NC252MP (class D) vs. A250W4R (classAB) burst measurements into 4ohm//2.2uF load

[HarmonicTHD]

More facts, more measurements:

UcD180HG passed the test with 4.7ohm//(2.2uF+1.6uH+0.3ohm) load. Almost no difference with this complex load vs. resistor only. Also no additional noise spectrum problems.

View attachment 277236

View attachment 277237

So far:

Amplifier	class of operation	Result
Hypex NC252MP	class D	Failed
Hypex UcD180HG	class D	Passed
AIYIMA A07	class D LC filter behind feedback	Passed
A250W4R	class AB bipolar	Passed
PM-AB2	class AB MOSFET	Passed

Could you clarify to which “real” speakers these loads (R, I, C) correlate to?

It otherwise conveys the impression these are some random chosen values not having anything to do with real (commonly) used speakers.

Thx

 

[IAtaman]

@pma, can you please address the comment that all these behavior could be predicted by measuring the amps with resistive loads and calculating its output impedance.

Edit note : That, minus the overload behaviour outside of design range.

Another less technical question; if you are calling sorting by SINAD a cult, what do you think the appropriate label would be for the binary pass/ fail tests that you published on a website all kinds of people come for purchase advice on amps?

 

[SIY]

@pma, can you please address the comment that all these behavior could be predicted by measuring the amps with resistive loads and calculating its output impedance.

Careful- there's two sets of things discussed which are getting conflated. One is overload behavior when the amps are used outside of their design range. Source impedance will NOT predict that. The other was frequency response variations with reactive loads, and there, source impedance will absolutely predict the results.

 

[vicenzo_del_paris]

Once again, I might be very dumb, I don't understand the motivations for presenting the result of an exotic custom hardcore non representative load test as a failure for a given amplifier implementation when the test parameters are outside of its design specifications.
Sure other implementations would pass this test. Fine.
We could create any test that uses parameters outside of each target device design specifications and mark them as "failed". And so what? What value of it?
The argument given is "there might some existing speakers that matches this load test". Other responded, mostly not.
Then, one could argue, some speakers exhibiting a 0.1ohms load ar any frequency might exist (rhetorical statement). Shall we then create a discussion presenting all existing amplifier as "failures" with graph backing up such claim?
Once again, I don't care about the devices presented here in this topic neither their class or given implementation nor brand.
The whole stuff just seems odd and unfair, not saying biased. At least, this is my impression and thus lead me wonders about the motivations for it.
I am not an EE, just having basic /limited understanding of all the technical discussions / argument in this thread.

 

[Sokel]

Once again, I might be very dumb, I don't understand the motivations for presenting the result of an exotic custom hardcore non representative load test as a failure for a given amplifier implementation when the test parameters are outside of its design specifications.
Sure other implementations would pass this test. Fine.
We could create any test that uses parameters outside of each target device design specifications and mark them as "failed". And so what? What value of it?
The argument given is "there might some existing speakers that matches this load test". Other responded, mostly not.
Then, one could argue, some speakers exhibiting a 0.1ohms load ar any frequency might exist (rhetorical statement). Shall we then create a discussion presenting all existing amplifier as "failures" with graph backing up such claim?
Once again, I don't care about the devices presented here in this topic neither their class or given implementation nor brand.
The whole stuff just seems odd and unfair, not saying biased. At least, this is my impression and thus lead me wonders about the motivations for it.
I am not an EE, just having basic /limited understanding of all the technical discussions / argument in this thread.

I see it the other way around,that is fair to chase the best and the worst scenario in each device.

In real world conditions if possible,with normal (not 20cm) cables,unisolated,sitting in a rack with the usual spaghetti running everywhere.

That's user-useful,not ideal test-bench conditions.

 

[pma]

Once again, I might be very dumb, I don't understand the motivations for presenting the result of an exotic custom hardcore non representative load test as a failure for a given amplifier implementation when the test parameters are outside of its design specifications.
Sure other implementations would pass this test. Fine.
We could create any test that uses parameters outside of each target device design specifications and mark them as "failed". And so what? What value of it?
The argument given is "there might some existing speakers that matches this load test". Other responded, mostly not.
Then, one could argue, some speakers exhibiting a 0.1ohms load ar any frequency might exist (rhetorical statement). Shall we then create a discussion presenting all existing amplifier as "failures" with graph backing up such claim?
Once again, I don't care about the devices presented here in this topic neither their class or given implementation nor brand.
The whole stuff just seems odd and unfair, not saying biased. At least, this is my impression and thus lead me wonders about the motivations for it.
I am not an EE, just having basic /limited understanding of all the technical discussions / argument in this thread.

I am not interested in any kind of rhetorical excersises. I am bringing facts and measurements and I would not get involved in trolling debates that are based on opinions only. Anyone has an opinion. I have shown several times that the load is not unrealistic and I will not continue posting the same links round and round.

 

[boXem]

I see it the other way around,that is fair to chase the best and the worst scenario in each device.

In real world conditions if possible,with normal (not 20cm) cables,unisolated,sitting in a rack with the usual spaghetti running everywhere.

That's user-useful,not ideal test-bench conditions.

Did you calculate the length of speaker cable needed to reach 2 uF in // with the speaker load?

