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The FTC may consider dropping the Amplifier Rule.

@pma @restorer-john @amirm I've thought about this for a while (off and on). I would love for Amir to include it, but it puts him in a tight spot. The problem I see is that the products he reviews are not usually provided by manufacturers but rather consumer (member) owners, so a test that could potentially ruin an amp is risky. Yes, if the amp fails it's a "bad" amp, but if it happens then a consumer/ASR member is out what was a working amplifier. For a manufacturer-provided amp, I say have at it, but if provided by a member, at the least it would be appropriate to ask for the owner to agree to a test that might break his amp.

I do agree in setting the THD bar high for this test, like 1% or whatever, so PIM in the load resistors and connections is not a big deal and some big, cheap resistors can be used. I think the interest is mainly if the amplifier can actually meet (or just survive) full-power requirements for five minutes. But this still requires Amir build another load bank or two (4 ohm and 8 ohm? or just one bank with 4/8 ohm option), or perhaps someone could build and provide one to him?

The usual counter argument is that continuous full power is not a realistic requirement for actual listening, but if the spec is there I would like to see it tested. Certainly given @pma's recent test results, it is possible other amps are woefully short in meeting their own specs, let alone the FTC rule.

Random musings - Don
 
I think continuous full power, for just a few seconds, all channels driven, 20-20kHz, 8ohms, at some higher than normal distortion level would be fine. It would tell us enough.
 
DonH56 said:
The problem I see is that the products he reviews are not usually provided by manufacturers but rather consumer (member) owners, so a test that could potentially ruin an amp is risky. Yes, if the amp fails it's a "bad" amp, but if it happens then a consumer/ASR member is out what was a working amplifier.
Click to expand...

Don, I agree with you. On the other hand, there are many amps sent by the manufacturers. Topping is almost always the case.
This is a review and detailed measurements of the Topping B100 "monoblock" amplifier. It was sent to me by the company and costs US $299.
Click to expand...

So, there should be no obstacle for @amirm to test it properly. And the “power” of this amplifier is not so big to destroy any resistor load. It is also very easy to build the load. I use two 200W TE Connectivity resistors in parallel on the heatsink. I can measure distortion below -120 dB with them, so no problem. To me, the load is not the reason.

@davidc , we need to follow some standards. Otherwise, everyone has his own standards and own reasoning and it goes to nowhere.
 
pma said:
Don, I agree with you. On the other hand, there are many amps sent by the manufacturers. Topping is almost always the case.
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My fairly quick read of the threads has me leaning towards thinking it's a good 5 W amp, perfect for Klipsch. :) And yah we should test it all the way. That an amp measuring so great on most metrics fails so badly on this one is revealing.

pma said:
So, there should be no obstacle for @amirm to test it properly. And the “power” of this amplifier is not so big to destroy any resistor load. It is also very easy to build the load. I use two 200W TE Connectivity resistors in parallel on the heatsink. I can measure distortion below -120 dB with them, so no problem. To me, the load is not the reason.

@davidc , we need to follow some standards. Otherwise, everyone has his own standards and own reasoning and it goes to nowhere.
Click to expand...
I don't think the load's the issue, either, more resistance to hurting a member's amp, pushback on the need relative to real-life usage, and time. A full-power test at the end shouldn't take too much extra time? Let it run whilst collecting and saving the other data, then do a THD sweep at the end. The FTC has finally put in place a rule; be nice to follow it, and not dumb down the test.

I rarely measured power amps in my day job, not my area of design, but was around the test assemblies since some of my work was close to the front end. The power amp guys would run them with a thermistor attached that would shut the test down if the amp overheated. Something like that might help; if case temp reaches something like 85 C, the output devices are probably pushing 125 C or better unless thermal management is really good.

In any event, performing an official FTC full-power test is another check on bogus claims that ASR is all about exposing IMO.
 
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Thank you for your effort, PMA.

You wrote output noise level was measured with volume knob fully turned to the left, ie counterclockwise. That means at maximum attenuation. Is it true or is it an error and what you really meant was volume knob turned fully clockwise, fully to the right ?
 
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No, it is not an error. The pot is at the input, before the opamp. When measured turned full right, clockwise, and input shorted, the result is the same, as it must be. I agree it should be written the later way, to make it clear. But, then the input connector must be shorted, as the noise cannot be measured with open input.

If you count noise voltage from the 10W distortion graph, where S/N is measured by REW as 90dB, you again get something near 200uV, with respect to 6.3V (10W).
 
