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Marchaudio P501 Mono Block Power Amplifier Review

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thin bLue

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P501-front-angle-above-view.jpg

(Photo from Marchaudio)

I saw some of ASR members request about review this Amp.
And for my personal curiosity I asked to Company to lend one for review. After I finished measurement, I asked company how to return. But the Company gave me right to dispose of it.

Disclaimer
This is a review and undetailed measurements of the Marchaudio P501 Mono Block Class D power amplifier. It was sent to me by the company, free of charge.
Otherwise, the company has no influence over the review, and I myself have consistently maintained my credibility as a third-party reviewer.

let's look at the data of the makers.

P501 Amp is based on Purifi 1ET7040SA
70 Means 70 V of rail power, 40 Means 40 A of Max output current.

1ET7040SA.PNG


1ET7040SA-2.PNG

1ET7040SA-4.PNG

Through the datasheet, we can guess. If Power supply unit don't feed appropriate voltage around 70 V to 1ET7040SA, you won't get a high enough output compared to 1ET400A.
If we choose to use 1ET7040SA(~14μV(A)), even though 1ET400A has lower noise(~11.5μV(A)) and lower price, we must be able to get enough benefits(the Output power) for justification.

Then, we can look Marchaudio's in house data.
P501-1-1.PNG
다운로드 (2).png

Seems clean.

P501-1-2.PNG

다운로드 (1).png

Seems, enough power.
image009.png

DC offset looks clean too.
Normally, 50 to 150 mVDC is called difficult to detect aurally, and 10 to 20 mVDC is considered harmless and unavoidable.
The output DC offset voltage shows 0.22 mVDC, which is simply negligible.

It is also stated on the Purifi's data sheet that 1ET7040SA has a DC offset of less than 10 mVDC.

1ET7040SA-3.PNG


For Before looking at the measurements, let's briefly talk about the buffer board for better understanding.
Purifi-based amplifiers are largely composed of four elements.
1. Enclosure, the box
2. Purifi amplifier unit itself
3. Power supply unit (PSU) that feeds power to the Purifi amplifier unit
4. Buffer board that receives external signals, processes them appropriately, and passes them to Purifi amplifier unit

What kind of signal processing does the buffer board do?
First, Gain. The final gain of the complete amplifier (=buffer board gain + Purifi unit's fixed gain) determined by how the buffer board is configured.

20221118_164211.jpg

This case, each gain is configured to push the amplifier maximum output with standard balanced input 4 Vrms and standard unbalanced input 2 Vrms. At 20.5dB, if you put a 4Vrms signal, reach the maximum output of the amplifier.


Unlike the product I reviewed, now they offers two individual gain + added an external gain selector, and accept order with personalised gain if customer wish to connect amplifier to devices with various output voltage range.
P501-1.PNG



In addition, the buffer board plays an important role in addition to simple gain.
This is because the OP-AMP of the buffer board not only provides amplification but also rejects the common mode by processing the balanced signal.
In other words, it cancels the signal that comes along the + signal line and the - signal line at the same time (= noise = common mode).
OP-AMP amplifies the difference (differential gain -> infinite) when different things (differential signals) come into each signal lines, while
When the same thing comes in (common mode) both lines, the gain becomes 0 (common mode gain) and nothing goes out. (Gain = Output/Input)
This active common mode rejection is not achieved by a change in impedance. It's game of gain difference.

It is important that the OP-AMP has less self noise because it cancels outer noise and amplifies the signal in the middle of the signal chain.
In particular, a buffer board for Class-D amplifier like Purifi must have low noise in the high-frequency band. For that purpose, the voltage of the power supply entering the buffer board and OP-AMP must be very constant, so a precise voltage regulator with high fidelity must be inserted.

