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Power amplifier tests with respect to FTC: 16 CFR Part 432 (July 5, 2024) requirements on output power claims

The 5 minute test should be done at rated power which is continuous average power which is clearly stated on the NC252MP data sheet as 50 watts not 250W / 4 ohm that is Max output.
50W is stated, in the datasheet, as a continuous power. Other power definitions in the datasheet remain quite unclear.

§ 432.4 Optional disclosures.
Other operating characteristics and technical specifications not required in § 432.2 of this part may be disclosed:
Provided:
(a) That any other power output is rated by the manufacturer, is expressed in minimum watts per channel, and
such power output representation(s) complies with the provisions of § 432.2 of this part; except that if a
peak or other instantaneous power rating, such as music power or peak power, is represented under this
section, the maximum percentage of total harmonic distortion (see § 432.2(d) of this part) may be
disclosed only at such rated output: And provided further,

(b) That all disclosures or representations made under this section are less conspicuously, and prominently
made than the disclosures required in § 432.2 of this part; and
(c) The rating and testing methods or standards used in determining such representations are disclosed, and
well known and generally recognized by the industry at the time the representations or disclosures are
made, are neither intended nor likely to deceive or confuse the consumers and are not otherwise likely to
frustrate the purpose of this part.

So may I ask you, according to your opinion, Hypex NC252MP rated power is 2 x 50W/4ohm ? If this is your suggestion, then I have no objections and confirm that the amp passed the test easily.
....
But, what would be this, then?
1733256216977.png

A "hausnummer"? It should not be
intended nor likely to deceive or confuse the consumers
?
 
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Also,the "music" argument (and the reduced power needs) is not as solid as we think and depends on the application.
At this thread for example tests were made with LFE channel material of Interstellar's Wormhole Scene which proved to be specially demanding.
They were not for 5 min though,but for about 1 minute,but at least way more than the usual few ms we see around.

(an icepower module found faulty and a Hypex NC502MP died during the tests,@StigErik can tell us more about it)
My Hypex NC502MP sitting in a FusionAmp 502 did well with one channel driven down to 3 ohms. It quickly went into protection and never worked again in BTL mode at 8 ohm load…
 
I agree with the need for honest measurements. I'm glad for the new FTC rules, and definitely appreciate your time and effort in testing.

But I also think that in all fairness to some of these amps, if their ratings were created prior to the FTC rules that the reports should state that very clearly. In other words, you're expecting them to pass a test that they never claimed they would pass. As a consumer I appreciate knowing that the amp doesn't meet the expectations implied by the FTC, but it's unfair to the engineers who created these products to say they are failing when they never claimed that they would pass.
The reality is that it’s uncertain what standards or guidelines many are relying on to define their ratings. In the past, reputable manufacturers consistently disclosed their specifications in alignment with various established norms, ensuring clarity and consistency for consumers.

There’s no reason to interpret this as a deliberate effort to undermine the enjoyment of music or lessen the pride of owning equipment. It’s fundamentally about transparency. For serious brands, adhering to recognized standards and openly sharing continuous power ratings has always been the accepted practice.

The resistance to this approach is genuinely puzzling.

1994:
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1988:
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1982:
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1978:
1733289229640.png
 
Internet forum posting is available to anyone. Anyone from laymen audience feels free to put his comments, regardless knowledge - we can see the results. Unfortunately, same approach reflects in behaviour of some manufacturers as well.
 
This is my take on approach of the amplifier modules producers - Hypex NC252MP as an example, as it has been tested and discussed.

They publish some buck-passing data in the datasheet, like "Max Output Power 1KHz, THD=1%, All channels driven. Per channel PR, 4Ω - - 250 Wrms 1)", where 1) is: "
Note 1: The stimulus signal is a continuous 1 kHz sine wave. The true rms output voltage is measured across a load resistor. Max output power is time limited due to thermal properties"
Then another definition like: "Continuous Output Power Per channel, 25°C ambient temperature. PR,cont - 50 - Wrms 2)" where 2) is: Note 2: Typically, this is 1/5 of the peak output power. Apply sufficient cooling.

