March Audio P122 Class D Amplifier Measurements

[MZKM]

although I just wish a "line-in-the-sand" %THD figure was used for ASR tests going forward. I use 0.1%, Hypex uses 1%, Amir uses the "knee" which could be essentially anything and varies from product to product.

Stereophile uses 1%.

Now, from the informal testing I have seen, 1% system THD in the treble is about the threshold of audibility with various types of music playing. To account for multiple links in the system chain and a safety net, I personally look at 0.1% THD.

 

[tmtomh]

I think many of us would like to have a consistent power rating at a THD level below 1%.

So if @amirm would be willing, I personally would be grateful if he could list two standardized power rating figures: one at 1% THD, and another one at some agreed-upon lower level that provides more "buffer" from the audibility threshold - perhaps 0.05%?

If others think this is dumb, I am happy to revise my position here. But for now, that's my $.02.

Thanks!

 

[pma]

another one at some agreed-upon lower level that provides more "buffer" from the audibility threshold - perhaps 0.05%?

But this "audibility threshold" expressed as a single number is totally pointless if we do not know the spectrum of distortion and level. I think you know ear masking curves that show both frequency and level dependence of masking of harmonics as a function of tone frequency and level, right? Where is the single number there?

 

[amirm]

Is the right picture at full power? Text says 5W on both.

It is.

 

[amirm]

Was amp actually driving a resistor load with rated power during this test?

Yes.

 

[amirm]

Ok, let's hear what he will say. What strikes me as odd is why using 5W resistor when you have (say) 150W or 250W resistor to measure performance under load at full power.

5 watt is the amp output power not the load resistor. Same load resistor is used for all tests.

 

[maty]

March Audio P122, with Hypex NC122MP module and XLR inputs

IOM NCore Pro with Hypex NC252MP module and XLR inputs

I know, different modules. I get the impression that it is about the stereo module and not about its implementation as I thought at the beginning.

 

[AlexScan]

I guess you meant 252MP. You already have your answer here:

https://www.audiosciencereview.com/...d-measurements-of-iom-ncore-pro-pwr-amp.8979/

I tend to agree. (No offense, Alan). For EU customers, Audiophonics NC122MP or NC252MP amps are more competitive (if we don't consider build and finish).

No I speak for the NC250MP (mono version), according to Hypex datasheet better THD than the stereo one...

And you're right Nico from Audiophonics build good performance/price ratio product... the last amp Purifi stereo with home-made input board is the better exemple.

 

[AlexScan]

Our P252 performs better.

Why you tell that ?

You are a better version of the NC252MP module ? Better implementation ?

 

[Ron Texas]

Typical for amps based on this series of modules. It's kind of difficult to mess up putting an all on one board amp in a box. Probably not enough power for inefficient speakers in large rooms.

 

[spacevector]

Frequency response is good but not flat out to infinity as some amps are:

Was this qualified with simulated speaker load?

 

[VintageFlanker]

No I speak for the NC250MP (mono version), according to Hypex datasheet better THD than the stereo one...

Right. Except @March Audio doesn't make NC250MP units.

the last amp Purifi stereo with home-made input board is the better exemple.

Would be glad if @Audiophonics could send a unit, see if this home board doesn't change (down) the performance Vs reference. Still the cheapest Purifi offering around, tho.

 

[tmtomh]

But this "audibility threshold" expressed as a single number is totally pointless if we do not know the spectrum of distortion and level. I think you know ear masking curves that show both frequency and level dependence of masking of harmonics as a function of tone frequency and level, right? Where is the single number there?

You’re responding to the wrong person. I was commenting on where the standardized THD figure should be set. If you want to argue against the utility of any standardized figure, then your argument is with this entire line of discussion and everyone who’s participating - so kindly quote someone else’s comment (or start a new thread) to grind your borderline off-topic axe. Thanks.

 

[AlexScan]

Right. Except @March Audio doesn't make NC250MP units.

Would be glad if @Audiophonics could send a unit, see if this home board doesn't change (down) the performance Vs reference. Still the cheapest Purifi offering around, tho.

Yes but he have access to Hypex OEM program... I have to... but I not a professionnal and I am very "money limited"...

I can contact Audiophonics to tell you to send somme amp to Amir...

 

[gvl]

Are there less sexy amps with comparable performance at half the price?

 

[amirm]

The process for determining power at a set percentage is very stressful on the amplifier. The analyzer keeps hunting around trying to get to that near exact value, meanwhile pushing the amp into and out of clipping. It is also unreliable in that some amps simply can't go low enough in distortion. Even 1% THD+N causes problem with some amps and I have had to adjust that to 2% or even higher.

So for now, I like to stay where I am. The knee is the conservative assessment of the design limit of the amplifier. In a perfect world, every company would rate their amps this way and reviewers would measure the same way. A few watts lower or higher there is not material. Then, I have continuous and burst at 1% THD+N. Adding yet another test is more work and I am not sure it adds much value.

 

[VintageFlanker]

Are there less sexy amps with comparable performance at half the price?

This one.

 

[gvl]

This one.

Nice. The almost 20% tax isn't. Do you know if they waive it for US based purchasers?

 

[Sal1950]

Hi Sal
As Amir explained above he takes his measurement point at a lower distortion level than Hypex.

Yes thank you. That "might" have been mentioned in the original article? LOL

From the product page unless @March Audio has changed something:
Dimensions 330mm x 180mm x 75mm

What's that in "real" numbers???

 

[Koeitje]

What's that in "real" numbers???

3 carrots and a polliwog.