• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Marchaudio P501 Mono Block Power Amplifier Review

Status
Not open for further replies.

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
앰프의 최대 출력을 판단하기 위해 어떤 기준을 사용하는지 설명해 주시겠습니까?
그 기준으로도 포스팅할 수 있을 것 같아요!

View attachment 247427
THD+N 비율 0.00018%

View attachment 247428
THD+N 비율 0.05077%

View attachment 247429
THD+N 비율 0.01691%

View attachment 247433
THD+N 비율 0.00024%

View attachment 247435
THD+N 비율 0.02086%

View attachment 247436
THD+N 비율 0.03586%

View attachment 247437
THD+N 비율 0.00089%

View attachment 247438THD+N 비율 0.00114%

-----
다른 회원의 편의를 위한 환산표
1%를 dB로 환산
20*로그(1/100)= -40dB

0.1%를 dB로 변환
20*로그(0.1/100)= -60dB

0.01%를 dB로 변환
20*로그(0.01/100)= -80dB

0.001%를 dB로 변환
20*로그(0.001/100)= -100dB)
----


View attachment 247440
일관성 있고 1 % 포인트가 합리적이라고 생각했습니다. 마케팅 메시지를 돕기 위한 것이 아닙니다. 나 자신 도 적절한 필터와 부하를 사용한
첫 번째 검토에서 1% 가치를 주장 했습니다. 양해 바랍니다.

당신은 오디오 사회의 진정한 후원자입니다.
그래서 내 목표는 당신처럼 사람들에게 정보를 제공하는 것입니다!
Im unclear of what you are trying to show with these graphs. can you explain?
 

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
2,732
Likes
2,928
The actual standard (which is still in force) for advertised power ratings covers the range from 250mW to rated power across a specified bandwidth with a single distortion metric which is never exceeded at any point across the rated frequency range. It is not a cherry-picked best case THD (at the bottom of the curve) number to plaster all over your products. Or is it one that goes so far up the distortion curve that, just before the unit shuts down, you pick a power number. That, is deceptive. Purifi and Hypex (and some others for sure) just pick inflated headline best case figures because they think most high fidelity aficionados are ignorant. News flash! They aren't.

The rating in place, rules out picking 'inflexion' points, or 'knees' in the curve, because most of the time, the THD+N at 250mW is already way above the bottom of the curve where dubious manufacturers like to quote their numbers. With power amps, I'd draw a line from 250mW horizontally until it hit the upper power curve and you'd be on the money every time. The class Ds clip hard and fast- straight up. Plenty of other amps, are much slower and 'ease' into clipping. i.e. the shape of the curve is way less vertical.

This high powered March amplifier clearly performs very well, and has more than enough power for any domestic situation, but its 1kHz THD+N at 250mW means it would get an approximate rated 0.0025%THD+N from 250mW to 370/[email protected] That would deteriorate significantly for a 20Hz-20kHz rating. Those numbers are not earth shatteringly excellent or game changing, but they are good.

It is not a 1kW high fidelity amplifier. It is well into complete non-linearity at or near that power output. That is the point Amir was making and it stands.
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?
 

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
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?
It's not an international technical standard. it's was instigated by the ftc for advertising "fairness" in the US only. nothing else. it's an outdated blunt instrument and IIRC it's being considered to get rid of/updated. No one pays any attention to it and it's not enforced.
 

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
This discussion happened on ASR several years ago. In front of the lack of consensus, @amirm decided to measure the power at the onset of audible clipping, like it or not. Since then all amplifiers have been measured like that. Why is this subject coming back?
@boXem | audio What would you define as audible clipping? Looking at @thin bLue post above Amir has measured max power at very low distortion levels. All very much below audible in my opinion. what do you think?boxem
Out of the amps shown the thd+n varies from 0.00018% to 0.05%. is any of that thd audible?
 
Last edited:

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
2,732
Likes
2,928
This discussion happened on ASR several years ago. In front of the lack of consensus, @amirm decided to measure the power at the onset of audible clipping, like it or not. Since then all amplifiers have been measured like that. Why is this subject coming back?
I was talking about the whole industry, Not ASR specifically. Amir is obviously allowed to not publish third party reviews that don't respect ASR methods, I have no problem with that, but I don't think this review, as far as I know, was written for ASR specifically and it is clear from the sequencing of measurments and spec datas that the goal of the reviewer was to compare the achieved measured performance to the Purifi specifications, It make sense if that's the goal it should use the same metric, don't it? The subject is coming back because Amir pointed it out as wrong. I think he should just say "keep in mind that your figure cannot be directly compared to mine" Instead of. "The way you are measuring is wrong"
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319
As you already know, 1% is one of the industrial standard. so most of Amp commercials are at 1%.
(Like https://www.tpdz.net/productinfo/821195.html)
You seem to have failed to understood the reason of ASR's existence. ASR is trying to highlight the bad behaviour of the audio industry and shame them when they are caught doing it.

