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

As I have mentioned, whatever I use needs to be readily available to others to replicate the test conditions. I know how to do that with an array of high power resistors. Using your load complicates matters there unless you want to get in the business of producing commercial versions of it.
The Gerbers, BOM and CPL are available at https://github.com/mattclarkdotnet/dummyload. Literally load them up at JLCPCB and be done.

The STL for the case I need to extract from my son, so give me a minute or two - I'll put it in the same git repo.

For the fans, any 140mm case fans will do.

If you want more control (temp sense etc), then go for it. My attempt using an Pi Pico is here: https://github.com/mattclarkdotnet/ds1822_monitor
 
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Arcol HS200 4R7/200W resistor on heatsink, as below.

View attachment 417158

5 minutes test at 150W resistor power.

Initial values: Temp = 24°C (resistor body), R = 4.6 ohm
Final values: Temp = 85°C (resistor body), R = 4.3 ohm
Tempco = 0.005 ohm/°C. No fan used.

I just verified one of my test loads using no name Amazon.com 200W resistors. 8ohm//8ohm, 5 minute test, temp rising from 21°C to 100°C. Temperature coefficient turned out to be 0.001Ohm/°C.

Dissipated power with constant 30,4V voltage drifted from 226,69W at 21°C to 227,45W at 100°C. That's more than accurate enough for this purpose I believe.

20241229_145403.jpg

Note this load is not that large. It handled a 226W/5min test while it can only take 50W continously.
 
@Geert Looks good. I think we always find soluntion in case we really want to find it. Not trying to find excuses or silly suggestions like heater spiral. Appropriate load can almost always be made from combination of similar resistors.
 
I just verified one of my test loads using no name Amazon.com 200W resistors. 8ohm//8ohm, 5 minute test, temp rising from 21°C to 100°C. Temperature coefficient turned out to be 0.001Ohm/°C.

Dissipated power with constant 30,4V voltage drifted from 226,69W at 21°C to 227,45W at 100°C. That's more than accurate enough for this purpose I believe.

View attachment 417384

Note this load is not that large. It handled a 226W/5min test while it can only take 50W continously.
Not surprising. It’s a quality resistor, not a PTC.

Just imagine how chaotic the world would be if resistors regularly drifted 25% out of spec. because of a relatively small temperature change. :)

Amir has chosen not to change his testing procedures. He’s just not stating it directly, and that’s okay; it’s his decision.
 
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I don't know why I am bothering to answer....

You surprised me from the time you responded to those silly things.:D:D

A short in an amplifier can vaporize and set load resistors on fire in a blink of an eye.


Be careful, someone may take such YT jokes, or semi jokes serious!

Anyway, I have an idea, why not start testing with an inductor for current, in addition using resistors for voltage capability, it will cost more but it would not have those high heat dissipation issue. One of the option I took in U was power systems and one of my project was to test the effectiveness of using a short circuit coupler. In those early days, those things were actually used extensively, to limit the otherwise damaging current resulted from short circuits in the high voltage transmission and distribution systems. Even with the advance in protective schemes based on electronic processors/relays, short circuit couplers still would help in limiting short circuit currents with those advanced relaying schemes, I would imagine...

For amp output tests, it would be necessary to modify the concept, such as by using resistor of low values, may be 0.5 ohm or lower and it can be adjustable. It should be easy enough to calculate the values of resistance and inductance to limit the maximum current at the target voltage of say 80 V. 60 V, 2 ohm would be 30 A, if the resistance is 0.5 ohm then the dissipation is only 450 W, that would be practical enough to deal in a home lab. Using such an reactive load would kill two birds, one being the much concerned amp's ability to drive reactive loads, and the other is the even more questioned on forums about amp's high current capability. Such tests are already being done obviously, probably by you as you have done quite a few reactive load tests.

I used the term short circuit coupler simply borrowing the term from HV utility systems, to emphasize the possible use of an inductive load that would allow for such reactive load tests done at much higher current, with much less heat to deal with if resistors are use.
 
I can't use stuff like that. My tests need to be repeatable. And fixture usable indoor with no risk of fire in the case of overload or amplifier shorting.

I didn't at all mean to infer you could use the water heater elements.

I meant to be providing the community at large with another example of a cost effective DIY dummy load. One that has a rather unique property of being able to make measurements affordable of very high power amps.

I mentioned that the water heater elements get very hot fast...that was to stress that they must be submersed in water.
When the elements are in a water reservoir of sufficient size, I think the rig has zero chance of fire risk.
I find the 5 gallon bucket setup entirely usable indoors. Easy to set up and dismantle...and most importantly, safe.

Like said, the resistance of the elements remains quite stable, or at least remained so for any test I ran, say 5 min max.