In addition, OP-AMP has limitation. How well the OP-AMP rejects the common mode is called CMRR (Common Mode Rejection Ratio). But CMMR drastically drops at certain high-frequency range. Over this range, OP-AMP cannot reject noise meaningful any more.
Class-D amplifiers such as Purifi can produce significant IMD when high-frequency ingredients come in, so it is necessary to block high-frequency noises. So, the RF filter must be on the input terminal (not exactly the buffer board, but the RF filter placed at the input terminal, then connected to the buffer board).

RF filter can reduce input impedance of complete amplifier.
Even so, the input impedance of about 40 kOhm is guaranteed with well designed RF filter, and it is a value that cannot cause any problems when directly connected to a DAC these days.
(If driving problems occur at this input impedance, the preamplifier/DAC is really poorly designed.)

The use of adding resistors to compensate for this input impedance reduction adds Johnson noise(the more resistance, the more thermal noise increase) and forms additional output DC offset(causes pop noise), so it is recommended to avoid it unless absolutely necessary.


Finally, the Data.
APx525B loop back 20k with 0040 filter.PNG

20k Loopback

Marchaudio P501 SINAD 20k APx525B XLR loop back 4 ohms 5 w.PNG

20k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2

Marchaudio P501 SINAD 20k 4 ohms 5 w.PNG
20k 4 Ohm 5 W P501 SINAD
L7 Audiolab Wolf style

APx525B loop back 22.4k with 0040 filter.PNG

22,4k Loopback

Marchaudio P501 SINAD 22.4k APx525B XLR loop back 4 ohms 5 w.PNG

22.4k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2

Marchaudio P501 SINAD 22.4k 4 ohms 5 w.PNG

22.4k 4 Ohm 5 W P501 SINAD
ASR standard style

APx525B loop back 40k with 0040 filter.PNG

40k Loopback

Marchaudio P501 SINAD 40k APx525B XLR loop back 4 ohms 5 w.PNG

40k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2

Marchaudio P501 SINAD 40k 4 ohms 5 w.PNG

40k 4 Ohm 5 W P501 SINAD
Broad Band

As you can see 20k, 22.4k 40k data, it is too close to the limits of the APx525B analyzer to get a good reading. P501 has very good performance. Real values could be at least a few dB better.
It is considered consistent with the company's in-house measurements.

EDIT : Data with loopback, I forgot to set FFT window to dBrA. sorry for inconvenience.


Marchaudio P501 FR TRS APx525B loop back 22.4k 4 ohms 5 w.PNG

22.4k 4 Ohm 5 W P501 FR CH1 Loopback CH2

Textbook perfect. (Increase in lower end is software error. ANY of that LF deviation dose not exist.)

Marchaudio P501 GAIN 22.4k APx525B XLR loop back 4 ohms 5 w.PNG

22.4k 4 Ohm 5 W P501 Gain CH1 Loopback CH2
About 20.9 dB
Multitone TRS APx525B loop back.PNG

Multitone Loopback

Marchaudio P501 Multitone TRS APx525B loop back 22.4k 4 ohms 5 w.PNG

4 Ohm 5 W P501 Multitone CH1 Loopback CH2
Considering about 20.9 dB of gain, you could see how close the P501 is to the performance of the analyzer. This analyzer is not suitable for measuring the absolute value of this amplifier's performance.


Marchaudio P501 Power sweep 4 ohms.PNG

4 Ohm P501 Power sweep
4 Vrms input produces about 487 W @ 1% ( 487.3 W @ 1.027% )
Although there are some differences, it shows a tendency that is sufficiently similar to the measurement results provided by the company.
You can compare this to another Purifi 1ET7040SA based amplifier yourself.
BoXem Arthur 4222E1 Monoblock Amplifier Power into 4 ohm Measurement.png

(https://www.audiosciencereview.com/.../boxem-arthur-4222-e1-amplifier-review.37930/)


