Marchaudio P501 Mono Block Power Amplifier Review

[Sokel]

Why do we need a single value to make a comparison? Look at the curves and make up your mind. A single power value is only good for advertising and cursory checks. We are talking about a "review," it is meant to be a critical appraisal.

...where the curves are in their full glory (except the one I would like) and the whole argument is the where to place the cursor!
That's odd people.

 

[Blumlein 88]

To be equally picky, I think you've forgotten that the FTC rules were instigated in 1974 and the only valid way of measuring THD included noise. There was no computerised FFT back then. Spectrum analysers were not even capable of high resolution measurements.

The standard measurement notched out the fundamental and measured the remainder. All THD meters worked that way.

It was the Audio Precision System One in about 1988/9 which re-defined the THD and N as separate and measurable metrics. Prior to that, we could measure residual and residual + distortion.

Well Audio had an early spectrum analyzer they were using for those spot measurements. This would have been in the 1980s, and yes I knew the FTC rule was from 1974. Audio used to show the screenshot or scope shot of the spectrum analyzer for their IM measures. Probably an HP or B&K and probably a 1024 FFT.

And I think if it had been possible to take out noise to see actual THD they would have approved, but cannot be sure.

 

[sarumbear]

...where the curves are in their full glory (except the one I would like) and the whole argument is the where to place the cursor!
That's odd people.

You are missing the point I'm afraid. Just scroll back and read this post to understand what is behind the argument.

 

[boXem]

I guess that what the best standard is to measure power can be discussed forever, but whatever that is, when you are comparing two amplifiers, like in post #1 March vs Boxem, the reviewer should use the same standard, whatever that is. It is evident the text of the review can be deceitful if you don't pay close attention to the graphs. It reads:

"4 Vrms input produces about 487 W @ 1% ( 487.3 W @ 1.027% )
....
You can compare this to another Purifi 1ET7040SA based amplifier yourself."

and immediately after:

View attachment 247483

when i read it the first time, i was "wow!"

but then if you look at both graphs in detail:

View attachment 247487 View attachment 247486
is this really a 500W amp vs a 300W amp?
I think the bare minimum here would be to at least add a note, and best to superimpose the graphs.

Thank you!
And that is the only thing that was requested: compare apple to apple.

 

[Blumlein 88]

OK, who fixed that standard, is there info on it? and who uses it? I did a quick browse of the big brands. Yamaha was quite thorough with many power figures, rated output power, effective max power, max power 10% THD, etc, this obviously give confidence you know where it's tested. but most other, Sony, Schiit, McIntosh, etc have no THD metric for max power, Should we then assume that they used that method? Me my first assumption was that if I don't see any information on where it's taken, I was probably not in the linear zone nor at "THD equivalent to 250 mW", I was assuming they would cherry pick a point that make the number bigger. It is good news if it is now standardised across the industry, and if it is indeed the case, That's also the number Amir should measure and publish, not best case THD, but I was not aware of that and I don't assume this when reading specs. Do you? I've seen 1% THD a lot, or 10% or nothing. If it is as you say the standard, then no info should just mean that. Does it?

That standard was the FTC of the USA and I think the IHF standard was either the same or very similar.

The FTC doesn't enforce it and is considering altering it a bit. They intend to change the max power number to .1% THD. It has been awhile since I looked at the FTC standard from 1974, but I think it said THD and IMD. The old standard also specified this testing was to be done after 60 minutes at 1/3 rated power and the new proposal is to change that to 1/8th rated power.

.1 % THD is about where most people can no longer hear distortion on test tones. With music it is more like 1% to 3% and much less clearly demarcated in testing done in psychoacoustics. I'd be okay with 1% for tube amps because distortion rises much more slowly in them. For all other types 1% is not a good point to use imo.

As for other testing like 5 watts Amir uses I think it is pretty well chosen. Anything between 250 mW and 5 watts is probably reasonable for most purposes.

 

[Sokel]

You are missing the point I'm afraid. Just scroll back and read this post to understand what is behind the argument.

I do get the argument,to measure both at around 100 SINAD,to compare (500 for one to 600-700 for the other).
The meaningful question to me is if (both) can perform,even distorted and to what extend.
My amp's company even states the allowed time for peak power and that power is even higher than Purifi's at 1%.
It's not like it's stopping.

 

[JasonWells]

Why do we need a single value to make a comparison? Look at the curves and make up your mind. A single power value is only good for advertising and cursory checks. We are talking about a "review," it is meant to be a critical appraisal.

