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(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.
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.
Seems clean.
Seems, enough power.
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.
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.
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.
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.
20k Loopback
20k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2
L7 Audiolab Wolf style
22,4k Loopback
22.4k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2
22.4k 4 Ohm 5 W P501 SINAD
ASR standard style
40k Loopback
40k 4 Ohm 5 W P501 SINAD CH1 Loopback CH2
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.
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.)
22.4k 4 Ohm 5 W P501 Gain CH1 Loopback CH2
About 20.9 dB
Multitone Loopback
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.
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.
(https://www.audiosciencereview.com/.../boxem-arthur-4222-e1-amplifier-review.37930/)
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.
(https://www.audiosciencereview.com/.../boxem-arthur-4222-e1-amplifier-review.37930/)
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.
Last edited:
I promoted it to home page.
