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Marchaudio P422 Stereo Power Amplifier Renewed Review

thin bLue

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After massive failure with my previous review(https://audiosciencereview.com/foru...dio-p422-stereo-power-amplifier-review.35969/), I got great technical supports from ASR, Speaker gallery of DC inside, E1DA Discord Channel(@IVX, @staticV3 ) and Marchaudio.
(Detail for the appearance, see previous review post.)

Disclaimer
This is a review and undetailed measurements of the Marchaudio P422 stereo class D power amplifier. It is on kind loan from myself and costs US $1,988.68(P422 $1,675.21 + shipping to South Korea $132.68 + import tax $180.79) as previous

But this time, Marchaudio sent one low power reference load for free.
As 3rd party reviewer, I absolutely guarantee that there was no ask of change direction of review, and the supports has no influence on the review.

P422 is Purifi 1ET400A based amp with custom designed Power supply and buffer board.

Conditions
1662711324.jpg

Eventually, with AUX-0040 Filter!

and B series APx525 analyzer with AG52 as previous.

When AP connected to Class-D AMP without filter, AP can not fix suitably level, you can hear endless clicking sounds of relays.

Class-D produce signal at switching frequency(far above target measurement frequency range) so AP can't measure them. <- what I've experienced and got bunch of advices from ASR, Marchaudio

that's why I add low noise high linearity low pass filter like AUX-0040

BUT, If you are normal user, YOU NEED TO KNOW that frequency of switching is so high so that signal has no acoustic influence. Of course don't need pricey filters too.
You can simply take them as just AP's issue at all.

Also, Signal chain for the measurement has improved.
APx525 Output - Measurement Target Amp - AUX-0040 Filter - APx525 Input

And the loads
1662711343.jpg
1662711359.jpg
1662711373.jpg

last time, we saw magnificent non-linearity from low heat capacity load.

This time, I got 8 x 1000 W 16 Ohms

to build
2 Ch 4000 W 4 Ohms
1 Ch 8000 W 2 Ohms
loads.

To validate new dummies

1662711384.jpg
1662711399.jpg

I compared them with Reference load from March audio.

You can check the load in the lower right corner of the photo.

Let's see.

AP self SNIAD 20K.PNG

APx525 Output - AUX-0040 Filter - APx525 Input
Self check.

Filter works fine.

It shows the limitation of the analyzer.
Near to 109 dB we can't see certainty, Just can encounter huge errors.

so above 100 dB, I can say "We are looking at the measuring equipment itself, not the characteristics of the subject."
that case Actual values can be as good as a few dB or more.

BTW, I have to say sorry about FFT
I should display FFT window with dBrA(peak at 0 dB) not dBV(1 kHz peak is not at 0 dB).
Sorry for the inconvenience.

5 W 4 ohm 20k.PNG

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven
5 W 4 ohm 20k_March's reference load_Ch1.PNG

5 W 4 Ohm
P422 amp, March's reference load Ch 1, New Load Ch 2 4 Ohm both Ch driven

We can read this result as
1.March's reference load works slightly better than new loads but still reliable.
2.P422 Amp's performance is above APx525 analyzer(We are almost seeing AP itself).
3.P422 Amp has SINAD least over 105dB, I can make vague estimate about 106 to 107 dB(Need for Apx555/Other high-resolution DAC and ADC).

But this high SINAD, you can't hear any THD+N with that hot 1kHz signal, even at the 0dB Ideal full-band 0dB anechoic chamber.
Nowadays, many of well designed electronics are way beyond human hearing.
5 W 4 ohm gain.png

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven

the Gain
customized spec.
welcome to flat world.
5 W 4 ohm fr.png

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven

Frequency response
Can you see?