Fully accept that I don't really understand this.

Seems to me that this is a movement towards a more complete standard of Amp testing. Also seems to me that there are no other clear standards, universally recognised. I could easily be wrong about that.

This sounds like a very sensible way to go. This sounds necessary.
 
I think I posted this before here someplace, but not to this thread. Reflecting on the topic, it might be of some interest, historically and/or contextually.
Or not. :rolleyes: ;) :facepalm:

source:




 
@mhardy6647 , it is a nice document. Please note that in case of amplifiers like the one I posted a slightest difference in output power above the distortion knee (clipping) results in huge difference in distortion, so it would be close to impossible to distinguish 1% distortion power from 0.1% distortion power, both is in fact a malfunction. For vintage tube amplifiers, it definitely made sense.
 
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davidc said:
I think continuous full power, for just a few seconds, all channels driven, 20-20kHz, 8ohms, at some higher than normal distortion level would be fine. It would tell us enough.
Click to expand...
I think the test is equally focused on thermal performance as it is on the ability to deliver the stated power. The procedure requires a well-engineered thermal design.
 
The FTC test was, and still is, a torture test of sorts and indeed does require a lot of an amplifier to earn a high "RMS" ;) power rating.
There are certainly other, perhaps more "real-world" ways to assess power output (e.g., the Institute for High Fidelity's "Music Power" rating). The FTC test is, to its credit, pretty well defined (i.e., published power claims are testable).

In the current era, it seems to me that a test biased towards amplifier performance into low impedance loads would probably be a more helpful metric for judging the amp's ability to provide power to the current crop of commercial loudspeakers. There is a cadre of knuckle-dragging ;) audiophiles who insist on seeing an amplifier's power rating double down :rolleyes:-- i.e., if the amp is capable of producing x watts at specified THD levels from 20 to 20 kHz into an 8 ohm load, it had darned well better produce 2x watts at the same THD and bandwidth specs into a 4 ohm load! ;) But some of them actually realize that slightly under-rating the 8 ohm performance of an amp would allow this mighty feat to be marketed! :cool:

Then there's the issue - I think - that many people really don't understand that, say, 60 watts per channel doesn't really represent much of a performance increase relative to, say, 50 watts per channel. None of the standards really help, though!

All this being said (can you tell that I am still caffeinating this morning?), it's probably fair to say that less people than ever actually care about such things! They do care about being able to listen to whatever music (or space stations blowing up, or whatever) they want to listen to, on the loudspeakers they like (or, at least, the ones they have) at whatever volume level they choose (NIOSH guidance and neighbors notwithstanding! ;) ) with decent quality and bandwidth. I am not sure any numerical specifications really address those criteria, though.
 
mhardy6647 said:
The FTC test was, and still is, a torture test of sorts and indeed does require a lot of an amplifier to earn a high "RMS" ;) power rating.
Click to expand...
Well, I do not think so. Any amplifier I have deigned passes this test easily. It is rather a difference between a cheap consumer electronics goods and well designed gear with respect to reliability and worst case scenarios. And the FTC test helps to separate the wheat from the chaff. Most of the amps tested by Amir here are the toys, not the serious amplifiers. And that ridiculous 5W SINAD chart only supports the toy design. In case of Topping, I am sure that ASR is the marketing shop window. And the audience eats it happily. The readers lap up the chart leaders to immediately buy them and change them like socks. Sorry, such is the contemporary attitude of many people. Not everyone, I agree.
 
mhardy6647 said:
The FTC test was, and still is, a torture test of sorts and indeed does require a lot of an amplifier to earn a high "RMS" ;) power rating.
There are certainly other, perhaps more "real-world" ways to assess power output (e.g., the Institute for High Fidelity's "Music Power" rating). The FTC test is, to its credit, pretty well defined (i.e., published power claims are testable).

In the current era, it seems to me that a test biased towards amplifier performance into low impedance loads would probably be a more helpful metric for judging the amp's ability to provide power to the current crop of commercial loudspeakers. There is a cadre of knuckle-dragging ;) audiophiles who insist on seeing an amplifier's power rating double down :rolleyes:-- i.e., if the amp is capable of producing x watts at specified THD levels from 20 to 20 kHz into an 8 ohm load, it had darned well better produce 2x watts at the same THD and bandwidth specs into a 4 ohm load! ;) But some of them actually realize that slightly under-rating the 8 ohm performance of an amp would allow this mighty feat to be marketed! :cool:

Then there's the issue - I think - that many people really don't understand that, say, 60 watts per channel doesn't really represent much of a performance increase relative to, say, 50 watts per channel. None of the standards really help, though!

