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Marchaudio P501 Mono Block Power Amplifier Review

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JasonWells

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Yep.

That's distortion:

View attachment 247765


And that's what clipping looks like.
Ugly thing:

View attachment 247766
Bang on, and there is still an area in the transition between the two where the clipping still won't be audible, especially with music.again it's not about the graph shape, it's knee or clipping. it's about the distortion level and at what point it becomes audible. Rating an amps max power output at 0.001% thd doesn't make any sense.
 
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Sokel

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Bang on, and there is still an area in the transition between the two where the clipping still won't be audible, especially with music.again it's not about the graph shape, it's knee or clipping. it's about the distortion level and at what point it becomes audible.
What you see is a class A preamp which is suppose to clip softer.I expect to be a lot worst with a class D hard clipping.
(I really hope that my poor tweeters will never get to that torture)
 

pkane

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Bang on, and there is still an area in the transition between the two where the clipping still won't be audible, especially with music.again it's not about the graph shape, it's knee or clipping. it's about the distortion level and at what point it becomes audible. Rating an amps max power output at 0.001% thd doesn't make any sense.
The "knee" transition to a monotonically increasing distortion is an indication of where the amp has run out of clean power and is entering an increasingly non-linear stage. This point tells you a lot about the power capability of the amp, regardless of whether the distortion is audible or not right at that time. I’d rather know where that point is than the 1% THD, but that’s just me.

Since Amir provides both in his measurements, the knee transition point and the 1% THD, I don't see any reason to continue to argue.
 

sq225917

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Agreed, I want max power before clipping and Watts at a fixed value preferably 0.1% thd, but ultimately the graph shows all you need to know and we have that.

Seems like people are complaining that they can't read a graph.
 

JasonWells

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The "knee" transition to a monotonically increasing distortion is an indication of where the amp has run out of clean power and is entering an increasingly non-linear stage. This point tells you a lot about the power capability of the amp, regardless of whether the distortion is audible or not right at that time. I’d rather know where that point is than the 1% THD, but that’s just me.

Since Amir provides both in his measurements, the knee transition point and the 1% THD, I don't see any reason to continue to argue.
If you consider 0.001% thd non linear then fair enough. personally I don't. it's a long, long way below audibility. in any realistic sense Amir is under rating the power of the amps he measures. Not to mention the inconsist random levels he chooses.

People can always try the klippel distortion rest.

 

JasonWells

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Agreed, I want max power before clipping and Watts at a fixed value preferably 0.1% thd, but ultimately the graph shows all you need to know and we have that.

Seems like people are complaining that they can't read a graph.
Actually thin blue suggested people do just this and read the graph.. it was amir who complained it wasn't acceptable. it's also a bit of an assumption that the wider readership are technically aware enough. many just see headlines.
 
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Buckeye Amps

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Actually thin blue suggested people do just this. it was amir who complained it wasn't acceptable. it's also a bit of an assumption that the wider readership are technically aware enough. many just see headlines.
Actually Amir (along with boxem and others) were just pointing out that thin blue showing wattage at 1% next to/in comparison to Amir's review with wattage at the knee could be misleading to those who are just looking at headlines and are not technically aware enough, as you state.

But I guess if you're weekend is empty enough to argue for arguments sake, drawing that point out for x number of pages is possible.
 

PeteL

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Bang on, and there is still an area in the transition between the two where the clipping still won't be audible, especially with music.again it's not about the graph shape, it's knee or clipping. it's about the distortion level and at what point it becomes audible. Rating an amps max power output at 0.001% thd doesn't make any sense.
I think you guys are making this overly complicated. A sharp rise in distortion suggest that the amp is "clipping" whether if it's from voltage rail saturation or not enough current. It will look the same, clipping don't have to be an audibility metric, it doesn't have to mean huge distortion number, it don't even have to be visible on a oscilloscope. It's just a rapid rise in distortion, I think that the problem here is that Amir's wants to define the metric used and his rationale for picking a "knee", which indeed suggest clipping occurs. I assume that what he wanted to express is "the beginning of steepest slope in the power delivery graph means max power is obtained" but it have to be just assumption because he doesn't care to explain and answer the questions. If it's well defined, I don't mind that, like in this example there are 3 knees, Amir chose the steepest rise starting point as max power. OK, but it started rising before that. Softer clipping from below 200W at 4 ohms, harder clipping past 350 or so, they are all technically into "clipping" but defining where it starts to matter will always be arbitrary, or basing this on "audibility" will also always be just subject to any interpretation. We do need a number, I liked @restorer-john Idea on defining a operational spec at 250 mW and define this as when it can't match this THD spec max power is attained, I am also perfectly ok with. 0.01, 0.1, 1 numbers. As long as it's defined and it's clear. Let's not bring audibility into this, it's a power spec, it should define what power an amp can provide and you have to put a treshold somewhere and that treshold have to be clear. It's a power specification, not a fidelity specification. Me, for example. I don't hear the level distortion on this scope image. I don't know what THD percent it is. It's from a IEM wireless monitoring system. I don't know the level of distortion and don't hear it, but it's still a clipped signal. I have an ancient System one AP on a shelve but can't be bother to plug it in. It don't matter the number, it's clipped. It don't matter, trying to tie max power to an absolute "clipping point" will not work because as restorer john said, not everything will have the same slope, and it's ok to have peaks in that non linear zone, It appear that Amir don't want "any" clipping, but it will always be hard to define. The distinction should not be differentiate distortion to clipping, it is all about distortion,but one is a fidelity spec, one is a power behaviour spec, of couse the 2 are not to be confused clipping occurs when distortion rise, we are one derivative away.