Maximum power conditions are undefined, the only defined is continuous power 50 Wrms with note apply sufficient cooling. So, the whole responsibility is transferred to the OEM assemblers and sellers to define the rated power. BTW, that "Wrms" is a nonsense. Power is power and the unit is [W]. Power is rms value by its definition.
But, Hypex also published the notes on thermal design

and as an example they show:
1733297525160.png


1733297611362.png



So, what is their "rated power", then?? And do the OEM manufacturers-assemblers make the serious test and specify the rated power, or just point to the module datasheet?
 
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It quickly went into protection and never worked again in BTL mode at 8 ohm load…
May I ask - was it the speaker load and which speaker it was?

The reason why I ask is that we have discussed only power parameters with pure resistive load so far. And, the situation becomes much more complicated with the complex load, and we have unfortunately no standards for it.
 
It was tested at 250W into 8 ohm resistive load in BTL mode, which destroyed the amp after a few seconds.
The test signal was that "Interstellar Black Hole" track discussed above.

8 ohm resistive load with both channels driven worked fine, and the amp was indeed able to deliver sustained output of 2x250W.
 
It was tested at 250W into 8 ohm resistive load in BTL mode, which destroyed the amp after a few seconds.
The test signal was that "Interstellar Black Hole" track discussed above.

8 ohm resistive load with both channels driven worked fine, and the amp was indeed able to deliver sustained output of 2x250W.
Wow! I tested the NC2525MP in the BTL mode with 4 ohm resistive load
and it worked fine, reaching 400W/4ohm in a stepped level test at 1kHz. Maybe the large heatsink that I use, 135mm x 390mm with about 0.6K/W temperature coefficient saved the module. I only hope it was not that my test that encouraged you to try the BTL.

Note: now I see you tested the NC502MP, a different module. Wow, and they specify “
Output Power (8Ω):2 x 350W, (1 x 1200W in BTL)
Again, what a shame.

Note2: Ralph Nader needed for audio. Me is the weak cup of tea :).
 
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Wow! I tested the NC2525MP in the BTL mode with 4 ohm resistive load
and it worked fine, reaching 400W/4ohm in a stepped level test at 1kHz. Maybe the large heatsink that I use, 135mm x 390mm with about 0.6K/W temperature coefficient saved the module. I only hope it was not that my test that encouraged you to try the BTL.
Have a look at the thread that he's testing the gear,he uses large heatshinks too (hence the results,some reach 2kW)
 
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I agree with the need for honest measurements. I'm glad for the new FTC rules, and definitely appreciate your time and effort in testing.

But I also think that in all fairness to some of these amps, if their ratings were created prior to the FTC rules that the reports should state that very clearly. In other words, you're expecting them to pass a test that they never claimed they would pass. As a consumer I appreciate knowing that the amp doesn't meet the expectations implied by the FTC, but it's unfair to the engineers who created these products to say they are failing when they never claimed that they would pass

The amplifier rule is not "new". It's been around since 1974.

The "new" rule is just a few amendments which go about cleaning up the language and a couple of other minor changes, none of which change the basic requirements much at all.

There are no excuses to be had- the advertising requirements have been known for 50 years! What the FTC has done is re-iterate the Rule and that likely means they will take a dim view of non-compliance when it is drawn to their attention.

The issue is ongoing and the same as it was in the early 1970s. Manufacturers inflate their claims, tell lies and try as hard as they can to skirt requirements. Sellers and assemblers do the same thing and continue to do so. Amplifiers are sold on power output. Bigger numbers sell more.
 
It was tested at 250W into 8 ohm resistive load in BTL mode, which destroyed the amp after a few seconds.
The test signal was that "Interstellar Black Hole" track discussed above.

8 ohm resistive load with both channels driven worked fine, and the amp was indeed able to deliver sustained output of 2x250W.
The dynamics and transients from the test track would be more challenging than a steady-state signal, right?
 
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FWIW, I've been running two now-elderly A07s (with 50VDC rated Nichicon shunt capacitors) on somewhere between 46 and 47 volts for nearly four years with no problems at all -- not even a single protection incident, let alone an outright failure.