Maybe such tests should not be promoted to the home page. The last thing ASR needs is to amplify someone arguing like an industry representative.
 

pma

Major Contributor
Joined
Feb 23, 2019
Messages
3,574
Likes
7,587
Location
Prague
This discussion happened on ASR several years ago. In front of the lack of consensus, @amirm decided to measure the power at the onset of audible clipping, like it or not. Since then all amplifiers have been measured like that. Why is this subject coming back?
Because in many cases, like typical tube amplifiers, such method is a nonsense. Is this a 1W amplifier???


1670074654772.jpeg
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319
I think that was not fair.
Thin blue always enthusiastically follows suggestions and a measurement against company's measurement is not wrong,on the contrary,could be reveling some times.
It's not like is hiding the rest.
For me it was. There is no place in my book when a reviewer justifies their inflated test results because "1% is one of the industrial standard. so most of Amp commercials are at 1%."

Why would anyone care about an industry standard when it is four orders of magnitude higher than some amplifiers sold even in the last century?
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
I think that was not fair.
Thin blue always enthusiastically follows suggestions and a measurement against company's measurement is not wrong,on the contrary,could be reveling some times.
It's not like is hiding the rest.
I agree I think @thin bLue is trying to follow Amirs example. However what distortion level should he rate a power amplifier at?

Let's look at Amirs most recent tests.

Carver Raven Monoblock 350 watts Amplifier Power into 4 ohm Measurements.png

-41.6dB. 0.83%


JBL SDR 4K HDMI Hom Theater Audio Video Receiver Amplifier CD Input Power 4 ohm Measurements.png

-81.8dB. 0.008%

JBL SA600 Stereo Amplifier Vintage integrated Power 4 ohm measurements.png

-61.4dB. 0.085%

BoXem Arthur 4222E1 Monoblock Amplifier Power into 4 ohm Measurement.png

-98.9dB. 0.001%

Denon AVR-3800H AVR Aanalog Input Amplifier Power 4 Measurements.png

-87.2dB. 0.004%

The powe rating is taken at thd levels ranging from 0.85% to 0.001%.

Im not sure what thin blue is meant to draw from this and how he is meant to determine at what point he should rate an amps power to be consistent with ASR.
 

pma

Major Contributor
Joined
Feb 23, 2019
Messages
3,574
Likes
7,587
Location
Prague
No, but it is a very high-distortion audio amplifier.
…. and this distortion in isolation would be in almost any case inaudible. FR modulation due to higher output impedance might be audible. Harmonic low order distortion as shown will be inaudible on music signal. This was shown many times. So again - rated power cannot be automatically measured in the knee of the THD+N curve.
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319
…. and this distortion in isolation would be in almost any case inaudible. FR modulation due to higher output impedance might be audible. Harmonic low order distortion as shown will be inaudible on music signal. This was shown many times. So again - rated power cannot be automatically measured in the knee of the THD+N curve.
If you say distortion at 1% is acceptable then the only option is to agree to disagree.
 

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
For me it was. There is no place in my book when a reviewer justifies their inflated test results because "1% is one of the industrial standard. so most of Amp commercials are at 1%."

Why would anyone care about an industry standard when it is four orders of magnitude higher than some amplifiers sold even in the last century?
1% isn't the point. the point is that you need a consistent level to perform comparisons. it could be 1% or 0.1%. what it must not be is different on every test.
 

JasonWells

Member
Joined
Dec 3, 2022
Messages
76
Likes
32
If you say distortion at 1% is acceptable then the only option is to agree to disagree.
So in your opinion, what level is audible, and what level should the power be rated at?
Bear in mind that speakers easily hit 1% thd
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
5,873
Likes
5,319
the point is that you need a consistent level to perform comparisons.
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.
 

MarcosCh

Major Contributor
Joined
Apr 10, 2021
Messages
1,689
Likes
1,334
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:

1670075878875.png


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

but then if you look at both graphs in detail:

1670076102825.png
1670075980151.png

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.
 
Status
Not open for further replies.
Top Bottom