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

[pma]

"pre-conditioning was at 2 x 8W/4ohm for one hour, as requested by the FCT document"
Source: https://pmacura.cz/FCT/aiyima_a07_test.htm

the load should be 8 ohms according the FTC requirement ... or not?

Apples and oranges. Your link goes to test with the 27V PSU, which the amp passes easily. In post #584 I spoke about former test with 50V (48V) PSU, when the amp shut down after one minute when driven in one channel only at 1/2.5 fraction of the advertised power. It was also mentioned here several times. Again, it would lead to derated power or reduced PSU voltage range. This debate is completely frustrating.

 

[pjug]

Please let us quote the FTC regulation correctly, to prevent further second guessing debates. There is nothing like "test should be performed at each frequency", it states that "rated power should be obtainable at ..."

How is the bolded below not requiring full power for five minutes at multiple frequencies?

Rated power shall be obtainable at all frequencies within the rated power band without exceeding the
rated maximum percentage of total harmonic distortion after input signals at said frequencies have been
continuously applied at full rated power for not less than five (5) minutes at the amplifier's auxiliary input,
or if not provided, at the phono input.

 

[Sokel]

Isn't the FTC test specified at 8 ohms load? Perhaps you can do your test again at 8 ohms. I would wager it lasts just fine for 5 minutes.
In which case it would pass the FTC test and the consumer would be misled into thinking all is golden. Are you starting to see why the test doesn't achieve your desired objectives or its own intent?

I agree to this.
The utmost important section should be the tests conditions to the last detail.
We don't even know what signal to use!

 

[pjug]

Isn't the FTC test specified at 8 ohms load? Perhaps you can do your test again at 8 ohms. I would wager it lasts just fine for 5 minutes.
In which case it would pass the FTC test and the consumer would be misled into thinking all is golden. Are you starting to see why the test doesn't achieve your desired objectives or its own intent?

To be fair, the title of the thread says "with respect to FTC" not "in accordance with FTC".

 

[Old_School_Brad]

This isn't a technical standard. No one has any obligation to adhere to it. It's only jurisdiction is in the advertising copy of products within the US. In this globalised marketplace the rule is unenforceable.
A 5 minute stress test tells you nothing. What if an amp goes into protection after 6 minutes under those 8 ohm load conditions? It would still be a failure as far as a consumer is concerned, but now they have been misled into thinking all is golden because it passed the FTC test. So you better do it for several hours just to make sure the amp has reached thermal equilibrium. What if it fails when loaded at 4 ohms? A more realistic load for today's speakers? Thats not tested. And so on.
The FTC test isn't just a bit flawed, it's terminally dysfunctional. The intent is good, the implementation is grossly misinformed.

All entities marketing amplifiers in the U.S. are legally obligated to comply with these standards.

Failure to adhere to the FTC amplifier rule can result in warnings, fines, or even the prohibition of the product’s importation or sale in the market.

A 5-minute stress test provides significantly more insight than a 20 ms burst. It evaluates the amplifier’s thermal design while monitoring its behavior, stability, and THD+N. Critics need to decide: is the test too rigorous or too lenient?

There are always "what ifs." For example, what if your advertised 100 W continuous amplifier can only sustain 20 W? From a consumer’s perspective, having this information is invaluable.

As for thermal equilibrium, that’s exactly what the initial low-power sequence is designed to address. With a properly designed passive convection heatsink, this soak test may even benefit the amplifier. By the time the 5-minute full-power test begins, the heatsink is preheated, and airflow is already active due to the temperature gradient. Running a full-power test immediately upon startup would likely pose a higher risk, as there would be no airflow yet to dissipate heat effectively.

Regarding the use of a more “realistic” load, a standard must be established somewhere. While I might personally prefer a 4-ohm resistive load or even a model like the Infinity Kappa 9 (kidding!), the reality is no single test can perfectly mimic the diverse variables of real-world setups. The objective isn’t to create a flawless test -perfection is unattainable. Instead, the goal is to provide a consistent benchmark for comparison and accountability. That’s the very purpose of standards.

