Marchaudio P501 Mono Block Power Amplifier Review

[antcollinet]

crescendo doesn't mean loud, it just means a smooth transition to louder than before.

You just mean "consistently loud"

No, I just mean the loud parts of a track/song. Very often the end of a crescendo. Maybe there is a better word to use - I don't know it.

 

[MAB]

No, I just mean the loud parts of a track/song. Very often the end of a crescendo. Maybe there is a better word to use - I don't know it.

It's a great word, you used it well. I totally understood.

 

[xaxxon]

No, I just mean the loud parts of a track/song. Very often the end of a crescendo. Maybe there is a better word to use - I don't know it.

You can crescendo from ppp to pp - pianissimo is not loud.

You just mean loud.

 

[antcollinet]

To comfortably and cleanly listen to this from at my MLP I have to put it in the 85db region (as it has really low parts),so it's not only about transients (which it also has).
At my 84-85db sensitivity speakers at 3 meters I think I need a fair anount of power,not extreme but fair.And it's a single piano,I have far more "difficult" plays.

Is that 85dB average - or for the loud parts, or for the low parts. Or is it a number on the display

Difficult to be clear what we mean on this topic isn't it?

 

[Sokel]

No, I just mean the loud parts of a track/song. Very often the end of a crescendo. Maybe there is a better word to use - I don't know it.

You mean the "forte" or "fortissimo".
Crescendo is something we build gradually.

 

[antcollinet]

You just mean loud.

That is why I used the words "the loud parts of a track or song"

These do often occur at the end of a crescendo - presumably a pp to fff - or perhaps fffffffffffffff - crescendo has a more general, less music theory based definition also. Lets not get too far into arguing semantics - or musical notation where I would very quickly get lost

 

[amirm]

Wouldn’t that be exceptionally good to know if it does if that’s a worry??

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.

 

[PeteL]

Absolutely. But Amir is between a rock and a hard place. If he pushes the amplifiers to test their limits, some will fail/explode and then what does he do? Many are on loan from members and some are vintage, expensive or unrepairable.

But in my experience, well designed amplifiers are very hard to destroy. These Purifi and Hypex based amplifiers are virtually bulletproof and that means pushing them to their limits is not a problem. I'd be shorting them out, running them at full power for an hour etc. But that's me- I have a full repair lab...

Don't think it was from overdriving, but they are not bulletproof. I had a Hypex NC500 die on me after a year or so.

 

[restorer-john]

Don't think it was from overdriving, but they are not bulletproof. I had a Hypex NC500 die on me after a year or so.

I am not talking about reliability. That is a different issue and one not for this thread.

My comments are about high power testing. They have extensive protection systems to prevent destruction of the output MOSFETs and the ability to shutdown the power supply in mere milliseconds.

 

[amirm]

FYI the three amps I have killed in testing have all failed in the power supply section.

 

[JasonWells]

A lot of criticisms of how I measure amps is already addressed. Let me summarize:

1. My disagreement with OP was picking the highest/worst clipping point for one amp, and comparing it to my measurement where I pick the bottom of the hocky stick. You can argue that my measurement gives variable power rating for amps of different design. But you can't argue that picking the highest, worst clipping point for an amp is valid. That point can too vary depending on amp design and not at all correspond to 1% THD as it happens to do in this measurement. Had OP used a higher input level, it is possible that it could get worse than 1% THD as well.

Picking the knee of the curve gives the *design parameter* for the amp as far as power. It generates conservative watts rating as well but with variability due to lack of resolution of the graph at that point especially if the peak is very vertical. This is addressed in #2.

2. To deal with variability above, good while ago I added a new measurement that uses the same THD+N for the power measurements. It does this for both "continuous" and "peak" ratings:

3. I do run power vs frequency tests. Here it is:

This is superior to picking one power output and running the sweep vs frequency. You see full data for complete power sweep, albeit at discrete frequencies. Notice how picking the "knee" helps here to show the limited power at 20 Hz.

So you agree that your method gives variable max power readings for each amp. so you would agree that makes it difficult for people to compare one test to another. so you would agree that the headline "max power" you print on every graph can be misleading as it's not made under the same conditions each time.

So why don't you change your methods to determine power at a consistent level? if you feel it should be 0.001% thats fine. it doesn't really matter, although I would argue thats too low. Consistency however does matter.

Second point about the 1% level. it's not "the worst clipping point". that's just dramatising things for effect. it is simply 1% distortion level. its no less valid than the random points you choose that are far below any audible level of THD.

The research shows 1% is unlikely to be audible with music. you frequently test speakers that exceed this level, so don't ever egg the impact.