Marchaudio P501 Power sweep 2 ohms.PNG

2 Ohm P501 Power sweep
4 Vrms input produces Near 1 kW @ 1% ( 0.971 kW @ 1.048% )
Although there are some differences, it shows a tendency that is sufficiently similar to the measurement results provided by the company.
You can directly compare this to another Purifi 1ET7040SA based amplifier again.
BoXem Arthur 4222E1 Monoblock Amplifier Power into 2 ohm Measurement.png

(https://www.audiosciencereview.com/.../boxem-arthur-4222-e1-amplifier-review.37930/)



8814dac4efb3f6daf47b6f4c5f67601f.jpg


Conclusions
Full realization of Purifi amplifier module’s performance. Near 1 kW of full power can be easily achieved with standard device’s output voltage.
Thanks to Its efficiency, under normal use, stay cool with use, yet producing massive driving power. It doesn’t go above warm, never gets hot.

My pleasure to recommend Marchaudio P501 Mono Block Class D power amplifier.
 
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EdW

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Another example of superb engineering from March Audio realised by great attention to detail. Alan March’s choice of power supply, rather than the standard Hypex unit, has enabled the full Purifi data sheet to be met. Just as he did with the P422.

EDIT to correct minor typo
 
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amirm

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Like the one Amir does for DAC's.
Switching amps make this test hard to run as the harmonics get mixed up with noise-shaping of class D amps. You would have to run it with much lower bandwidth in which case you get false results for frequencies above 10 kHz (it would step down which is wrong).
 

Sokel

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Switching amps make this test hard to run as the harmonics get mixed up with noise-shaping of class D amps. You would have to run it with much lower bandwidth in which case you get false results for frequencies above 10 kHz (it would step down which is wrong).
20Hz-1000Hz would be enough for me,it's the low's and mid's I'm curious about.
 
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thin bLue

thin bLue

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Switching amps make this test hard to run as the harmonics get mixed up with noise-shaping of class D amps. You would have to run it with much lower bandwidth in which case you get false results for frequencies above 10 kHz (it would step down which is wrong).
Great point! It helps me a lot!
Great work as always. Your formatting has improved much. :) I promoted it to home page.
My pleasure! Thank you very much!
 
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thin bLue

thin bLue

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20Hz-1000Hz would be enough for me,it's the low's and mid's I'm curious about.
I should make various range data sets for you!
Let's see what can we get together!
 

boXem

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A few questions:

1. How did you manage to access confidential information (the 1ET7040SA spec) from Purifi?

2. Knowing that the 1ET7040SA efficiency in 2 Ohm at 1kW is around 92%, it needs 1.1 kW to output 1 kW. How is it possible with a 1 kW power supply?

3. Are you sure that your 2 Ohm load actually measures 2 Ohm when heavily heated ?

4. In order to stick with ASR policy, could you please measure the max power at distortion corner, not at 1%?
 

fordiebianco

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Thank you for this. Good to see that March Audio continues to deliver (for amps).
 
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thin bLue

thin bLue

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A few questions:

1. How did you manage to access confidential information (the 1ET7040SA spec) from Purifi?

2. Knowing that the 1ET7040SA efficiency in 2 Ohm at 1kW is around 92%, it needs 1.1 kW to output 1 kW. How is it possible with a 1 kW power supply?

3. Are you sure that your 2 Ohm load actually measures 2 Ohm when heavily heated ?

4. In order to stick with ASR policy, could you please measure the max power at distortion corner, not at 1%?

1.You can find it easily on ASR

Screenshot_20221202-185533_Chrome.png



2.That power is what I observed with my dummy loads and Analyser. I'm not a maker.

But, this image could be help you.
20221118_164253.jpg


3. My load is rated as 8 kW.
And it stayed Cold, Start to the End.
And I explained about measurement conditions in detail previously ( https://www.audiosciencereview.com/...-stereo-power-amplifier-renewed-review.37267/ ). So your comments 3. feels quite rude to me.

4. Anyone can read graph and find cut-off point they want to use. That's why I upload Data with full details not just graph. Anyway thanks for suggestions.
 
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