5 W 4 ohm fr large.png


Look at the scale
Even with 0.1 dB almost no deviation flaaaaaaaaaaaaaaaaaaat.
5 W 4 ohm cross talk.PNG

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven

Cross talk
Meaningless!
5 W 4 ohm cross-cross talk.PNG

5 W 4 Ohm
P422 amp, New Load, 4 Ohm

Cross-Cross talk
changed Ch 1 and Ch 2
Meaningless! x 2
5 W 4 ohm cross talk appended.PNG


5 W 4 Ohm
P422 amp, New Load, 4 Ohm

Many of Crosstalk
changed Ch 1 and Ch 2 and so son
Meaningless! x 3

It's not P422 AMP's Crosstalk
It's load and analyzers Crosstalk

Again, P422 Amp's performance is above the analyzer+load chaine.


We could only check P422 has normal crosstalk, It indicates that it was made normally(without problem = fine).

IMHO, P422 has very well suppressed crosstalk.

5 W 4 ohm multitone.PNG

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven

Multitone with dBrA

WOW, look great!

wait, did you see?
My mistake, Averages was only 1 instead of 8.
What a shame.

Floor could be much lower. I'll add multitone Averages : 8 next update.

5 W 4 ohm multitone dBV.png

5 W 4 Ohm
P422 amp, New Load, 4 Ohm both Ch driven

Same Multitone with dBV
It's cumbersome to look at because the position of peak is not 0dB.

I did same thing all above this. SORRY!

Finally

Main Dish for Power amp measurements

purifi.png
1ET400A.png
1ET400A levels.png



This is the spec sheet for the Purifi 1ET400A EIGENTAKT amplifier unit.
Since the P422 is made based on this unit, the better the power supply and buffer board are made, the closer to the above performance results,
The worse the performance, the worse the results will be.

to Read this graph(level sweep)
-The higher the worse.(THD+N ratio)
-The farther to the right is the higher the output.(Output Power)

When the output is very low, the signal itself is so small that it is affected by external factors, so it shows a rather high noise + distortion ratio. As the output gradually increases, the signal strength becomes stronger, the purity(in this case, relative strength of the signal = how low the THD+N ratio) increases. To borrow @PeteL 's words "sum of noise and distortion don't increase as fast as the signal level."

Then when it finally reached to output limits, the noise and distortion increase rapid and sharp so do noise + distortion ratio.

A very tight standard takes the performance as the effective output until the point where the sudden increase in noise & distortion begins (the inflection point)
As a general industry standard 1% (little loose), and for audio, 0.1% is used as a standard.


THD+N Ratio value of lowest point depends on performance limitation of analyzer, so pay attention to the location of the inflection point and the power(level).

with impedance
-The lower, the harder to drive.
Amp need to pump more current to load.

-The higher, the easier to drive.
Amp do not need to pump much current to load.

Then let's see P422 @ 4 Ohm

4 ohm level sweep.PNG


Look nice.
Let's compare.

4 ohm level sweep.PNG

Benchmark AHB2 Amplifier Power at 4 Ohm compared to Hypex NC400 Audio Measurements.png


Way higher output than Benchmark AHB 2

4 ohm level sweep.PNG

AUDIOPHONICS HPA-S400ET Measurements Low Gain Power into 4 ohm Balanced Purifi Stereo Amplifier.png


Audiophonics HPA-S400ET shows almost identical value.
Both amp did a nice job.

4 ohm level sweep.PNG

THDN-Ratio-vs-Measured-Level-4Ω.jpg



Lm Audio MIN400A shows a little quick rise than P422, HPA-S400ET.
It appears to be suffering from Power supply units limitation.

I know, all of us don't wanna see boring 4 Ohms.
2 Ohms for real!

2 ohm level sweep.PNG


P422 amp, New Load, 2 Ohm single Ch driven
???!

What?
2 ohm level sweep large.png



Almost 460 W of Clean Pure Power at 2 Ohms!
460 W is just an inflection point!!!!!

@ 0.1% 515 W - 527 W ??!
@ 1% 554 W - 576 W ????!?!

AWESOME!
Power supply did great job!
We can't get closer to amp units limits before Reach power supply's limits with both Ch driven(1000 W rated, but in fact the PSU can handle 1100 W well).