 

[boXem]

I am not interested in any kind of rhetorical excersises. I am bringing facts and measurements and I would not get involved in trolling debates that are based on opinions only. Anyone has an opinion. I have shown several times that the load is not unrealistic and I will not continue posting the same links round and round.

And several of us have demonstrated that your load is completely unrealistic. And you will continue to post the same thing, round and round. Wondering who is actually trolling here.

 

[Sokel]

Did you calculate the length of speaker cable needed to reach 2 uF in // with the speaker load?

Kilometers???
The comment was general,not only for cables and impossible speakers.

Edit:Immunity to the surrounding environment is a vitrue rarely tested,that's what the spaghetti condition.

 

[Deleted member 48726]

I am not interested in any kind of rhetorical excersises. I am bringing facts and measurements and I would not get involved in trolling debates that are based on opinions only. Anyone has an opinion. I have shown several times that the load is not unrealistic and I will not continue posting the same links round and round.

Is it this one?-->

NC252MP (class D) vs. A250W4R (classAB) burst measurements into 4ohm//2.2uF load

I am starting to wonder if you do not understand the advises on purpose. "the transformer has sufficient leakage inductance and series resistance" 0.3 Ohm is probably the resistance of the air core inductor. We don't know whether this is a realistic value, but it certainly is far below the...

audiosciencereview.com

 

[SIY]

However I doubt the audience is able to read impedance plots.

Condescension does not befit you. It may come as a great surprise, but you're not the only person who has ever done a measurement or designed a circuit.

 

[charlielaub]

Annoying and frustrating.

View attachment 277259

However I doubt the audience is able to read impedance plots.

Regarding this plot:

I will reiterate what I mentioned in an earlier post, that the designer of this loudspeaker should be shot. The impedance trends to a dead short above 20kHz. This is extremely negligent design practice. Besides this one speaker, what else you got? You know there have been tens of thousands of speakers designed with "normal" loads.... why focus on this one?

From the Stereophile review of this loudspeaker:

To investigate the answer to Dick's question, I measured the A-1's impedance magnitude at three settings of the Brilliance Control (BC) with DRA Labs' MLSSA system. With the BC set at Maximum (pot wide open), I obtained the curves in fig.1. Although the magnitude of the impedance is above 10 ohms from the upper bass to 2kHz, and well above 30 ohms in the bass, note the drop in the mid-treble and above. The cursor indicates a punishingly low 1.3 ohms at 20kHz with an equally punishing phase angle of –75.5°, dropping even further to just a small fraction of an ohm at ultrasonic frequencies. This measurement necessarily includes the resistance of the speaker cables DO was using (TARA Labs Rectangular Solid Core); as the margin of error in my measurement is probably around a fraction of ohm, it's quite possible that the A-1 presents amplifiers with a complete short circuit above the audio range.

 

[Deleted member 48726]

Annoying and frustrating.

View attachment 277259

However I doubt the audience is able to read impedance plots.

I may be daft but this does not really strike me as representation of an ordinary speaker. Not physical or electrical. Maybe I'm missing the point..

 

[Matias]

I guess pma found this "1 in a million" speaker that is representative of his load, and indeed it breaks the NCore amp. Congratulations.

Now is this representative of all the remaining speakers out there? Hell no!

So this thread is technically correct and those are facts, I do not question it. But just as his inaudible >20 kHz distortion measurements, or 250W burst into 20 kHz, these measurements here are just irrelevant as well. Correct, but irrelevant.

 

[AdamG]

However I doubt the audience is able to read impedance plots.

You earned a two week timeout for this one. Maybe that will give us enough time to study up on how to read and interpret an impedance plot.

On edit and to clarify: This is a “Temporary Thread reply ban”. Only restriction/limitation is relevant to this specific thread and/or Topic for a limited time.

 

[SIY]

I guess pma found this "1 in a million" speaker that is representative of his load, and indeed it breaks the NCore amp. Congratulations.

To be fair, Hypex is very clear in its specs about minimum design load. And this corner case is outside of spec. I could also drop line voltage to something below the rated minimum and show that the amplifier doesn't perform properly under those conditions, either.

 

[NTK]

I will reiterate what I mentioned in an earlier post, that the designer of this loudspeaker should be shot.

And this is how Sound Lab rated it.

Source:

Sound-Lab A-1 electrostatic loudspeaker Specifications | Stereophile.com

Sidebar 4: Specifications Description: Full-range, transformer-coupled, electrostatic loudspeaker. Frequency range: 28Hz to beyond 20kHz. Nominal impedance: 8 ohms. Sensitivity: equivalent to 88dB/1W/1m at 4m. Minimum amplifier power: 100W. Maximum music power: 450W. Bias power-supply input...

www.stereophile.com

 

[fpitas]

I can only imagine a lot of garden variety A/B amps get upset driving those things.

 

[boXem]

I guess pma found this "1 in a million" speaker that is representative of his load, and indeed it breaks the NCore amp. Congratulations.

I seriously doubt that this speaker presents a capacitive load to the amplifier above 50 kHz.

 

[fpitas]

I seriously doubt that this speaker presents a capacitive load to the amplifier above 50 kHz.

The phase angle is heading back to resistive. Maybe it flattens out at 0.2 ohms or something