1670166152084.png
clip.jpg
 

JasonWells

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Actually Amir (along with boxem and others) were just pointing out that thin blue showing wattage at 1% next to/in comparison to Amir's review with wattage at the knee could be misleading to those who are just looking at headlines and are not technically aware enough, as you state.

But I guess if you're weekend is empty enough to argue for arguments sake, drawing that point out for x number of pages is possible.
It's not for arguments sake. is this meant to be a scientific site? not sure why some appear to object to methods being scrutinised. I not sure i beleive you want your amps max power output being rated at 0.001% thd.
 

Rottmannash

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Oh no, that’s a misunderstanding. There is absolutely no reason for class A solid state amplifier to have softer clipping. Class A is only about idle current value. You would need to add soft clipping circuits to get “soft clipping”.
Totally off topic but what was that circuit NAD built into their old integrateds, "soft clipping"? My 3140 has it.
 

pkane

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If you consider 0.001% thd non linear then fair enough. personally I don't. it's a long, long way below audibility. in any realistic sense Amir is under rating the power of the amps he measures. Not to mention the inconsistency.

People can always try the klippel distortion rest.


Don’t know why you insist on audibility as being the only valid metric. I’ve done plenty of audibility testing on distortions and even created a tool for others to do this themselves. Whether or not certain THD level is audible depends on many things, including some that are unrelated to the amp. So I would rather avoid THD audibility debates and have an objective way to compare amps that tells me where the amp starts to run out of steam.
 

Buckeye Amps

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It's not for arguments sake. is this meant to be a scientific site? not sure why some appear to object to methods being scrutinised. I not sure i beleive you want your amps max power output being rated at 0.001% thd.
But he gives two "headlines" for power output during his reviews. He has stated this numerous times in his responses to you (and showed how he does it).

I for one definitely want my customers to know how much power they can expect at extremely low distortion levels and at a "max" output scenario. Which Amir does.

All that was asked originally is if someone is going to compare two amps, make sure the highlighted comparison is similar. Not that complicated.
 

JasonWells

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I think you guys are making this overly complicated. A sharp rise in distortion suggest that the amp is "clipping" whether if it's from voltage rail saturation or not enough current. It will look the same, clipping don't have to be an audibility metric, it doesn't have to mean huge distortion number, it don't even have to be visible on a oscilloscope. It's just a rapid rise in distortion, I think that the problem here is that Amir's wants to define the metric used and his rationale for picking a "knee", which indeed suggest clipping occurs. I assume that what he wanted to express is "the beginning of steepest slope in the power delivery graph means max power is obtained" but it have to be just assumption because he doesn't care to explain and answer the questions. If it's well defined, I don't mind that, like in this example there are 3 knees, Amir chose the steepest rise starting point as max power. OK, but it started rising before that. Softer clipping from below 200W at 4 ohms, harder clipping past 350 or so, they are all technically into "clipping" but defining where it starts to matter will always be arbitrary, or basing this on "audibility" will also always be just subject to any interpretation. We do need a number, I liked @restorer-john Idea on defining a operational spec at 250 mW and define this as when it can't match this THD spec max power is attained, I am also perfectly ok with. 0.01, 0.1, 1 numbers. As long as it's defined and it's clear. Let's not bring audibility into this, it's a power spec, it should define what power an amp can provide and you have to put a treshold somewhere and that treshold have to be clear. It's a power specification, not a fidelity specification. Me, for example. I don't hear the level distortion on this scope image. I don't know what THD percent it is. It's from a IEM wireless monitoring system. I don't know the level of distortion and don't hear it, but it's still a clipped signal. I have an ancient System one AP on a shelve but can't be bother to plug it in. It don't matter the number, it's clipped. It don't matter, trying to tie max power to an absolute "clipping point" will not work because as restorer john said, not everything will have the same slope, and it's ok to have peaks in that non linear zone, It appear that Amir don't want "any" clipping, but it will always be hard to define. The distinction should not be differentiate distortion to clipping, it is all about distortion,but one is a fidelity spec, one is a power behaviour spec, of couse the 2 are not to be confused clipping occurs when distortion rise, we are one derivative away.