 

[pjug]

OK, so are you saying we need appropriate testing to identify relevant issues? Otherwise my reading was that PMA was citing his testing with specific reference to the FTC tests.

sorry I was just goofing about the language. You would have to ask @pma

 

[pma]

Regarding the use of a more “realistic” load, a standard must be established somewhere. While I might personally prefer a 4-ohm resistive load

But this is definitely not excluded. Let me quote:

Whenever any direct or indirect representation is made of the power output, power band or power
frequency response, or distortion characteristics of sound power amplification equipment, the following
disclosure shall be made clearly, conspicuously, and more prominently than any other representations or
disclosures permitted under this part: The manufacturer's rated minimum sine wave continuous average
power output, in watts, per channel (if the equipment is designed to amplify two or more channels
simultaneously) at an impedance of 8 ohms, or, if the amplifier is not designed for an 8-ohm impedance,
at the impedance for which the amplifier is primarily designed, measured with all associated channels
fully driven to rated per channel power. Provided, however, when measuring maximum per channel output
of self-powered combination speaker systems that employ two or more amplifiers dedicated to different
portions of the audio frequency spectrum, such as those incorporated into combination subwoofersatellite
speaker systems, only those channels dedicated to the same audio frequency spectrum should
be considered associated channels that need be fully driven simultaneously to rated per channel power.

For example, I design amplifiers primarily for 4-ohm impedance, and any higher. The 8-ohm test is then always easier to pass than the 4-ohm test. And the test must be performed at 4-ohm then.

Last: IMO amplifier must be able to yield rated power as a continuous power without any time limitations. Again and again, peak power, music power or whatsoever is not a rated power.

 

[Old_School_Brad]

But this is definitely not excluded. Let me quote:



For example, I design amplifiers primarily for 4-ohm impedance, and any higher. The 8-ohm test is then always easier to pass than the 4-ohm test. And the test must be prformed at 4-ohm then.

Last: IMO amplifier must be able to yield rated power as a continuous power without any time limitations.

Thanks, I haven't noticed that.

 

[SIY]

What if it fails when loaded at 4 ohms?

Or, more reasonably, when power factors are not unity. You know, like actual speakers people use.

 

[SIY]

So what use is the FTC test?

Some people need Daddy to tell them what to do.

 

[Old_School_Brad]

The low power sequence doesn't do this, especially with a class d amp. an amp may not reach shutdown temp until after the 5 minutes.
You are correct. the 8 ohm resistive load specified in the FTC test is wholly unrepresentative of modern real world speaker loads. So what use is the FTC test?

It could be helpful for you to take your time and read through all the posts more thoroughly.

 

[JustJones]

These are the old regulations.

The manufacturer's rated minimum sine wave continuous average power output, in watts, per channel (if the equipment is designed to amplify two or more channels simultaneously) at an impedance of 8 ohms, or, if the amplifier is not designed for an 8-ohm impedance, at the impedance for which the amplifier is primarily designed, measured with all associated channels fully driven to rated per channel power.

https://www.govinfo.gov/content/pkg/CFR-2009-title16-vol1/xml/CFR-2009-title16-vol1-sec432-2.xml

These are the new regulations

Federal Register :: Request Access

www.ecfr.gov

 

[JustJones]

But this is definitely not excluded. Let me quote:



For example, I design amplifiers primarily for 4-ohm impedance, and any higher. The 8-ohm test is then always easier to pass than the 4-ohm test. And the test must be performed at 4-ohm then.

Last: IMO amplifier must be able to yield rated power as a continuous power without any time limitations. Again and again, peak power, music power or whatsoever is not a rated power.

You're quoting the outdated old regulations there is no qualification to use 4 Ohm or any other than 8 Ohm in the new regulations.

 

[Old_School_Brad]

These are the old regulations.

https://www.govinfo.gov/content/pkg/CFR-2009-title16-vol1/xml/CFR-2009-title16-vol1-sec432-2.xml

These are the new regulations

Federal Register :: Request Access

www.ecfr.gov

Thanks. 8 ohm only.

 

[antcollinet]

Working with VSD's and and other power electronics. These operates 24/7 365 close to full continues power with sine waves for decades without blowing up ?

