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

[amirm]

Here's a series of tests Perreaux required in the S/M for one of their baby power amplifiers, the PMF-2150B (200W+200W I listed further back in this thread) that would likely vaporize most of the little pretend watt boxes Amir likes so much.

There is zero mention of it running at full power for 5 minutes. The TO-3 transistors are laying flat instead of properly being mounted on the side heatsinks. The thermal impedance as a result, is much higher, necessitating that fan in the back. The fan is poorly located with no fluid dynamics analysis for proper air circulation. To be sure, it does a lot more than nothing but not remotely proper.

Get a modern PA amp and it too, with a fan, will run reliably, producing gobs more power than it. And it would sell for a fraction of what that amp cost.

And oh, they break down as well, lest you once again be claiming that the older amps didn't break. Here is a quick google search: https://www.diyaudio.com/community/threads/perreaux-8000c-left-channel-not-working-need-help.325666/

"I have a Perreaux 8000c ..lately the left channel started to get crackly and staticky and also little pop sounds .I have to mention that I have 3 6000c as well that have very similar symptoms "

To claim that the older amps didn't break is absurd. The only thing more absurd is claiming that after decades, they are still reliable. All amplifiers break. I actually trust the class D ones far more because a) they run so much cooler and b) they are so easy to repair with a module swap.

 

[JustJones]

In the manual the MC 462 shows the required specs for the old regulations which should be sufficient even though it still falls short since it doesn't mention the FTC in the manual. If the FTC tries something idiotic like making the new rule retroactive then they'll bite off more than they can chew.

 

[KSTR]

Apologies for my ignorance but it seems to me that a continuous power rating is quite important, and I get that the FTC regs are flawed. What would be better/more realistic?

My go-to test would be: does an amp deliver in a "drunk students' party scenario" in a hot summer night, volume turned up to the point of audible clipping most of the time, for hours. Especially for those lower powered amps.

That's a pretty realistic and demanding scenario and it always was. Back in my student days, early 80'ies, when we did such parties with the rubbish cheap hifi stuff we could afford people were asked to bring spare amps in case one shuts down and needs some cooling, also we brought fans for exactly that reason. Remember in these days recorded music still had lots of dynamics and much less bass than today...

When looking at the exact technical details of power rating methods it becomes clear that this is complicated matters. Point is, what assumptions about what conditions are deemed realistic for the assumed use cases? Audio power amps are not universal laboratory 4-quadrant AC power-supplies were specification requirements are very stringent but also very clear. Therefore compromises and assumptions have to be made and the attempt to boil everything down into one or two simple spec numbers laypeople can easily compare is basically doomed to fail, more or less.

 

[Old_School_Brad]

I believe an amplifier should be capable of delivering its full rated power for five minutes without sustaining damage. I don't think that's too much to ask for.

 

[gnarly]

And that leads us right back to how those ratings were determined...

Yep. I think the idea of wanting a single number rating is at the root of the problem
An amp simply can't be described that way imo.
It's ability to deliver power we know is a short to medium term function of time and load. And a longer term function of thermal capacity.

What I'd like to see, is power into given standard loads, 2/4/8 ohm, at various time intervals representing real world continuous and burst, time periods.

For non-thermal continuous and burst ratings:
I could live with 15 seconds as a proxy for continuous duration, because that exceeds any time period I've ever used for attack settings on RMS limiters for subs.
Worst case duty, although I would like to see something like one of the CEA 2006-B methods, or whatever best replicates the attack/release time of largest RMS limiters.
Also, the attached chart CAF rating method's footnote claims 15 sec is an empirically derived duration for measuring..... without damaging the amp.

I could live with 20ms as a proxy for burst duration. It is a commonly recognized peak limiter attack time for subs < 63Hz. Which means it can most like handle peak voltage and duration settings throughout the rest of the spectrum.

