide no audible benefits over a previous model seems more hype than substance to me.

In the end there will be no answer to this debate until other manufacturers do competitive products, then we'll know A if they can offer it for cheaper, and B if they can beat these specs, in the mean time it's just hypothetical. Or yes we can look at it differently and argue that a 7 channel amp from monoprice is objectively a better deal, yes, the law of diminishing return apply.

 

[eduardw]

Hi Any guess how the NAD C298 will compare to the reference model. Before the test results I was leaning towards buying the Nad C298. But now I do not know. Maybe I just need to be patience and wait for the first test results.

 

[Vasr]

In the end there will be no answer to this debate until other manufacturers do competitive products, then we'll know A if they can offer it for cheaper, and B if they can beat these specs, in the mean time it's just hypothetical. Or yes we can look at it differently and argue that a 7 channel amp from monoprice is objectively a better deal, yes, the law of diminishing return apply.

Fully agree.

There are a few things NAD has done very well here, all in marketing. I just wish they had done as good a job in engineering. I just hate to reward companies that don't and rely more on hype and marketing. The more your reward them, the more they do that.

I wonder if they hired a marketing executive from Apple or a sneaker company or a toothbrush company because that is the model they are following in product marketing.

First, jumping on the latest Class D model is a good move for pricing power. Separates the initial adopters that get excited about the latest from their wallets easily. Second, most of the competition in Class D right now are small boutique players and a multi-channel amp just does not have a big enough market for their meager marketing budget to make developing one economically feasible. NAD on the other hand, has the brand power and marketing reach to position it for that multi-channel separates market even if it is not high volume. This is positioned to sell along with their pre/pros and so it is a leveraged ecosystem play rather than just a market for a separate amp. They are getting more and more into life-style market segment and so wise to bring in an external design team for the exterior. It works. They don't have to compromise on the engineering but they do because marketing and hype works. This is what kills me.