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

[gnarly]

I don't think this thread has explicitly answered your question, but Amir gave me the answer below when I asked the same question a few years back -> https://www.audiosciencereview.com/...lifier-with-sinad-over-120.31305/post-1151445.

View attachment 413484

Michael

Thanks Michael. That's the info i was looking for.....out of curiosity.
Sounds to me like the process of establishing max power VS some set level of max distortion, is what makes the process iterative and somewhat difficult.
Also sounds like full power doesn't take place much, past that determination. Dunno how accurate that is, but i find it interesting...

 

[pjug]

On the flip side of non-compliance, are companies that do comply going to give it prominent mention in their literature? (looks like ATI does, not sure who else) Or is the rule considered so irrelevant that even those that comply don't think it is much of a badge of honor.

 

[Rick Sykora]

I expect many are fine with Pavel testing however and whatever he wants.

In the spirit of the season, peace and health to all!

Best wishes,

Rick

 

[Mschn]

Because hi-fi was very expensive then. And very profitable. Today, the same companies lose money on most of their hi-fi line. When I asked the top executives of those companies why they still sell them the answer was that of national pride. That it would be embarrassing for Japan to get out of AV business. This is the heatsink in Sony AVRs:

You think this folded steel, cheap heatsink will be happy during max power testing for 5 minutes???

Why not? The conductivity of the metal in a heat-sink is not the limiting factor. For natural convection cooling the metal-to-air interface is critical. A heavy heat-sink adds thermal mass which is good for handling short-term power surges. But, I suspect the main reason for going down that design route is to impress customers.

/Martin
PS My guess for the structure shown above is folded sheet aluminium.

 

[Old_School_Brad]

Why not? The conductivity of the metal in a heat-sink is not the limiting factor. For natural convection cooling the metal-to-air interface is critical. A heavy heat-sink adds thermal mass which is good for handling short-term power surges. But, I suspect the main reason for going down that design route is to impress customers.

/Martin
PS My guess for the structure shown above is folded sheet aluminium.

It’s perfectly fine -cheap in appearance but highly effective. It offers more surface area than you’d expect, and Yamaha has successfully utilized these for decades in power amplifiers, integrateds and receivers.

 

[Chr1]

I agree. If vented properly this will work very well. Not as sturdy or aesthetically pleasing as cast or extruded aluminium, so best used internally.
But, like a car radiator, should work well, given correct venting and decent air flow.

(Mechanical engineering being more my thing than electrical.)

 

[gnarly]

Isn't that interesting? It seems these plates work after all.
And it is not a surprise, as even the craziest action movie does not have extended explosions for hours. So the plate amp has only to provide for (fractions of) seconds once in a while.
It would be different, if it were to drive a massage chair on full power for a whole session, but that is not what audio is about. On the other hand, a close up jackhammer video might get the amp into trouble. So maybe it is a question of taste in the end. But even with a jackhammer the average power will be much less than peak power.

And for subs, it needs a VERY big driver to not bottom out at 20 Hz with 14A_peak, which is what the Hypex will deliver (at 1% THD) at ≈ 400W (=2x200W)/4Ω.

I don't think these plates work for subs.....if using the Hypex NC252MP posted in #793 as a general example.
Both channels driver @ 4 Ohm, show 122W max at 20Hz. Or only 5.5A.

And it doesn't take a very big driver to need 200W.
I use an 8 ohm 4" driver, midrange from150-200Hz up, that optimally needs at least a 150W amp. And that doesn't even get it up to xmax, certainly not bottoming out x-damage.

Plus, we tend to forget that amps typically have next to no headroom above their rated/claimed specs.
So imo/ime, it's simply a non starter for a sub.

 

[Old_School_Brad]

I agree. If vented properly this will work very well. Not as sturdy or aesthetically pleasing as cast or extruded aluminium, so best used internally.
But, like a car radiator, should work well, given correct venting and decent air flow.

(Mechanical engineering being more my thing than electrical.)

Yes. A lightweight heat sink like this one may even outperform an extruded aluminum heat sink in convection efficiency. Its thin, foil fins provide a larger surface area and lower mass, making it highly effective at dissipating heat into the air. However, extruded solid heat sinks are generally better at conducting heat directly from the transistors to the base plate due to their one-piece, solid design.

That said, the smaller thermal mass of the lightweight model can lead to greater temperature fluctuations, while the solid extruded heat sink, with its larger mass, ensures more stable temperature behavior. Ultimately, the choice depends on the specific application, design requirements, and dimensions.
It's not accurate to claim that one is definitively better than the other.

 

[Chr1]

Indeed. But either is better than none at all.
(Hence the thermal fragility of desktop amps!)

 

[Old_School_Brad]

...
Plus, we tend to forget that amps typically have next to no headroom above their rated/claimed specs.

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

 

[amirm]

Mcintosh seems to follow the rule?
Is that how is supposed to be?

View attachment 413613

McIntosh MC462 Stereo Amplifier

Experience stereo bliss with the MC462 Amplifier. It features a robust output of 450 Watts per channel. With a dedicated McIntosh Autoformer™ connected to each audio channel, the full 450 Watts is available to any speaker regardless if it has 2, 4 or 8 Ohm impedance. Just one MC462 Amplifier can...

www.mcintoshlabs.com

No. It violates both the old rule and certainly new. Old rule requires specifying the distortion level and bandwidth which it lacks. New rule requires 5 minute run time which is certainly missing. It could very well go into protection on such extreme test.

 

[Chr1]

I am curious if five minutes is excessive, what would be a more acceptable time for such a test?

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?