The idea behind both of those continuous and peak times, is that I at least want to be able to choose an amp to be able to reach the driver's (well chosen limiters),
and then 'why do I want more past that?"

As far as a thermal rating, I would like to see max wattage derived as 1/8th of the whatever wattage can run forever, again into 2/4/8 ohm loads.
Using pink with a standard 12 dB crest factor (which will have most all amps showing occasional light clipping.)
It would be nice know same derived rating for 3dB and 6 dB crest factors as well, (which will obviously derate the amp), but I could live without them and estimate.

Two footnotes: would really rather all specs were Voltage, yeah...which is probably the most wishful thinking yet.
and the "limiter usage gives amp needs logic" isonly appropriate for active multi-ways.
Passives are a bitch to amp properly imo. Need much bigger amps than realized, and can't implement limiters easily if at all.

fromhttps://caf.prosoundtraining.com/comparison-of-standards-for-amplifier-power-ratings/#tab-id-2

 

[Chr1]

Yep. I think the idea of wanting a single number rating is at the root of the problem
An amp simply can't be described that way imo.
It's ability to deliver power we know is a short to medium term function of time and load. And a longer term function of thermal capacity.

What I'd like to see, is power into given standard loads, 2/4/8 ohm, at various time intervals representing real world continuous and burst, time periods.

For non-thermal continuous and burst ratings:
I could live with 15 seconds as a proxy for continuous duration, because that exceeds any time period I've ever used for attack settings on RMS limiters for subs.
Worst case duty, although I would like to see something like one of the CEA 2006-B methods, or whatever best replicates the attack/release time of largest RMS limiters.
Also, the attached chart CAF rating method's footnote claims 15 sec is an empirically derived duration for measuring..... without damaging the amp.

I could live with 20ms as a proxy for burst duration. It is a commonly recognized peak limiter attack time for subs < 63Hz. Which means it can most like handle peak voltage and duration settings throughout the rest of the spectrum.

The idea behind both of those continuous and peak times, is that I at least want to be able to choose an amp to be able to reach the driver's (well chosen limiters),
and then 'why do I want more past that?"

As far as a thermal rating, I would like to see max wattage derived as 1/8th of the whatever wattage can run forever, again into 2/4/8 ohm loads.
Using pink with a standard 12 dB crest factor (which will have most all amps showing occasional light clipping.)
It would be nice know same derived rating for 3dB and 6 dB crest factors as well, (which will obviously derate the amp), but I could live without them and estimate.

Two footnotes: would really rather all specs were Voltage, yeah...which is probably the most wishful thinking yet.
and the "limiter usage gives amp needs logic" isonly appropriate for active multi-ways.
Passives are a bitch to amp properly imo. Need much bigger amps than realized, and can't implement limiters easily if at all.

fromhttps://caf.prosoundtraining.com/comparison-of-standards-for-amplifier-power-ratings/#tab-id-2

View attachment 413688

Thanks. I would like to see more of this.

ie people in the know here suggesting viable alternatives to the FTC regs.
Obviously it's very unlikely everyone will agree on everything, but I think it would be more constructive than the constant arguing about the FTC requirements. Presumably most folks think that it's not great having manufacturers being able to state any old power ratings they like... My 2c.

 

[Kapoen]

Hypex seems to have made a statement on the FTC requirements; https://www.regulations.gov/comment/FTC-2024-0039-0096

 

[Maciekw]

Hypex seems to have made a statement on the FTC requirements; https://www.regulations.gov/comment/FTC-2024-0039-0096

Reading this document with understanding should close this ineffective yet emotional discussion.

 

[Chr1]

Hopefully adjustments/compromises can be made and good regulation leads to happier consumers and manufacturers alike... Please.

 

[Sokel]

The 12.5 W instead of 500W rating when measured and rated at 20kHz that hypex says is primarily because of the early reach of 1% THD+N I think.
(I did read the capacitor limitations,etc)
But at what measuring BW?Is it specified?