The highest power amp I remember testing was 4,000W EIA into 4 ohm. Which i get raises a 5 gal bucket of water about 1 degree C every 15 sec.
So a 5 min test at full power, if such were even possible on a 110V supply LOL, would raise starting room-temp water to only mid 100's F.

I've been very pleased with the rig's repeatability....and can highly recommend it for any DIY amp testers interested mainly in big picture measurements.. ..fwiw
 
Amir has chosen not to change his testing procedures.
I have repeatedly told you that I have been working on stress tests of amplifiers prior to discussion getting created. And that i recently added my full bandwidth, "FTC like" power testing:

index.php

I have and continue to make changes to my testing as I can justify and implement them. The discussion we have been having around dummy load is motivated by me examining options for loads that can handle large amount of power for certain duration.

What I have said clearly and repeatedly is that I am not going to adopt FTC regulation. Don't conflate the two. No amount of debating tactic as you are using is going to persuade me to do what is wrong for both users and manufacturers.
 
I mentioned that the water heater elements get very hot fast...that was to stress that they must be submersed in water.
Understood. Everyone I know who has built such loads does the same or use oil, etc. As I think you know, if I do something, I do it to highest levels of execution as there be no doubt about efficacy of testing. And my lab being a loft in our house, I have to make sure there is no risk of damage to the house with spilled water, nor electrical shock due to high voltages involved. Truth to be told, I almost set the lab on fire once testing AC power filters. Thankfully my heavy duty powerstrip had a breaker and it opened before the short got really out of hand!
 
Understood. Everyone I know who has built such loads does the same or use oil, etc. As I think you know, if I do something, I do it to highest levels of execution as there be no doubt about efficacy of testing. And my lab being a loft in our house, I have to make sure there is no risk of damage to the house with spilled water, nor electrical shock due to high voltages involved. Truth to be told, I almost set the lab on fire once testing AC power filters. Thankfully my heavy duty powerstrip had a breaker and it opened before the short got really out of hand!
I will chime in on this one. I used 250W4R Dale load resisters for many years as my loads. They ultimately where mounted on a heavy large SoundStream car amp heatsink. When the loads where not mounted on the heatsink I changed/burned the color of 3/4" plywood to a light brown color and the smell of browned wood permeated the air. Even after mounting them I was able to cause/burn in very slight fin marks underneath the car audio heatsink on a wooden workbench. A very high powered car amp can roast a load resister as well as a big behemoth home audio amp. So watch your solder joints, be careful with your loads and make sure you don't burn something or start a fire.
 
I have repeatedly told you that I have been working on stress tests of amplifiers prior to discussion getting created. And that i recently added my full bandwidth, "FTC like" power testing:


I have and continue to make changes to my testing as I can justify and implement them. The discussion we have been having around dummy load is motivated by me examining options for loads that can handle large amount of power for certain duration.

What I have said clearly and repeatedly is that I am not going to adopt FTC regulation. Don't conflate the two. No amount of debating tactic as you are using is going to persuade me to do what is wrong for both users and manufacturers.

Yes, you've mentioned that before.
It's easy to get the impression that, given your objections to most of the proposals, you might be looking for reasons not to make any changes in the end. For instance, in the recent discussion about loads, it turns out you already have two quality resistor loads.
If that's the case, why not run the continuous tests with those and monitor the temperature? I doubt many of the amplifiers you test will damage the resistors. And if they do get hotter than you'd prefer, you can simply add ventilation.

I'm not using any "debating tactic." I’m trying to phrase my posts carefully to ensure they're as polite as possible while still expressing my opinion, so as not to upset you further, which you already seem to be for some reason. -I guess you can call that a tactic if you really want to..

As for the FTC, it isn’t inherently wrong for both users and manufacturers. That’s just your opinion, and I, for one, think you’re mistaken. And no, this doesn't mean that I think it's perfect.
 
Understood. Everyone I know who has built such loads does the same or use oil, etc. As I think you know, if I do something, I do it to highest levels of execution as there be no doubt about efficacy of testing. And my lab being a loft in our house, I have to make sure there is no risk of damage to the house with spilled water, nor electrical shock due to high voltages involved. Truth to be told, I almost set the lab on fire once testing AC power filters. Thankfully my heavy duty powerstrip had a breaker and it opened before the short got really out of hand!

You should strongly consider installing a separate electrical cabinet for the test facility. This would allow you to use variable industrial overcurrent and circuit breakers that can trip much faster than those in your main cabinet.

They’re more affordable than you might expect.
 
Looking for something else (not unrelated, but OT for this particular thread) and apropos of nothing, a few historical power snippets (not scientifically curated!) from the pages of Audio.

