Marchaudio P501 Mono Block Power Amplifier Review

[JasonWells]

@JasonWells what is your position on this % figure. Do you have a opinion. What is your back ground on the matter?

OK, let's ask the question why are we trying to determine an amps max power output. two major reasons I can think of, you might think of more. to get an idea how loud it might play, and secondly for comparison to other amps. you may be making a purchasing decision.

We have to assume that the basis of this rating is to be without overtly noticeable distortion. THD is a pretty poor metric of audible quality, but it's what we are using.

So obvious question is where do you define "noticeable". it has ZERO to do with the shape of the curve or its knee. it's a thd level you need to define.

Harmonic distortion is actually quite difficult to hear in music. it's audibility varies with frequency, the ear ERB, masking and so on. So it's pretty difficult, maybe impossible to obtain a definitive figure. however with simple tones you can obtain some reliable numbers. It also turns out you are much more sensitive to hearing distortion with sines because you don't have all the masking effects of broadband music.

The research shows THD figures around 0.1% are the threshold, but this is still dependant on frequency etc etc. Hence my view 0.1% is a sensible fighure, it has justifiable merit. it should bexbelow any audible threshold with music and is conservative in this respect. you can test this really easily yourself, no need to take my word for it.

Choosing numbers at 0.001% level makes no sense to me, it way below audibility and has no justification in the context of the purpose of the test. especially when driving speakers that will have 100 to a 1000x more thd.

my second bugbear is that the levels Amir measures are random. they change on every test. no consistency, no ability to compare. his headline numbers on the graphs of max power are under rated and misleading.

1% is high, too high imo, but still probably not overtly noticeable with a lot of music. so massive complaints about 1% are unjustified imo. at least amps are being compared at the same level. you also have the issue that some amps can't acheive low levels of thd. amir just rated one at 0.85%.

So imo two thd power levels should be presented, one at 0.1% and the second at 1%.

 

[Doodski]

So imo two thd power levels should be presented, one at 0.1% and the second at 1%.

That certainly cuts the wheat from the chaff but nobody gets to see why because your tests are too easy for the gear. What about the gear that tests very well and is class leading everything?

 

[restorer-john]

What about the gear that tests very well and is class leading everything?

But can you see the irony here? Purifi claim to be class leading etc, etc and yet they specify their power output advertising numbers at 1% THD...

Can't have it both ways.

 

[JasonWells]

That certainly cuts the wheat from the chaff but nobody gets to see why because your tests are too easy for the gear. What about the gear that tests very well and is class leading everything?

You still publish the full graph. in any case you are not testing for the lowest distortion point, your testing for "power rating ". A max power output for a given, just below audible distortion level. the good amps will just show higher power output at the measured Max point.

 

[JasonWells]

But can you see the irony here? Purifi claim to be class leading etc, etc and yet they specify their power output advertising numbers at 1% THD...

Can't have it both ways.

Wrong.

They publish the most comprehensive test data.

https://vtvamplifier.com/wp-content/uploads/2022/03/1ET7040SA.pdf

 

[Doodski]

@JasonWells you want to change the entire trajectory of the HiFi and AV business? Why?

 

[restorer-john]

Wrong.

They publish the most comprehensive test data.

Read the first headline power output number.

We've been discussing this for a long time. Years in fact. Plenty of threads here you could research. Harold Leak proposed 0.1% THD as the figure, in 1951 and released a range of amplifiers called, wait for it, the Point One.

Now, for the record, I think 0.1% is a good number. 0.08% is easy to see the onset of waveform clipping on a scope, which is 12.5 times less than 1%.

 

[JasonWells]

Read the first headline power output number.

We've been discussing this for a long time. Years in fact. Plenty of threads here you could research.

Now, for the record, I think 0.1% is a good number. 0.08% is easy to see the onset of waveform clipping on a scope, which is 12.5 times less than 1%.

Nothing wrong with it. it specifies the test condition. it then shows you the full graph and the data goes on to specify power at different levels of thd. I don't see what your point is.

If it's been discussed many times before, why does Amir continue to do the wrong thing?