 

[Sokel]

Out of curiosity I had a read to what LG thinks about it (as a company with many recourses) and it's interesting that their only concern is about the retroactive aspect of the law (makes sense from their point of view) .
Not a word about specs,conditions,etc.

 

[mhardy6647]

McIntosh have been specifying their gear in accordance with the Amplifier Rule since 1974. They have never wavered AFAIK. Conservative specs too.

I think Mac's specified continuous power capabilities (if not including the letter of the "FTC '74" preconditioning requirement) since the 1950s -- possibly from "day one" of the company (early 1950s).


Not their first product(s), nor their first advertisement, but illustrative of their early and complete adoption of realistic power claims.

 

[JustJones]

One from JEITA

Regulations.gov

www.regulations.gov

Masimo

Regulations.gov

www.regulations.gov

Harman

Regulations.gov

www.regulations.gov

 

[RickS]

Another look at how the FTC missed the mark failing to consider amplifier transition to Class D...

Class D is already more than twice the market of Class AB and is forecast to outgrow it significantly. Was surprised to see that AB is forecast to continue to grow. This chart is from a free teaser, so would need $4000 for the full report. It might explain where the Class AB growth is. The consumer amplifier market is a large share, so would expect substitution to Class D to reduce its share. It is in dollars so unit sales might offer some insight.

I also tried to find how long it took for the pro market to transition to Class D (often a leading indicator for consumer market) but came up empty. If anybody has this info, please share. Even if no market share, maybe somebody buying pro amps would know.

 

[Sokel]

Another look of how the FTC missed the mark failing to consider amplifier transition to Class D...

View attachment 413722

Class D is already more than twice the market of Class AB and is forecast to outgrow it significantly. Was surprised to see that AB is forecast to continue to grow. This chart is from a free teaser, so would need $4000 for the full report. It might explain where the Class AB growth is. The consumer amplifier market is a large share, so would expect substitution to Class D to reduce its share. It is in dollars so unit sales might offer some insight.

I also tried to find how long it took for the pro market to transition to Class D (often a leading indicator for consumer market) but came up empty. If anybody has this info, please share. Even if no market share, maybe somebody buying pro amps would

What are the "others" on the chart?

 

[amirm]

Reading this document with understanding should close this ineffective yet emotional discussion.

Indeed. Yet FTC counted that comment as one of 551 in favor of its regulation!

 

[amirm]

What are the "others" on the chart?

Maybe Class H, G, etc.

 

[amirm]

I believe an amplifier should be capable of delivering its full rated power for five minutes without sustaining damage. I don't think that's too much to ask for.

Doing what exactly? Playing sine waves? If so, go ahead and run that test and see how loud you can tolerate it and then run it for 5 minutes. Report back if amp goes into protection or dies.

If you mean playing music, then do the same and report on that.

Amplifiers are simply not shutting down for people after 5 minutes of playing music or they wouldn't be able to sell much or any.

 

[amirm]

Adding on, the capabilities that FTC wants in the amplifier will damage just about any tweeter out there in your speakers. So even if you can tolerate the loudness, your speaker won't at 1+ kHz.

 

[Timcognito]

Another look of how the FTC missed the mark failing to consider amplifier transition to Class D...

View attachment 413722

Class D is already more than twice the market of Class AB and is forecast to outgrow it significantly. Was surprised to see that AB is forecast to continue to grow. This chart is from a free teaser, so would need $4000 for the full report. It might explain where the Class AB growth is. The consumer amplifier market is a large share, so would expect substitution to Class D to reduce its share. It is in dollars so unit sales might offer some insight.

I also tried to find how long it took for the pro market to transition to Class D (often a leading indicator for consumer market) but came up empty. If anybody has this info, please share. Even if no market share, maybe somebody buying pro amps would

Without derailing this discussion that is over my head, is class B really an embodiment of that size or at all? examples?