Testing amplifiers at 5W/1kHz and using such parameter as a comparative parameter is IMO probably the worst choice. Why? Below please check the example of a conventional small class AB amplifier and its THD vs. power plots where idle current of the output stage is the parameter. Covering several mA to about 300 mA. For low values of idle current, crossover distortion rises for smaller signal amplitudes. But at 5W, it is almost independent of the idle current. At least 3 points should be used for amp comparisons. Take it into account, @amirm !
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Why testing at 5W is probably the worst possible choice
- Thread starter pma
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Nope. Replot THD+N, not just THD.
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Depends on N of the DUT. Distortion in case of crossover distortion or quantization distortion (CD without dither) is audible even below noise level.
The example above was simulated, below is the measured one, but still at reasonable bias current. Millivolts are across 0R22 Re emitter resistor. More later.
The example above was simulated, below is the measured one, but still at reasonable bias current. Millivolts are across 0R22 Re emitter resistor. More later.
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Maybe, in 50's, Dr Harry F.Olsen of RCA made real sound level measurment of symphonic orchestra and determined that maximum power you need in a standard living room is 5w, mono. He didn't mention the efficiency of the speaker, but we assume to be less than 90db/1w/1m.
Sokel
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Judging by the horns here (15" coaxial), probably a lot more than 90dB/1W/1m:
Speakers of the era were basically horns and if we take into account that horns can go loud even without an amp (like the 1913 gramophone I have) , 5W are enormous to them.
I think the issue here is the context that the measurement is used in:
@pma is more of a designer/engineer type, where obviously the 5W only test isn't enough to define the full performance of the device
@amirm is a reviewer, and the premise is that the hard work was already done, and the device performs as optimally as it can be. Obviously, here a 5W measurement doesn't say all, but then again, it's not the only measurement that is done.
I guess, whatever power level you choose, you can find examples that would prove that it's not ideal.
@pma is more of a designer/engineer type, where obviously the 5W only test isn't enough to define the full performance of the device
@amirm is a reviewer, and the premise is that the hard work was already done, and the device performs as optimally as it can be. Obviously, here a 5W measurement doesn't say all, but then again, it's not the only measurement that is done.
I guess, whatever power level you choose, you can find examples that would prove that it's not ideal.
Wouldn't separate noise measurements indicate how well a PCB and components (Powersupply, main board etc.) are designed and assembled ? Besides obvious genuine quality components used and circuit design ofcourse.
If the tests does not take too long. Why not have both ?
If the tests does not take too long. Why not have both ?
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That implies about 20 percent electrical efficiency. The old rule of thumb is an orchestras acoustic power output is ca. 1 watt.
That level of efficiency is on the high side of typical of the kind of loudspeakers Olson (note spelling) was used to, but not outrageous. Modern loudspeakers are far less efficient at turning electrical power into acoustic power, and ask a lot more of amplifiers -- but, to their credit, I suppose, modern loudspeakers are smaller.
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Because they take too long.
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Amir already measures signal-to-noise ratio at 5 W and at full power.
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We've already had some chit-chat on the topic of meaningful assessment of power amplifier performance. 
www.audiosciencereview.com
Power amplifier tests with respect to FTC: 16 CFR Part 432 (July 5, 2024) requirements on output power claims
Some of us feel the need of honest specifications of amplifier output power according to acknowledged documents like FTC regulations and IEC standards. The reason is to get comparable data, protect potential customers and draw attention to false claims of some manufacturers. I have decided to...
www.audiosciencereview.com
The section you quoted was about at what sound level listening tests should be conducted. Nothing was said about amplifier power.
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Col. Paul Wilbur Klipsch (yeah... him ) famously quipped:
Although this particular bon mot (Klipschism, to the faithful) is a little harder than many to pin down, Klipsch probably had Brook's model 12A4 push-pull 2A3 amplifier in mind when (and if) he said it.
Some of Klipsch's one-liners are considerably better documented.
A personal favorite, dating back to April 1974, remains:
) famously quipped:Although this particular bon mot (Klipschism, to the faithful) is a little harder than many to pin down, Klipsch probably had Brook's model 12A4 push-pull 2A3 amplifier in mind when (and if) he said it.
Some of Klipsch's one-liners are considerably better documented.
A personal favorite, dating back to April 1974
, remains:source: https://assets.klipsch.com/files/Dope_740400_v14n1.pdf
I have read about the 5w more than 40 years ago, maybe in J. Hiraga publications.
It was measured at mid priced seat. I estimated at that time to get the same measured level with 5w amp, the speaker used was 90db.
Here for music in theater is 95db max.
Put your system at maximum comfortable level and with scope measure the peak level and convert it what it would be with 90db speaker.
In 60's to 70's, we had 2.5w by ECL82,amps, and hardly we could push to max in radios, tvs or turn tables without disturbing the neighborhood.
It was measured at mid priced seat. I estimated at that time to get the same measured level with 5w amp, the speaker used was 90db.
Here for music in theater is 95db max.
Put your system at maximum comfortable level and with scope measure the peak level and convert it what it would be with 90db speaker.
In 60's to 70's, we had 2.5w by ECL82,amps, and hardly we could push to max in radios, tvs or turn tables without disturbing the neighborhood.
Sound level measurements are averages (time weighted averages). Lmax is the highest time weighted sound level during the measurement period. For "slow" the time constant for the time weighted averaging is 1 s, and for fast the time constant is 0.125 s. Industrial noise measurement (for worker hearing health) is usually conducted using "slow" and A frequency weighting. Therefore, a "95 dB max" sound level (assuming it is Lmax) doesn't tell you what the absolute sound pressure peak (Lpeak) is. Since, for a high fidelity reproduction, the sound system (both amplifier and loudspeaker) will have to produce Lpeak with low distortion levels, they should be sized to produce Lpeak, not Lmax. And Lpeak can easily be >10 dB (= 10x power) higher than Lmax. See below.
Source: https://larsondavis.com/learn/sound-vibe-basics/sound-measurement-terminology
Also: https://community.sw.siemens.com/articles/en_US/Knowledge/Sound-Level-Calculations-LAeq-LAS-LAF-SEL
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