View attachment 247780View attachment 247786

So if you want to ignore audibility, then clipping is just a technical statement. a technical measurement for measurements sake. you can see why the hardened subjectivist take issue with objectivists. it's like the sinad wars. it has no meaning. It doesn't matter one bit if it's 117dB or 120dB.
So you say Amir doesnt want any clipping. so why not zero distortion. why stop at 0.001% why not 0.0001%.

You need to have a level that's related to thecreal world.

Johns 250mW level doesn't make any sense. As I pointed out earlier 250mW on a typical 85dB sensitivity speakerxat 3m listening distance might only be 72dB spl. That's quiet. again why choose that level? Amirs 5 watt rating is a more realistic listening level.
 

JasonWells

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Don’t know why you insist on audibility as being the only valid metric. I’ve done plenty of audibility testing on distortions and even created a tool for others to do this themselves. Whether or not certain THD level is audible depends on many things, including some that are unrelated to the amp. So I would rather avoid THD audibility debates and have an objective way to compare amps that tells me where the amp starts to run out of steam.
I'm not. I just don't see any valid justification for the random extremely low thd levels amir chooses. See my points above about the relevance of measurements.
 

tonycollinet

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It's not for arguments sake. is this meant to be a scientific site? not sure why some appear to object to methods being scrutinised. I not sure i beleive you want your amps max power output being rated at 0.001% thd.

You keep making the same point over and over. You've been anwered multiple times. You keep going on and on, knowing you're not going to get a different answer. You seem unable to agree to disagree. No longer interested - blocked.
 

JasonWells

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But he gives two "headlines" for power output during his reviews. He has stated this numerous times in his responses to you (and showed how he does it).

I for one definitely want my customers to know how much power they can expect at extremely low distortion levels and at a "max" output scenario. Which Amir does.

All that was asked originally is if someone is going to compare two amps, make sure the highlighted comparison is similar. Not that complicated.
Yes I know how he does it and its wrong. He also says 1% is too high sonI don't know why he is posting the 1% burst test.

OK, you and boxem make similar amps. what if Amir measures yours at 0.001% and boxems at 0.01%. yours will look inferior WRT power. that's what he is doing. I would have thought you would want a level playing field.

These are the levels for the most recent tests.

-41.6dB. 0.83%
-81.8dB 0.008%
-61.4dB 0.085%
-98.9dB 0.001%
-87.8dB 0.004%
 
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PeteL

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But he gives two "headlines" for power output during his reviews. He has stated this numerous times in his responses to you (and showed how he does it).

I for one definitely want my customers to know how much power they can expect at extremely low distortion levels and at a "max" output scenario. Which Amir does.

All that was asked originally is if someone is going to compare two amps, make sure the highlighted comparison is similar. Not that complicated.
Yes and no. I personally also like Amir think that those two graphs should not be compared, if so it should have been clearly stated "You can compare the two graph but pay attention to not compare the max power spec, the cursor is not at the same place". But that's not "All that was asked" What was said was that putting the cursor at 1% was "wrong". even tough it was meant to be also compared to Purifi spec sheet. If it's about the comparison to Boxem I fully agree with you.
 

PeteL

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So if you want to ignore audibility, then clipping is just a technical statement. a technical measurement for measurements sake. you can see why the hardened subjectivist take issue with objectivists. it's like the sinad wars. it has no meaning. It doesn't matter one bit if it's 117dB or 120dB.
So you say Amir doesnt want any clipping. so why not zero distortion. why stop at 0.001% why not 0.0001%.

You need to have a level that's related to thecreal world.

Johns 250mW level doesn't make any sense. As I pointed out earlier 250mW on a typical 85dB sensitivity speakerxat 3m listening distance might only be 72dB spl. That's quiet. again why choose that level? Amirs 5 watt rating is a more realistic listening level.
I'll let you guys argue on what the number should be.
 

PierreV

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Regardless of the arbitrary graphing, anyone who believes for even an instant that the same Hypex/Purifi modules with identical or similar power supply could deliver wildly different results should go back to their homework. Yes, there are clear indications that some integrators 1) do a better job in routing cables, which can get them a few more dBs of SNR 2) have better QC but this isn't what it is about.

As far as the semi-arbitrary max power levels Amir provides are concerned, while they don't necessarily allow for strict numerical comparison, we also all should know that this is where Amir estimates the amp starts to break down. Given that different amp architectures break down in different ways, I don't see how you can avoid some fuzziness.
 
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