 

[Sokel]

No. It violates both the old rule and certainly new. Old rule requires specifying the distortion level and bandwidth which it lacks. New rule requires 5 minute run time which is certainly missing. It could very well go into protection on such extreme test.

I see the test Erin did and it seems he has a "continuous" power figure:

(it seems like a really nice amp)

	2-Ohm	4-Ohm	8-Ohm
	Left	Right	Left	Right	Left	Right
Max Continuous Output at 0.01% THD+N (watts)	564.2	573.4	502.7	501.7	494.7	493.9
Max Continuous Output at 1.00% THD+N (watts)	605.2	640.9	545.8	547.5	537.9	540.9
Peak Power at 1.00 THD+N (watts) (CEA-2006/490A)	828.4	847.7	823.4	821.8	793.6	792.4

McIntosh MC462 Stereo Amplifier Review

McIntosh MX100 A/V Processor Review

www.erinsaudiocorner.com

 

[JustJones]

Mcintosh seems to follow the rule?
Is that how is supposed to be?

View attachment 413613

McIntosh MC462 Stereo Amplifier

Experience stereo bliss with the MC462 Amplifier. It features a robust output of 450 Watts per channel. With a dedicated McIntosh Autoformer™ connected to each audio channel, the full 450 Watts is available to any speaker regardless if it has 2, 4 or 8 Ohm impedance. Just one MC462 Amplifier can...

www.mcintoshlabs.com

For approximately 50% of the price, more Watts and a lot lighter 9.8kg

• FTC Power Output Rating500 W
• Power Output per Channel500 W into 8 ohms
  800 W into 4 ohms
• Number of Channels2
• Total Harmonic Distortion0.05%
• S/N below rated output98dB
• Dynamic Headroom8 ohms: 2.7dB
  4 ohms: 3.7dB
• Damping Factor8 ohms: >85
  4 ohms: >45
• Rated Power Band20Hz to 20kHz
• Frequency Response+0, -0.9dB from 20Hz to 20kHz

McIntosh MI502 2-Channel Digital Amplifier

A welcome addition to a custom installed home audio or home theater system.

www.mcintoshlabs.com

 

[Sokel]

For approximately 50% of the price, more Watts and a lot lighter 9.8kg

• FTC Power Output Rating500 W
• Power Output per Channel500 W into 8 ohms
  800 W into 4 ohms
• Number of Channels2
• Total Harmonic Distortion0.05%
• S/N below rated output98dB
• Dynamic Headroom8 ohms: 2.7dB
  4 ohms: 3.7dB
• Damping Factor8 ohms: >85
  4 ohms: >45
• Rated Power Band20Hz to 20kHz
• Frequency Response+0, -0.9dB from 20Hz to 20kHz

McIntosh MI502 2-Channel Digital Amplifier

A welcome addition to a custom installed home audio or home theater system.

www.mcintoshlabs.com

I like Purifi too!

 

[JustJones]

I always wanted a big McIntosh but could never afford one , now I couldn't lift one.

 

[Joe Smith]

Well at that price - and weight - it better be a pretty nice amp!

I have a lot of respect for that level of engineering, but it does come at a price. For many of us, these amps in the $75 - 1,000 price range have to be "good enough".

I don't like buying junk that breaks in a year or two, but my inexpensive D amps have all been pretty robust thus far. But then I play at very moderate listening levels.

If money were no object and I was buying new and something for higher power levels, I would definitely choose the Benchmark amp over a Mac at 3x the price, though.

I like that a few of my vintage pieces of equipment got refurbished and will be good for the rest of my life, but I've stopped looking at everything I own needing to be like that.

I believe in matching the equipment need to task at hand. For very large rooms, playing at very high volume levels, going up the amp chain probably a good idea rather than fiddling around with Fosi and Aiyima monoblocks.

But that's just me...

 

[amirm]

I see the test Erin did and it seems he has a "continuous" power figure:

Those are the same tests I run. "Continuous" means a steady state sine wave as opposed to burst of sine wave. I show both in my power measurements:

The duration of the test as I have explained, is what it takes for the analyzer to arrive at a stable number. In the case of bar graphs that I post, that could be 5 to 10 seconds. In the sweeps, it is measured likely in 10s of milliseconds.

FTC requires that the amplifier survive 600 seconds at full power and full bandwidth.

(it seems like a really nice amp)

From looks, yes. But government doesn't accept that. It wants actual specifications which it lacks for both 1974 and today's regulation. The words "FTC" are not sufficient for the former. And for the latter, they simply have not run that test so statement is currently illegal.

 

[amirm]

I have an SX-1980 here, crated up and sent to me from 1500km+ away. Pioneer's TOTL, 1978, 270 watts per channel receiver. Go look up what that is worth and weep. It needs my attention to keep it happily going for another 46+ years...

It needed attention when it was new as well as I repaired a number of them back when it came out with blown amplification. There is a resurgence of getting these vintage products and that has driven the costs up. It has nothing to do with performance or reliability.

 

[amirm]

The FTC has made it easy for the industry with 1% THD for continuous tests. 1% is well into clipping. And if an amplifier doesn't clip due to it's design or protection? Test it at its rated continuous power for 5 minutes at any frequency you want, sine or square waves, with or without reactive loads.

I agree 1% THD was an OK move. I have already been using that for my power ratings. The problem as we have said repeatedly is the 5 minute rule.

Companies are not going to wake up and want to rate their amps at lower wattage. If they can change the protection circuit to allow the amp to cook more but pass the 5 minute test, they will. And with it, allow the amplifier to be damaged sooner.