All this being said (can you tell that I am still caffeinating this morning?), it's probably fair to say that less people than ever actually care about such things! They do care about being able to listen to whatever music (or space stations blowing up, or whatever) they want to listen to, on the loudspeakers they like (or, at least, the ones they have) at whatever volume level they choose (NIOSH guidance and neighbors notwithstanding! ;) ) with decent quality and bandwidth. I am not sure any numerical specifications really address those criteria, though.
Click to expand...
I wouldn’t call it a torture test. Not long ago, manufacturers like Yamaha and Pioneer provided power ratings based on rigorous standards such as RMS, IHF, DIN, and IEC, all included in the same datasheet. While the trend has shifted and standards have declined over time, I don’t believe this justifies lowering expectations -yet that’s exactly what we risk doing when we label what was once the norm as torture tests.
 
I have just tested my Purifi 1ET400A EVAL2 mono amplifier. It has Hypex SMPS400A180 power supply (2x46V), so the maximum power is reduced to 180-200W/4ohm at THD%1%.

It was preconditioned at 25W/4ohm for one hour and at the end of preconditioning the amplifier case was cold without any increased temperature. It passed 5 minute 180W/4ohm/1kHz test with THD=0.62% and was only slightly warmer then. The resistor load was, however, very hot. Kudos to @Bruno Putzeys . This is the AMPLIFIER, not a toy.

My new review is here:

 
pma said:
Well, I do not think so. Any amplifier I have deigned passes this test easily. It is rather a difference between a cheap consumer electronics goods and well designed gear with respect to reliability and worst case scenarios. And the FTC test helps to separate the wheat from the chaff. Most of the amps tested by Amir here are the toys, not the serious amplifiers. And that ridiculous 5W SINAD chart only supports the toy design. In case of Topping, I am sure that ASR is the marketing shop window. And the audience eats it happily. The readers lap up the chart leaders to immediately buy them and change them like socks. Sorry, such is the contemporary attitude of many people. Not everyone, I agree.
Click to expand...
Is there any source of information that I can use to compare / choose amplifiers based on these 'better' tests?

My next amplifier is likely to be my last one - a power amp - I don't need SOTA but I would like it to be an amp that I never think about again. It'll probably never have to work hard, an easy life for it. Budget will not be unlimited, or high. I will change speakers but, again, I really doubt that they will ever be especially difficult loads.

The ASR reviews give me a way to compare amps and the forum itself is invaluable but, as I read more, I'm becoming more confused about the options ... I don't want a toy, I don't need fancy, I'd like *good*.

I'll get there, but I'm looking for a short cut :)
 
C
JeremyFife said:
Is there any source of information that I can use to compare / choose amplifiers based on these 'better' tests?

My next amplifier is likely to be my last one - a power amp - I don't need SOTA but I would like it to be an amp that I never think about again. It'll probably never have to work hard, an easy life for it. Budget will not be unlimited, or high. I will change speakers but, again, I really doubt that they will ever be especially difficult loads.

The ASR reviews give me a way to compare amps and the forum itself is invaluable but, as I read more, I'm becoming more confused about the options ... I don't want a toy, I don't need fancy, I'd like *good*.

I'll get there, but I'm looking for a short cut :)
Click to expand...
Considering FTC continuous test it seems that most of it is about thermal design.
You can have a look at the below links (they have examples too,it's not all math) and then make some simple calculations and eyeball what comes close in the market:


www.designworldonline.com

How to Select a Suitable Heat Sink

Laptop computer designers, audio amplifier makers, and power supply manufacturers can keep their products cooler by following these fundamental heat-sink
www.designworldonline.com www.designworldonline.com

An example for what it takes for 1/8th and 1/3rd of power:

Ex.PNG
 
Sokel said:
C

Considering FTC continuous test it seems that most of it is about thermal design.
You can have a look at the below links (they have examples too,it's not all math) and then make some simple calculations and eyeball what comes close in the market:


www.designworldonline.com

How to Select a Suitable Heat Sink

Laptop computer designers, audio amplifier makers, and power supply manufacturers can keep their products cooler by following these fundamental heat-sink
www.designworldonline.com www.designworldonline.com

An example for what it takes for 1/8th and 1/3rd of power:

View attachment 409462
Click to expand...
Thank you, that's interesting - I'll never be bored with this hobby - and sometimes I can even listen to music :)
 
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