1736181214020.png

source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1971-07.pdf

1736181342801.png

source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/60s/Audio-1960-Dec.pdf pg46ff

last and probably least ;) (although it does obliquely mention a famous if perhaps ill-documented Richard Burwen anecdata on perhaps unintuitive short-term power requirements for mundane audio reproduction task). Note that this is snipped (pun fully intended) from a full-page ad advertising a Carver amplifier ;) :
1736181483264.png


source: https://www.worldradiohistory.com/h...o-IDX/IDX/80s/Audio-1985-10-OCR-Page-0048.pdf

N.B. All offered strictly as-is and FWIW. No warranty express(ed) or implied.

PS I may have to incorporate electronic gagging into my vocabulary. :)
 
Yes, you've mentioned that before.
It's easy to get the impression that, given your objections to most of the proposals, you might be looking for reasons not to make any changes in the end. For instance, in the recent discussion about loads, it turns out you already have two quality resistor loads.
If that's the case, why not run the continuous tests with those and monitor the temperature? I doubt many of the amplifiers you test will damage the resistors. And if they do get hotter than you'd prefer, you can simply add ventilation.

I'm not using any "debating tactic." I’m trying to phrase my posts carefully to ensure they're as polite as possible while still expressing my opinion, so as not to upset you further, which you already seem to be for some reason. -I guess you can call that a tactic if you really want to..

As for the FTC, it isn’t inherently wrong for both users and manufacturers. That’s just your opinion, and I, for one, think you’re mistaken. And no, this doesn't mean that I think it's perfect.

I have found all of your comments in this thread polite and civil.

At the same time, I can certainly see why @amirm (not to mention others) would be frustrated and could reasonably refer to your approach as a "debating tactic" even if that is not your intention and you don't see it that way.

Two examples from your most recent comment:

1. You write in response to Amir, "It's easy to get the impression that, given your objections to most of the proposals, you might be looking for reasons not to make any changes in the end." Yet in the comment of Amir's that you wrote this response to, he explicitly states, "I have repeatedly told you that I have been working on stress tests of amplifiers prior to discussion getting created. And that i recently added my full bandwidth, 'FTC like' power testing" ... "I have and continue to make changes to my testing as I can justify and implement them. The discussion we have been having around dummy load is motivated by me examining options for loads that can handle large amount of power for certain duration."

"I have been working on" - "I recently added" - I have and continue to make changes" - "The discussion we have been having... is motivated by me examining options" - with respect, it is not plausible to read all of those statements of Amir's and respond that it seems like he's "looking for reasons not to make any changes."

For all I know, you might be trying to retrospectively justify your suspicion that he's not going to make changes - in other words, your intent might have been along the lines of, "Well, okay, now I understand, but in fairness until you made your last comment it did seem like you weren't really considering any changes." But that is most certainly not what you wrote. So to Amir your comment likely reads like a slap in the face, because your response ignores or dismisses pretty much everything he just wrote.

2. You end your comment by noting that Amir's negative view about 2024 FTC is "just [his] opinion," and that you think he's mistaken.

But throughout this entire thread you still have not provided any evidence or compelling reasoning for why 2024 FTC is even a feasible standard to try to implement, let alone a desirable one. And every time anyone has raised an objection to what appears to be an implicit reason you continue to argue in favor of 2024 FTC, you simply respond that they are mistaken about your reason, or you "did not say that" - and then follow up with a vague statement to the effect that "standards are important," which of course is a statement that no one disagrees with and that does not provide any argumentative support for 2024 FTC given that it is too vague and impractical to be implemented in a standardized manner anyway.

Now, I'm fairly confident that if you respond to this comment, much of your response will consist of some version of claiming that I have mischaracterized your view or statements, and/or that you simply disagree. That's your prerogative of course, but in that scenario you would simply be doubling down on the same approach that led Amir to make his comment.
 
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Agreed, Amir has implemented many changes in the last few years that I have been a member, and to be fair, I am not aware of other bench test sites such as HFHF, Stereophile or any other sites (except for Gene, Audioholics.com, who also tend to be receptive to suggestions, and implemented changes that made technical sense, though he has done far fewer bench tests on AVPs and AVRs than ASR that has done so many bench tests on audio gear including AVPs and AVRs, let alone integrated and power amplifiers.
 
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Agreed, Amir has implemented many changes in the last few years that I have been a member, and to be fair, I am not aware of other bench test sites such as HFHF, Stereophile or any other sites (except for Gene, Audioholics.com, who also tend to be receptive to suggestions, and implemented changes that made technical sense, though he has done far fewer bench tests on AVPs and AVRs than ASR that has done so many bench tests on audio gear including AVPs and AVRs, let alone integrated and power amplifiers.
Yes, Amir has made changes. For instance, I was excited when he introduced testing with reactive loads, though it became evident that this approach doesn’t work well for many smaller amplifiers.