Your typical VSD has a switching frequency of 4kHz - 1/100th that of a typical class D amp. It still needs a bloody great heatsink, and noisy fan blowing over that heatsink to dissipate the heat.

I will give you that they are switching higher voltages, which will increase the switching losses but reduce the "on state" losses.

 

[pma]

"pre-conditioning was at 2 x 8W/4ohm for one hour, as requested by the FCT document"
Source: https://pmacura.cz/FCT/aiyima_a07_test.htm

the load should be 8 ohms according the FTC requirement ... or not?

I have just finished the FTC preconditioning test with AIYIMA A 07, the ASR recommended amplifier

AIYIMA A07 - an attempt to make a FTC test with 48V power supply

1. Test conditions:

The manufacturer claims 180-190Wpc into 8ohm load with the 48V power supply (set exactly to 48.0V)

So, the preconditioning was done at 23.75W/8ohm per channel, both channels driven.

It started well with low distortion and continued for 12 minutes. The amplifier has shut down after 12 minutes.

The amplifier failed to pass the one hour preconditioning at 1/8 power, it failed and shut down after 12 minutes. This recommended component even did not pass the preconditioning.

How to fix - derate maximum supply voltage to 36V.

The thermal design of the amplifier is absolutely improper with respect to recommended range of power supplies.

P.S.: I absolutely concur with @restorer-john opinion on @amirm ASR amplifier tests and recommendations expressed in those tests.

AIYIMA A07 amplifier 48V PSU test

 

[SIY]

How to fix - derate maximum supply voltage to 36V.

So reduce its usefulness for the intended purpose. Well, it handicaps consumers but it makes you happy. Fair trade-off, right?

 

[Old_School_Brad]

I have just finished the FTC preconditioning test with AIYIMA A 07, the ASR recommended amplifier

AIYIMA A07 - an attempt to make a FTC test with 48V power supply

1. Test conditions:

The manufacturer claims 180-190Wpc into 8ohm load with the 48V power supply (set exactly to 48.0V)

So, the preconditioning was done at 23.75W/8ohm per channel, both channels driven.
View attachment 413123
It started well with low distortion and continued for 12 minutes. The amplifier has shut down after 12 minutes.

The amplifier failed to pass the one hour preconditioning at 1/8 power, it failed and shut down after 12 minutes. This recommended component even did not pass the preconditioning.

How to fix - derate maximum supply voltage to 36V.

The thermal design of the amplifier is absolutely improper with respect to recommended range of power supplies.

P.S.: I absolutely concur with @restorer-john opinion on @amirm ASR amplifier tests and recommendations expressed in those tests.

So. Its size constraints make it a 20 W continous amplifier.

 

[RickS]

I have just finished the FTC preconditioning test with AIYIMA A 07, the ASR recommended amplifier

AIYIMA A07 - an attempt to make a FTC test with 48V power supply

1. Test conditions:

The manufacturer claims 180-190Wpc into 8ohm load with the 48V power supply (set exactly to 48.0V)

So, the preconditioning was done at 23.75W/8ohm per channel, both channels driven.
View attachment 413123
It started well with low distortion and continued for 12 minutes. The amplifier has shut down after 12 minutes.

The amplifier failed to pass the one hour preconditioning at 1/8 power, it failed and shut down after 12 minutes. This recommended component even did not pass the preconditioning.

How to fix - derate maximum supply voltage to 36V.

The thermal design of the amplifier is absolutely improper with respect to recommended range of power supplies.

P.S.: I absolutely concur with @restorer-john opinion on @amirm ASR amplifier tests and recommendations expressed in those tests.

Where did Amir recommend this amp or did you mean A70?

 

[Zek]

Where did Amir recommend this amp

Look here

AIYIMA A07 TPA3255 Review (Amplifier)

This is a review and detailed measurements of the AIYIMA A07 desktop amplifier based on TPA3255 class D amplifier chip. It was kindly purchased new by a member and drop shipped to me. The cost is US $72 on Amazon including prime shipping. And as of this shipping, it also included a 32 volt, 5...

www.audiosciencereview.com