I don't even know what the "design parameters" of the amp means. it's simply a point where distortion starts to increase. The only relevant aspect of this is where on that knee the distortion starts to become audible. if you want to be conservative then research shows that with sine testing, the worst case scenario, it becomes audible around 0.1%. I don't see any justification for a lower point, but I would like to hear your view on that.

Also, If you object to 1% so much, why do you include the CEA busrt test which has its measurement point at 1%? you are contradicting yourself.

Basically I just don't understand your reluctance to choose a fixed distortion level, be it 0.001%, 0.01% or 0.1%. Variable levels on each test is the wrong thing to do. I don't know how you expect thin blue to conform to your methods when essentially there is no defined parameters for him to follow.

 

[amirm]

So you agree that your method gives variable max power readings for each amp. so you would agree that makes it difficult for people to compare one test to another. so you would agree that the headline "max power" you print on every graph can be misleading as it's not made under the same conditions each time.

Nope. No one should care about 5% variation in power that this method creates. A 350 watt power amp doesn't become 100 watts as you seem to be implying. It may be 350, 340 or 360. In my book, that is fine. Nothing is misleading about an approximate value. You are also shown the full graph so you can apply your own judgement if you want.

 

[amirm]

So why don't you change your methods to determine power at a consistent level?

Did you not bother to read my post which you quoted? I do exactly that:

The sweep response is doing more than determining power. These bar graphs however, are dedicated to that and use consistent criteria and have high precision.

 

[amirm]

Second point about the 1% level. it's not "the worst clipping point".

What? This is absolutely worst case for this amp:

The sweep ended at that point, registering the highest clipping point. Heck, it is even after the clipping occurred with a second kink in the graph. There is no way you can defend this practice as it is not consistent whatsoever. If you changed the input sweep level, it could stop at a different point. Ditto for driving it even harder. And different amps have different points where this graph stops. So this does not help your argument one bit unless you want inflated power ratings for amps to sell them.

 

[amirm]

I don't even know what the "design parameters" of the amp means.

Well then you need to learn about amplifier design. An amp either runs out of voltage or current. In either case, it can no longer produce more power and pushing it further just produces deformed waveform indicated by rapid rise in distortion. No one should operate an amplifier in that region if they want excellent fidelity.

 

[amirm]

The research shows 1% is unlikely to be audible with music. you frequently test speakers that exceed this level, so don't ever egg the impact.

There is no such "research." There are a couple of papers without use of proper trained listeners. Nature of said distortion also heavily impacts audibility so your generatlization is wrong on that front as well.

That aside, you can easily and trivially hear amplifier distortion over speaker distortion. Don't confuse the two. That is a lay argument with no merit. Go ahead and drive a tower speaker with a 5 watt amplifier that heavily and report back that you only hear speaker distortion.

Same is true in every headphone amp I test. I can easily drive low power amps to distortion before the headphone.

 

[Doodski]

@JasonWells have you ever used a oscilloscope. If we are measuring the clipping point with a oscilloscope it would be as soon as the rail voltage flattens out on a 1 kHz sine wave. The wattage figures doing it this way are probably even lower than you already dislike. The point I am making is that the standard(s) that @amirm is working to are pretty good.

 

[amirm]

Also, If you object to 1% so much, why do you include the CEA busrt test which has its measurement point at 1%? you are contradicting yourself.

For the forth time, OP compared 1% THD of one amp to knee of the curve in an amp I had measured with a fraction of the distortion. The problem is the comparison. Not the 1%. I am saying if you are going to put a point on the sweep graph, put it at the knee of the curve. Or put it somewhere else but then don't compare it to my measurement that use that logic.

 

[Holmz]

You will absolutely hear 20 Hz full clipping of the amplifier, assuming the speaker can reproduce it. We are not talking about small amounts of distortion here. I have tested a lot of underpowered amps and distortion in bass frequencies is quite audible when amp heavily clips.

I certainly agree with ^that.^

Is that 1% distortion actually clipping though?

I thought we were debating and pate rubbing about 0.1% versus 1%… and that clipping would likely be in the 10s of % or higher, pr maybe more like 50 to 100%.
(I admit I am bit lost.)

And sometimes the motor will actually have a nonlinear nature and the emitted field will start to look “compressed” and flattened, when the amp is not clipping. Especially in subs in small sealed boxes.

 

[amirm]

Basically I just don't understand your reluctance to choose a fixed distortion level, be it 0.001%, 0.01% or 0.1%.

Once more, this is done with the bar graph measurements. It is impossible to do with the sweep since you can't predict the distortion levels with fixed set of input levels. The only way to get there is to increase sweep resolution by 100 times, making the measurements take that much longer, and stress the amplifier that much. Even then you may not be able to get the same number in the exponential part of the curve.

The solution is the bar graph methodology where the analyzer hunts for specific fixed distortion level and when it gets there, it reports it. Not to ask for it in the sweep.