Patience. This type of failure comes suddenly, and only once.
 
Compliance with FTC rule is not free. Let's say the amp can only run for 1 minute at the stated power level instead of 5. To make it compliant, you would either need a fan, a larger heatsink or both. The former has a major disadvantage in noise and reliability as the fan fails. The latter increases cost (both in material and shipping). Are you willing to have every amplifier's cost be increased this way?

Also keep in mind that any fluff spec is identified in measurements I do. So people here are not being sold junk specs.
 
I believe there are two perspectives on this issue.

Let's say an amplifier does not pass the FTC test at the claimed or expected output.

Solutions:
  1. The amplifier could be redesigned to achieve the desired output, which would increase costs.
  2. Alternatively, the amplifier could be de-rated to a level that complies with the FTC standard, which would not lead to an increase in costs.
I don't think there's more to it.
 
Compliance with the rule is actually zero cost, or to be correct it costs the time of the person who will change the figure at the web page,manuals,etc.
I can add some additional cost for testing but the ones that go for the numbers already know the results,most of them are members in diyaudio which has scrutinized this subject to death for years and remember even legal actions against power claims.
 
Compliance with FTC rule is not free. Let's say the amp can only run for 1 minute at the stated power level instead of 5. To make it compliant, you would either need a fan, a larger heatsink or both. The former has a major disadvantage in noise and reliability as the fan fails. The latter increases cost (both in material and shipping). Are you willing to have every amplifier's cost be increased this way?

Also keep in mind that any fluff spec is identified in measurements I do. So people here are not being sold junk specs.
One advantage though is a consistent test standard to be applied accross all devices.

A manufacturer is free to state it provides RatedWatts complying to FTC, but can then in addition (smaller text according to the marking part of the standard) Provide TransientWatts for TimeSeconds, and/or HeadroomWatts for TimeMinutes (together with whatever recovery times apply) for those people who recognize that no music needs full power continuously, and would like to understand what transients and crescendos can be accommodated without clipping.

That is the sort of information I'd like manufacturers to be providing.

I'd also like them to be protecting the amp, not only based on instantaneous current limits, but some form of software modeled thermal performance which understands how much heat is being put into the thermal design for any given load, and protects then based on a realistic assessment of actual temperatures.

None of this should be expensive with modern microcontroller controlled and monitored designs. It would also sort out the grownups in the room from the tinker kids.
 
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It sometimes happens that an amplifier rated "Output Power 100W @4Ω THD+N<1%" dies within 3 seconds of pushing 33 watts into a 4 ohm load:
- https://www.audiosciencereview.com/...ping-b100-amplifier-review.57036/post-2149364

If testing an amplifier for 5 minutes at rated power is too much, then perhaps testing it for at least 5 seconds would tell us more about an amplifier than just a few milliseconds, as it is currently done with "Power Versus Distortion" measurements.
 
So may I ask you, according to your opinion, Hypex NC252MP rated power is 2 x 50W/4ohm ? If this is your suggestion, then I have no objections and confirm that the amp passed the test easily.
I'm not sure which is why I asked. Even the 50W was ambiguous about Ohm , was it 2/4/8 ?

....
But, what would be this, then?
1733256216977.png

A "hausnummer"? It should not be
Just more confusion . That should be stated as max output power. Since these go to OEM builders I'm hoping they would know and their final product gives accurate information to their product which is the purpose of the new testing guidelines?
 
  1. The amplifier could be redesigned to achieve the desired output, which would increase costs.
  2. Alternatively, the amplifier could be de-rated to a level that complies with the FTC standard, which would not lead to an increase in costs.
I don't think there's more to it.

1. not gonna happen because of economical reasons.
2. marketing department not gonna let it to do. You can force it by politicians but that's an another rats nest.

I think the best solution would be to put the FTC rating into the datasheet and tech savvy people will have the chance to see it. Hypex includes the continues power rating which is a good sign imho.

Honestly normal people needs years or even decades to adjust and accept they need only 5-50W of amplification in their average room.
 
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