somebodyelse
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It's disappointing that phone browsers can't do a decent job of rendering such basic HTML. You had one job...
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The FTC may consider dropping the Amplifier Rule.
- Thread starter 3dbinCanada
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Turns out it's only the Opera browser, the other browsers on my phone wotk fine. But I don't think I've ever found a single browser that works perfectly with all sites, I blame internet explorer.
My iPhone xs reads it easily, especially when I turn it horizontally. But you are right, I think my target readers do not preferably use cell phones to read the plots.
FWIW I almost never view a website on my phone. Too small, hard to see (constantly zooming in and out), and awkward to navigate. That's pretty much any website. Old fart.
somebodyelse
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Or sites that work perfectly in all browsers for that matter. The differences in browser behaviour certainly make life difficult for web developers. Safari seems to have taken over IE's job of holding developers back by not implementing current standards, but they all had their frustrations when I was dealing with such things.
Really? Tell me more. Does that explain why Safari gobbles up SO SO SO much of my MacBook Air's RAM?
As for the testing, I think for me there are a few things:
- How much power can the amp deliver without clipping for some medium length of time (one minute?). This is presuming a use case where you are cranking things up but not into heavy distortion continually.
- How well is the output voltage maintained into lower and lower impedance, and into NON-RESISTIVE impedance. As someone noted doubling power is often a fantasy wherein Marketing has under-rated the higher impedance. But I do think it is better, it is one of my audio superstitions that an amplifier which is a better voltage source will somehow sound better...which contradicts other audio beliefs of mine perhaps
- What is the raw noise performance? Will it hiss into a directional horn tweeter?
- Then how clean is it i.e. distortions with music (or multi-tone representations)?
To me the long-time continual testing is a nice way to see if Behringer and Crown and those cheapies really do what they say, especially considering they are PA amps which should be able to do that, but it is the mid-time power that's relevant for home at least to me.
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somebodyelse
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Back to the tests, it looks like it's reasonably easy to take a specified power output and verify it using the FTC method, but a lot more time consuming to find the correct FTC power output if the amp fails to meet that specification, as with the B100. Had the A07 been tested with a higher voltage PSU I suspect the same problem would have emerged given what I remember of @pma's previous findings. Any thoughts on the quickest way to find the number people should be putting in their specs?
FWIWFM, I am against "dumbing down" the test to a shorter time (or lower power). If the amp cannot sustain its full power rating for five minutes in still air, chances are it won't be happy playing loudly for a few hours at lower power watching a movie or listening to music. Heat is the biggest detriment to lifetime for most electronics so proper thermal management is critical IME/IMO.
somebodyelse
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Too far off topic - start a thread and tag me if you want to continue.
Sure. And we can see what we get. 5 minutes no more than 10W/4ohm? OK, why not. But the customers should know. Because it is totally unfair if one producer declares rated power at 100W/4R and never reaches it, and the other one passes it easily. It is an unfair competition. And do not want for me to go political, though I would like to!
This is spot on.
After reading a couple of @pma 's reviews it occurs to me that perhaps the more valuable test might not be 5 minutes at the rated power, but the one hour warm-up at 1/8 power. We may buy for the peaks, but those don't last for 5 minutes, yet I use the amp for hours at a time at much less than peak.
In your Topping review I felt like you should have said at what point it failed during the warm-up. And yet, does it matter whether it fails at 5 minutes or 59 minutes? My assumption is that you walked away to do something else during that 1 hour, not expecting it to actually fail, so you didn't know the duration?
To me this is pretty much a pass/fail test, warm-up or the five minute period. This is less about distortion or anything else and more about thermal design and product longevity. If THD is <1% or whatever after 1 hr at 1/8 power and 5 minutes at full power I'm happy, and if it fails either at some indeterminate point before the time limits expire that's all I need to know. Let the manufacturers do their own failure analysis, good or bad is all I need to know from this test as a consumer. I will add the one thing I would find interesting at the end of the test is the ambient and case temperature at the end to see just how close to the edge thermal management of the device achieves. Warm to the touch, hot, or too hot to touch would be enough resolution for me on that one.
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restorer-john
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restorer-john
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Perfect! What make & model? One of those things on my "want but don't need list"...
That's why it was chosen as a pre-conditioning in the FTC test, I would guess.
Correct. In the comments/discussion the Federal Trade Commission essentially bowed to manufacturers' request to change the pre-conditioning to 1/8 instead of 1/3. IIRC the primary reasons were:
(1) 1/3 was worst-case for class AB biased amps, but many modern amplifiers are D, G, or H, so that is no longer true; and,
(2) 1/8 is more representative of typical music and movies for an average power.
FWIWFM - Don
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It is often very interesting to read old Audio (and Stereo Review) reviews testing amplifiers and receivers. Those tests, at least for some period of time, would follow the FTC '74 protocol (one hour preconditioning at 1/3 of maximum power output). That was the torture test (which I have seen described as a 'best case worst case' scenario for a Class AB amplifier). "Veracity" or internet lore? I dunno.
source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1975-02.pdf pg. 22
At any rate, the components under test didn't always fare too well.
source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1976-12.pdf#search="amplifier preconditioning" Onkyo TX-4500 test
The "new interpretation of the FTC rule" in this case came bwtween Feb '75 and Dec. '76.
source: https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1977-08.pdf pg. 44 (h/k Citation 16/16A review)
source: https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1979-04.pdf pg 64 (Phase Linear 700 Series Two (!?!) review)
Interestingly, searching mid-70s issues of Stereo Review reveals a fair amount of back-and-forth between then-technical editor Larry Klein and representatives of the US FTC about the details of the latter's test protocol.
Old_School_Brad
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History seems to be repeating itself. What was once widely known has gradually been forgotten, only to be rediscovered or reinvented later. It's as if there’s a generational memory gap, where each new generation has to repeat the mistakes of the previous one in order to reach the same conclusions.View attachment 409759
It is often very interesting to read old Audio (and Stereo Review) reviews testing amplifiers and receivers. Those tests, at least for some period of time, would follow the FTC '74 protocol (one hour preconditioning at 1/3 of maximum power output). That was the torture test (which I have seen described as a 'best case worst case' scenario for a Class AB amplifier). "Veracity" or internet lore? I dunno.
View attachment 409750
source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1975-02.pdf pg. 22
At any rate, the components under test didn't always fare too well.
View attachment 409751
source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1976-12.pdf#search="amplifier preconditioning" Onkyo TX-4500 test
The "new interpretation of the FTC rule" in this case came bwtween Feb '75 and Dec. '76.
View attachment 409755
source: https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1977-08.pdf pg. 44 (h/k Citation 16/16A review)
View attachment 409758
source: https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1979-04.pdf pg 64 (Phase Linear 700 Series Two (!?!) review)
Interestingly, searching mid-70s issues of Stereo Review reveals a fair amount of back-and-forth between then-technical editor Larry Klein and representatives of the US FTC about the details of the latter's test protocol.
Strange, isn’t it?