Isn't the point about audibility, not a specific level, not a knee shape. can you hear 1% in music?

 

[JasonWells]

@JasonWells you want to change the entire trajectory of the HiFi and AV business? Why?

I'm not sure what you are referring to or understand your comment. my comments have specifically addressed the testing performed in this thread and Amirs criticisms of it. it's just a natural progression that Amirs methods are examined. Amir wants thin blue to follow his example, but how can thin blue do that if Amirs methods have no consistent defined or justifiable parameters?

 

[PeteL]

OK, let's ask the question why are we trying to determine an amps max power output. two major reasons I can think of, you might think of more. to get an idea how loud it might play, and secondly for comparison to other amps. you may be making a purchasing decision.

We have to assume that the basis of this rating is to be without overtly noticeable distortion. THD is a pretty poor metric of audible quality, but it's what we are using.

So obvious question is where do you define "noticeable". it has ZERO to do with the shape of the curve or its knee. it's a thd level you need to define.

Harmonic distortion is actually quite difficult to hear in music. it's audibility varies with frequency, the ear ERB, masking and so on. So it's pretty difficult, maybe impossible to obtain a definitive figure. however with simple tones you can obtain some reliable numbers. It also turns out you are much more sensitive to hearing distortion with sines because you don't have all the masking effects of broadband music.

The research shows THD figures around 0.1% are the threshold, but this is still dependant on frequency etc etc. Hence my view 0.1% is a sensible fighure, it has justifiable merit. it should bexbelow any audible threshold with music and is conservative in this respect. you can test this really easily yourself, no need to take my word for it.

Choosing numbers at 0.001% level makes no sense to me, it way below audibility and has no justification in the context of the purpose of the test. especially when driving speakers that will have 100 to a 1000x more thd.

my second bugbear is that the levels Amir measures are random. they change on every test. no consistency, no ability to compare. his headline numbers on the graphs of max power are under rated and misleading.

1% is high, too high imo, but still probably not overtly noticeable with a lot of music. so massive complaints about 1% are unjustified imo. at least amps are being compared at the same level. you also have the issue that some amps can't acheive low levels of thd. amir just rated one at 0.85%.

So imo two thd power levels should be presented, one at 0.1% and the second at 1%.

Audibility is not a concern. It’s a max power spec, not an operating spec. even if listening to music with 1% distortion can be detected, If you stay within power spec at all time, Ans that’s. the idea, you will not be listening at 1% distortion,, only the extreme peaks will be distorted by that much, we are talking milisecond transients or extreme Explosive basses that will suffer from generating low level harmonics. nothing deceptive there, the amp can do this. I don’t know why would max power would be synonym with clipping point, if it can provide more power it hasn’t reach max power. I don’t see what’s wrong with 1% if it’s clearly indicated.

 

[JasonWells]

Audibility is not a concern. It’s a max power spec, not an operating spec. even if listening to music with 1% distortion can be detected, If you stay within power spec at all time, Ans that’s. the idea, you will not be listening at 1% distortion,, only the extreme peaks will be distorted by that much, we are talking milisecond transients or extreme Explosive basses that will suffer from generating low level harmonics. nothing deceptive there, the amp can do this. I don’t know why would max power would be synonym with clipping point, if it can provide more power it hasn’t reach max power. I don’t see what’s wrong with 1% if it’s clearly indicated.

You do bring up an excellent point. in the real world you will never run any amp anywhere near its rms max power. sorry I know it's not rms for the pedantics amongst you . Music has a low rms signal level compared to the peak. so really the burst power is the most relevant figure.

 

[amirm]

I'm not sure what you are referring to or understand your comment. my comments have specifically addressed the testing performed in this thread and Amirs criticisms of it. it's just a natural progression that Amirs methods are examined. Amir wants thin blue to follow his example, but how can thin blue do that if Amirs methods have no consistent defined or justifiable parameters?

Once more... it doesn't matter to me what Thin Blue does. What he shouldn't do is measure power on the sweep with the cursor at the last clipping point, and compare it to my measurement of an amp where I put the clipping point at the knee.