ASR is occasionally credited with holding manufacturers accountable and even influencing changes in their practices. However, if third-party testers don’t evaluate products according to the same standards manufacturers are required to follow, how can they effectively ensure accountability for the claims being made?

For me, it was an eye-opener to learn that Amir’s power tests are conducted over an unspecified duration, typically estimated to be between 2-5 seconds.
 
However, if third-party testers don’t evaluate products according to the same standards manufacturers are required to follow, how can they effectively ensure accountability for the claims being made?
What manufacturers are following the new requirements? I know of one but you wouldn't like they way they're doing it.
 
Here we go again with FTC tests in long term max power output...

This is as relevant as testing a car engine running 10.000 RPM for how long until it overheats and breaks: an useless test for an unpractical real use case. Yet the FTC specifies such test for some clueless reason, and even worst, some people insist on it... :facepalm:
None of my cars (or trucks or boat motors) have ever blown up running them at either max rated RPM or Max power for 5 minutes on a chassis Dyno (or more) or in a boat: the boat motors will be propped to be able to run at maximum rated power RPM for 60 miles or more (for off shore fishing or just running around, maybe camping in the boat somewhere) on the water & do it time after time for many years while tuning them.
Not the ones with stock internals nor the ones that I have built to be able to turn more RPM.
Yes, some of us do test our gear, literally. Because we want it to blow up while testing it, so that we can fix the issue, so that it hopefully won't blow up while we are operating it.

Yes, my stuff gets tested: AMP, while this is not the 5 minute FCC test:
one of mine here:

NAD 2200 Vintage Amplifier Review

And a different one here:
#AmpDyno #AmpTest #NADThe 1987 NAD 2200 has some impressive specs. This vintage 2 channel audio amplifier is said to deliver up to 1600 watts bridged at 4 ohms dynamically. Quite an incredible feat for a 100w/ch 8 ohm rated amplifier. Is it possible this 30 plus year old amp can post these kinds of numbers? Or does it show it's age and let out the magic smoke? Only one way to find out... (and a surprise 2 ohm test)

 
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None of my cars (or trucks or boat motors) have ever blown up running them at either max rated RPM or Max power for 5 minutes on a chassis Dyno (or in a boat [the boat motors will be propped to be able to run at maximum rated power RPM for 60 miles or more on the water & do it time after time for many years]) while tuning them.
Not the ones with stock internals nor the ones that I have built to be able to turn more RPM.
Car and truck engines have mixed results when used in aviation and marine applications. Most were never designed to produce their max rated power continuously. The typical car engine uses only about 1/4 of its rated power continuously when cruising down the freeway and its full rated power only for brief moments. Most car engines don't last when installed in boats & airplanes that continuously demand 70% or more of rated power. Even when driven at SCCA and similar racing events, many of these engines get heat soaked and lose power or go into "limp mode" if operated at full power in low gears for more than a few minutes. A few car engines have worked well in marine & aviation applications; they are either modified or comprise the over-engineered exceptions that prove the contrary rule. For each one, there are many others that don't.

This analogy to engines is not ideal because of the term "continuous". Most car engines will produce their rated power (for example on a dyno) when properly maintained - yet are not certified or advertised to produce that max rated power continuously. Yet when it comes to audio amplifiers, the term "continuous power" is used, even if the amp shuts down or melts while producing that power. It's understandable if that is misleading.
 
Car and truck engines have mixed results when used in aviation and marine applications. Most were never designed to produce their max rated power continuously. The typical car engine uses only about 1/4 of its rated power continuously when cruising down the freeway and its full rated power only for brief moments. Most car engines don't last when installed in boats & airplanes that continuously demand 70% or more of rated power. Even when driven at SCCA and similar racing events, many of these engines get heat soaked and lose power or go into "limp mode" if operated at full power in low gears for more than a few minutes. A few car engines have worked well in marine & aviation applications; they are either modified or comprise the over-engineered exceptions that prove the contrary rule. For each one, there are many others that don't.

This analogy to engines is not ideal because of the term "continuous". Most car engines will produce their rated power (for example on a dyno) when properly maintained - yet are not certified or advertised to produce that max rated power continuously. Yet when it comes to audio amplifiers, the term "continuous power" is used, even if the amp shuts down or melts while producing that power. It's understandable if that is misleading.
No car analogy is perfect, but I understand why it’s often used -it’s something almost everyone can relate to. And you’re absolutely right; I agree with you that “continuous” should mean exactly what the word implies and represents.
 
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