Even with KEF R3, this amp can handle them with ease.

Chosen_style_golf.jpg

I'm happy to recommend the Marchaudio P422 Stereo Amplifier.

Although the performance of my measuring equipment was insufficient, so I could not completely measure the amplifier that exceeded the equipment performance, but I could see that the performance of the P422 amplifier was equal to or exceeded that of the APx525 analyzer.

Again, there were some obvious mistakes, but since it is not too difficult to judge the overall performance, I think this measurement is very valid.

I will continue to improve our measuring procedures and equipment, and really honored to post my first valid review. It would not have been possible without the support of the 'DC inside speaker gallery' members who fully supported me and the strong technical supports from ASR members, and I would like to express my special thanks to March Audio for providing the reference dummy load.

(before measurements)Meaningless subjective assessment with my own iron ears(Just cry).

It sound like crystal clear.
and I close my eyes, soon It disappears into the air feels like amp doesn't exist.

Even Otaku-music(hard to drive), it drives well.

(After measurements)
If you have P422, you can hear crystal clear Otaku music with endless cry
 
Last edited:

Matias

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Nice, thanks!
 
OP
thin bLue

thin bLue

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Hello, I have a question

I didn't see the post very carefully but, seeying this.. why the peak at 3khz is that high?
index.php


As i remember, that peak is very very small (?)
index.php



Ty
Nice feedback.

That's exactly why I wrote this!

"BTW, I have to say sorry about FFT
I should display FFT window with dBrA(peak at 0 dB) not dBV(1 kHz peak is not at 0 dB).
Sorry for the inconvenience."
 

BrokenEnglishGuy

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Nice feedback.

That's exactly why I wrote this!

"BTW, I have to say sorry about FFT
I should display FFT window with dBrA(peak at 0 dB) not dBV(1 kHz peak is not at 0 dB).
Sorry for the inconvenience."
No no, sorry. To be honest i'm not in the position for even give you a feedback, just a question. I lack the knowledge..

Thank you :)
 

amirm

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Hello, I have a question

I didn't see the post very carefully but, seeying this.. why the peak at 3khz is that high?
Top of the graph is -40 dB whereas I use +5 dB. This stretches the bottom of the graph making distortion spikes far more pronounced than they are. The other reason is not using dB relative so every spike is referenced to 0 dB and not some other value.
 

amirm

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Floor could be much lower. I'll add multitone Averages : 8 next update.

5 W 4 ohm multitone dBV.png
On Multitone, I limit the graph/FFT to the actual frequency range of the test tone which is 20 to 20 kHz. That gets rid of the strange parts before and after in your measurement. In addition, FFT points will be better utilized for the actual audible range than wasted in ultrasonics. This lowers the effect noise floor a bit, making it more comparable to my test parameters.
 
OP
thin bLue

thin bLue

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On Multitone, I limit the graph/FFT to the actual frequency range of the test tone which is 20 to 20 kHz. That gets rid of the strange parts before and after in your measurement. In addition, FFT points will be better utilized for the actual audible range than wasted in ultrasonics. This lowers the effect noise floor a bit, making it more comparable to my test parameters.
Ah!
I'll add 20 to 20 kHz for comparability and broadband for additional info! Thanks Amirm!
 

SDC

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High waifu acceptance factor! People can enjoy crystal clear 2d to 3d soundstage conversion with these I bet!
 

beefkabob

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Excellent! Would you say this is almost as good as the ABH2 but a lot less money?
 

sweetchaos

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Excellent! Would you say this is almost as good as the ABH2 but a lot less money?
Does this answer your question?

NameTHD+N
(5W, 4 ohms)
SINAD (dB)
(5W, 4 ohms)
Power (W)
(1% THD+N, 4 ohms)
Price (USD)Source
Benchmark AHB2 (stereo)0.00023%1132103,000ASR
Benchmark AHB2 (mono)0.00026%1125006,000ASR
March Audio P4220.0006%1044001,625thin bLue

Courtesy of @Matias awesome spreadsheet.
 
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