Because that's not a "rating". what you arexsaying is that Amir should not state a "max power output"

 

[sarumbear]

Because that's not a "rating". what you arexsaying is that Amir should not state a "max power output"

A rating is a classification or ranking of someone or something based on a comparative assessment of their quality, standard, or performance. Max power does not qualify any of those. It is meaningless the way it is used by the industry.

 

[JasonWells]

Th

I guess that what the best standard is to measure power can be discussed forever, but whatever that is, when you are comparing two amplifiers, like in post #1 March vs Boxem, the reviewer should use the same standard, whatever that is. It is evident the text of the review can be deceitful if you don't pay close attention to the graphs. It reads:

"4 Vrms input produces about 487 W @ 1% ( 487.3 W @ 1.027% )
....
You can compare this to another Purifi 1ET7040SA based amplifier yourself."

and immediately after:

View attachment 247483

when i read it the first time, i was "wow!"

but then if you look at both graphs in detail:

View attachment 247487 View attachment 247486
is this really a 500W amp vs a 300W amp?
I think the bare minimum here would be to at least add a note, and best to superimpose the graphs.

The amps should be compared at the same thd levels. my view fwiw is 0.1% and 1% to cover amps that fall into the high levels.

Problem here is that Amirs testsxare not consistent and typically at thd levels that are well below audible thresholds. why rte power at 0.0018% thd? why not 0.0001%? what Amir is currently doing is totally arbitrary.

 

[JasonWells]

A rating is a classification or ranking of someone or something based on a comparative assessment of their quality, standard, or performance. Max power does not qualify any of those. It is meaningless the way it is used by the industry.

We are specifically talking about rating an amps power output. defining an absolute figure. amir does those on every test. it has to be subject to specific parameters to perform comparisons to other amps.

 

[tw99]

I love the way that March can cause an argument on here even when he's banned

 

[PeteL]

Why do we need a single value to make a comparison? Look at the curves and make up your mind. A single power value is only good for advertising and cursory checks. We are talking about a "review," it is meant to be a critical appraisal.

But the critic was about the value, so what are you debating on? You are totally right, we can look at the curve and make up our mind, this review has all the info we need, so what's to complain about? This review, or Amir's reviews, are not based on a single number.

 

[JasonWells]

I guess that what the best standard is to measure power can be discussed forever, but whatever that is, when you are comparing two amplifiers, like in post #1 March vs Boxem, the reviewer should use the same standard, whatever that is. It is evident the text of the review can be deceitful if you don't pay close attention to the graphs. It reads:

"4 Vrms input produces about 487 W @ 1% ( 487.3 W @ 1.027% )
....

He does explicitly state the conditions. He subsequently states the data and graphs should be compared for yourself.
I don't see how that is deceitful.

 

[JasonWells]

Thank you!
And that is the only thing that was requested: compare apple to apple.

I think your amp has been under rated on power in Amirs review.. Do you think 0.001% is audible clipping? why not 0..008% the next tested amp was rated at?

 

[sarumbear]

He does explicitly state the conditions. He subsequently states the data and graphs should be compared for yourself.
I don't see how that is deceitful.

You may not see it but many, who posted their views already, will.

 

[MCH]

He does explicitly state the conditions. He subsequently states the data and graphs should be compared for yourself.
I don't see how that is deceitful.

because Amirs values, pasted immediately after, are not measured in these conditions, and that very relevant difference is not indicated anywhere. Thats why i say that at least the reviewer should had added a note.

 

[JasonWells]

because Amirs values, pasted immediately after, are not measured in these conditions, and that very relevant difference is not indicated anywhere. Thats why i say that at least the reviewer should had added a note.

Thin blues initial statement was stand alone. it was not comparing the two amps. No need to post amirs numbers. he then said you can compare the data and posted the boxems graph for comparison.

 

[Sokel]

I can see the subjectivists having a party right now,who needs them when we can argue just fine about proper measurements.

 

[JasonWells]

I can see the subjectivists having a party right now,who needs them when we can argue just fine about proper measurements.

I think it should be borne in mind that Amir brought this up, but from whatvI xan see ge has no actual consistent methodology to instruct thin blue with.

 

[sarumbear]

Thin blues initial statement was stand alone. it was not comparing the two amps. No need to post amirs numbers. he then said you can compare the data and posted the boxems graph for comparison.

Their statement was not standalone. They were comparing the two amps! See below, copied from the first post.

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.
View attachment 247139
(https://www.audiosciencereview.com/.../boxem-arthur-4222-e1-amplifier-review.37930/)