Amplifier Specs

Mordenmail - I don't think 20Hz-20kHz is "given" since full power at 20kHz is absolutely useless. For class D it could not be possibly specified for the reason I mentioned before (full power at 20kHz would damage output filter).

Average music power is only few percent of max power. No need to design class AB amplifiers for sustained max power - otherwise they would have same size heatsinks as class A amps. Maximum current available is what counts.

Why would a company like B&K provide amplifier specs that use "cheater" measurments like "150 watts @ 1 kHz into 8 ohms"?

I believe the answer is simply that they are conforming to Consumer Electronics Association standard CEA-490A, previewed here, which is the currently applicable, and apparently voluntary, standard for specifying audio power amplifier ratings. As you'll see in the sidebar on page 2 of this article, only the 1kHz ratings are called for.

I believe that the 20Hz-20kHz ratings that were legally mandated by the FTC in 1974 were revamped ca. 1998 and in effect superseded by the CEA spec.

Regards,
-- Al

Here is a link to the revised FTC regulation which "exempts sellers who make power output claims in media advertising from the requirement to disclose total rated harmonic distortion and the associated power bandwidth and impedance ratings."

It is actually 16CFR432 (Title 16, Part 432 of the Code of Federal Regulations), not 46CFR432 as referred to in the CEA document I linked to in my preceding post. The effectivity date is indicated as 60 days following publication in the Federal Register, which apparently was 12/22/2000 as indicated at the end of this text of the regulation.

BTW, the CEA was at that time a sector of the EIA, so Bob's comment was essentially correct.

Regards,
-- Al

Correction: The link in my previous post labelled "this text of the regulation" should have been http://edocket.access.gpo.gov/cfr_2009/janqtr/16cfr432.2.htm

Regards,
-- Al

A sincere thanks to everyone for the free education. Almarg, thank you for the links.