The amp he measures has THD of 1% at his cursor, whereas mine is at 0.001% or 100 times less. Clearly I could have moved the cursor to the right and put it at the top of graph to show "more power." But as I have repeatedly explained, that is not proper.

As to "examining" my methods, all I am reading is that you don't understand them or my explanation of the same. You keep demanding to know power at one distortion level. I showed you that in a different measurement. The sweep method above CAN NOT show you that. It is by accident that OP's measurement landed on 1%. It could end any where it wants.

 

[restorer-john]

so really the burst power is the most relevant figure.

You're not fooling anyone, 'Jason'.

 

[amirm]

You do bring up an excellent point. in the real world you will never run any amp anywhere near its rms max power. sorry I know it's not rms for the pedantics amongst you . Music has a low rms signal level compared to the peak. so really the burst power is the most relevant figure.

No it isn't because you can't say one test with a fixed peak resembles all music and content. It is another value so I post it, mostly to show if there is headroom.

 

[amirm]

You're not fooling anyone, 'Jason'.

He always shows up, doesn't he?

 

[amirm]

Harmonic distortion is actually quite difficult to hear in music. it's audibility varies with frequency, the ear ERB, masking and so on. So it's pretty difficult, maybe impossible to obtain a definitive figure. however with simple tones you can obtain some reliable numbers. It also turns out you are much more sensitive to hearing distortion with sines because you don't have all the masking effects of broadband music.

Given this, I assume you agree that no one should be in the market to buy March Audio amp. Find a much cheaper, high distortion one instead. Tons of commercial class D amps do that job for much less money. I am thinking Crown, Behringer, etc. Agree?

 

[amirm]

OK, are you up for some abx testing with sine waves? let's see what distortion you can hear. we can even try some of the levels you have defined max power at in recent tests, 0.001%, 0.085% etc.

You made the claim of inaudibility, I did not. So you need to provide proof. For my part, I can do one better with published ABX test with real music:

Double Blind tests *did* show amplifiers to sound different

In many online debates, position taken by some that when amplifiers are used that have flat frequency response and low distortion that no double blind tests have shown them to sound different. Well, I managed to dig up a 32 year old test that says otherwise. What is fascinating is that one of...

www.audiosciencereview.com

This small incursion into clipping region caused this result:

This is why you want to avoid going beyond the knee of the distortion sweep test.

 

[xaxxon]

Not for the owner that sent it. And me trying to make him whole again!

You don't push your amp the way that sweep does.

I speak from experience having blown up amps during previous incarnations of these tests.

Can you make a video about the dangers associated with amp testing? I’d be super interested.

I’d be willing to provide one of my ahb2 amps for you to abuse. They seem pretty rock solid.

If you want I can provide a carver 275 for you to destroy. I don’t use it anymore and they won’t take it back.

 

[PeteL]

You made the claim of inaudibility, I did not. So you need to provide proof. For my part, I can do one better with published ABX test with real music:

Double Blind tests *did* show amplifiers to sound different

In many online debates, position taken by some that when amplifiers are used that have flat frequency response and low distortion that no double blind tests have shown them to sound different. Well, I managed to dig up a 32 year old test that says otherwise. What is fascinating is that one of...

www.audiosciencereview.com

This small incursion into clipping region caused this result:

This is why you want to avoid going beyond the knee of the distortion sweep test.

I have no doubts amps can sound different and this confirms it. I am however curious of their methodology to confirm with a 80s scope with music content, that all these amps clipped 1% of the time. I don’t dismiss the finding, I just don’t see it, there was only analog scope back then? and assessing a « time » metric? unless the « about » is very very very approximate, I would not know how to….

 

[Holmz]

I’d be willing to provide one of my ahb2 amps for you to abuse. They seem pretty rock solid.

How does the same person own a Benchmark AND a Carver?
(That seems like it would be a difficult combo of amps to own, and a rarity to find in the same abode.)

If you want I can provide a carver 275 for you to destroy. I don’t use it anymore and they won’t take it back.

Is OSHA no longer a thing in the US?