FTC Seeks Public Comment on Amplifier Rule Amendments to Make Testing Methods More Useful to Consumers
Text of the Notice of Proposed Rulemaking Regarding the Amplifier Rule
"Rated power shall be obtainable at all frequencies within the rated power band of 20
Hz to 20 kHz without exceeding 0.1% of total harmonic distortion after input signals at said
frequencies have been continuously applied at full rated power for not less than five (5) minutes
at the amplifier's auxiliary input, or if not provided, at the phono input."
Continuous rated power for 5 minutes is going to be difficult for many audio amplifiers.
Full power at 20KHz may be useful for testing a smoke detector.
Text of the Notice of Proposed Rulemaking Regarding the Amplifier Rule
"Rated power shall be obtainable at all frequencies within the rated power band of 20
Hz to 20 kHz without exceeding 0.1% of total harmonic distortion after input signals at said
frequencies have been continuously applied at full rated power for not less than five (5) minutes
at the amplifier's auxiliary input, or if not provided, at the phono input."
Continuous rated power for 5 minutes is going to be difficult for many audio amplifiers.
Full power at 20KHz may be useful for testing a smoke detector.
Rules ... what rules.
There is no legislation as to how amplifiers are tested. The manufacturer tests as they see fit, save the fact they must notify what sort of rating; Peak music power (4xRMS), Music power (2xRMS) or RMS (actual power).
I must say you will have a very odd smoke detector if it is affected by noise. They detect smoke in the atmosphere by way of partiiculates that reflect light back to the detector within the light free cavity.
There is no legislation as to how amplifiers are tested. The manufacturer tests as they see fit, save the fact they must notify what sort of rating; Peak music power (4xRMS), Music power (2xRMS) or RMS (actual power).
I must say you will have a very odd smoke detector if it is affected by noise. They detect smoke in the atmosphere by way of partiiculates that reflect light back to the detector within the light free cavity.
I would expect that many "linear" amplifiers (class A/AB/B) would emit a cloud of smoke at 20KHz full power.
Think about it...
I for one would like to see this type of testing protocol, if only to see published all those '10kW' 4-channel 1U digital amps' real output at 20Hz! (Probably about 800W).
0.1% white noise? Impulse? Multitone?
Sine? Square? Triangle? Arbitrary?
Most amps should be able to do impulse testing at full power for 5 minutes without issues. White noise, er, well....
Sine? Square? Triangle? Arbitrary?
Most amps should be able to do impulse testing at full power for 5 minutes without issues. White noise, er, well....
Last edited:
ANY amplifier these days is going to have a problem with 5 minutes of full power. The only ones that could do it were the boat-anchor touring grade class H units (Like old Crest), but only if fed off a 50 amp circuit. They draw WAY more than 20 amps doing it. Older class ABs would overheat before 5 minutes were up, and modern class D (even the tour grade ones) will shut themselves off long before any 5 minutes. Consumer equipment - no way. Not enough heat sinking. A 90 pound block designed for 75% efficiency was the only thing that would get you within spitting distance of 5 minutes.
One would argue that 5 minutes at full power is never needed. But 5 SECONDS is. Most ANY consumer receiver (or linear AB, G, H) will do that. If it can’t it should be trashed. Most class D stuff can’t. It will shut down and get pissy - mostly because of limiting in the switch mode power supply. Especially those 10 KW 1U units - they back off to protect themselves and the speakers. I wish they‘d have a “5 second rule”, because anything that passes that would be trusted not to misbehave when cranked to 11.
Class A amps should survive easily 😉
Music Instrument amplifiers too.
Think rail to rail squarewave clipping , caused by 10 to 20dB signal overload, driving a crazy impedance Guitar or Bass speaker, often in a poorly designed or even open back cabinet , for eight hours (typical shared 8 band festival in a cheesy place) and we are talking.
Under that onslaught, not only power semiconductors, Fans in my amps first cool the Power Transformer , go figure.
Am I "exceptional" or something?
No way, that is the basic requirement for Live use in a Rock Festival situation.
Add PA and DJ power amps to the mix.
Think rail to rail squarewave clipping , caused by 10 to 20dB signal overload, driving a crazy impedance Guitar or Bass speaker, often in a poorly designed or even open back cabinet , for eight hours (typical shared 8 band festival in a cheesy place) and we are talking.
Under that onslaught, not only power semiconductors, Fans in my amps first cool the Power Transformer , go figure.
Am I "exceptional" or something?
No way, that is the basic requirement for Live use in a Rock Festival situation.
Add PA and DJ power amps to the mix.
The testing methodology seems arbitrary so maybe an arbitrary waveform is appropriate.
I think we can agree that any amplifier should be designed to work reliably considering its application.
For example, fans are often used in amplifiers designed for professional applications whereas they are not desired nor are they necessary for a home audio system.
The question is where to draw the line, especially for consumer use.
If a well designed amplifier used for 2 channel or home theater is "beefed up" adding size, weight, and cost just so it can deliver continuous full power, one could argue that there is no real world benefit to the consumer.
I'm not sure that many tweeters could survive 20KHz at continuous high power levels (>100W).