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Executive Summary

 

In June of this year, the FTC revised the “Trade Regulation Rule Relating to Power Output Claims for Amplifiers Utilized in Home Entertainment Products.” Originally issued in 1974, the newly amended FTC Power Output Rating allows the consumer to more easily compare amplifiers today than the original rule did.

 

Required Parameters

 

An amplifier’s average power output must be expressed in watts-per-channel within the rated power band of 20 Hz to 20 kHz without exceeding 1.0% of total harmonic distortion plus noise (THD+N). This must be done at an impedance of 8 ohms after input signals have been continuously applied at full-rated power for not less than five minutes.

 

Minimum of Two Channels Driven

 

If the equipment is designed to amplify two or more channels simultaneously at a minimum, the left front and right front channels must both be driven.

 

Preconditioning

 

The amplifier shall be preconditioned by simultaneously operating all channels at one-eighth of the rated power output for one hour using a sinusoidal wave at a frequency of 1,000 Hz.

 

The disclosure of the rated power output must be clearly and conspicuously labeled “FTC Power Output Rating.”  

 

Any other power ratings given by a manufacturer must have a type size two-thirds the size of the FTC Power Output Rating and may not be in bold print. These would also be labeled “this rating was not tested under the FTC standard.”  

 

Other power ratings must be well-known and generally recognized by the industry. Any other disclosures that are made should neither intend nor pose the likelihood of deceiving or confusing consumers.

 

Historical Details

 

Before 1974, it was essentially the “Wild West” when it came to amplifier ratings. Companies could rate power output according to their chosen standard. An example is the LR524 amplifier sold by the large catalog electronics company Lafayette Radio. The quoted spec is “Music Power,” which is a short-term burst (approximately 10 msec) of a 1 kHz tone.  The short burst holds the power rails at the maximum voltage before the primary power supply capacitor starts to discharge. The impedance load is not specified, but I verified it as 4 ohms, which increases the power output over the typical 8-ohm load. Only a single channel is driven. The +/-1 dB indicates this is the power from a typical sample, not the worst-case sample in a production run. In reality, the actual power may be -1 dB lower or 80% of the specified power.

Above is a screen scrape of the catalog page 3.

 

www.worldradiohistory.com/Archive-Catalogs/Lafayette-Catalogs/Lafayette-1973.pdf

 

In 1974, the Federal Trade Commission had had enough of this and ordered that consumer audio power amps must be correctly specified to reflect real-world performance. The FTC required the power to be measured by a continuous average signal over the audio band and a realistic distortion level. Subsequently, in Lafayette’s 1975 catalog, the same LR524 amplifier was now specified as 5 Watts average per channel into 8 Ohms at 1% THD over a band of 40 Hz – 20 kHz.

Above is a screen scrape of the 1975 catalog on page 25.

https://www.worldradiohistory.com/Archive-Catalogs/Lafayette-Catalogs/Lafayette-1975-750.pdf

Knowledgeable consumers who subscribed to enthusiast magazines like Popular Electronics or Audio Magazine would not have been surprised by the result. The Lafayette LR524 was reviewed in January 1973 (pages 78-80) and July 1972 (pages 42-44), respectively. Indeed, measurements of 100s of these products in these magazines and others such as Electronics World, High Fidelity, and Stereo Review, among others, supplied evidence of the deep gulf between an accurate measurement of the amplifier’s actual power output and the advertised power.

The original 1974 FTC power rule, with comments from the drafters, can be viewed in photographs from the original 1974 Federal Register which has become brown with time:

https://archives.federalregister.gov/issue_slice/1974/5/3/15383-15394.pdf#page=5

Surprisingly, the original FTC Power Rule does not give a specific maximum value to be used for the THD in the approved measurement. The document also only mentions “manufacturer’s rated power band.” The industry itself appears to have moved to a THD spec of less than 1% and a minimum bandwidth of 40 Hz to 20 kHz, for the most entry-level products in the mid-70s. Some of those were not able to make it to 20 Hz.

Resulting Amplifier Design Changes.

Companies could not live with products suddenly having to be rated 3 to 6 times lower in actual power. The main reason for these lower actual power results was the small power supply primary regulator capacitor and the associated undersized power transformer. When driven for 5 minutes at 20 Hz, the supply rails would drop dramatically, so larger transformers and primary capacitors had to be used.

The other problem was that amplifiers of the time had capacitors between the amplifier’s output and the speaker terminal. These capacitors were too small, resulting in a drop in power at 20 Hz because a large part of the power amplifier’s voltage swing appeared across the output capacitor and not the speaker.

The output capacitor had to go. It was replaced by complementary power rails. For example, an amplifier might have had a single 60V supply for the power amp. Now, +/-30VDC was used. This was a costly change. The power transformer secondary must have a center tap. A full wave rectifier is needed, and two expensive primary regulator caps are required.

To keep the power amplifier output at 0V with no signal applied, a differential amplifier replaced a single transistor at the power amplifier’s input. The change to the differential pair also helped reduce distortion at 20 kHz, as did a change to complementary output stages (PNP and NPN).

FTC rules are reviewed every ten years with comments for changes. In 2000, the resulting revisions were bad for consumers.

In the early 1990s, the FTC began systematically reviewing its rules every ten years.

When the FTC does this it requests comments on the rule and any proposed changes. The only people who appear to know when the rule is being reviewed are those producing the products. The FTC does not cast a wide net to other stakeholders. This allows for mischief to occur with overly one-sided comments. In 2000 the rule was significantly weakened.

https://www.govinfo.gov/content/pkg/FR-2000-12-22/pdf/00-32392.pdf

“The Commission is amending the Rule to exempt from media advertising disclosure of an amplifier’s total rated harmonic distortion and the associated power bandwidth and impedance rating.”

It was a terrible mistake, as the FTC would later admit in the 2024 rule changes, but things were about to get darker before the dawn.

The 2020 revision proposal. One FTC board member asked for the rule to be removed.

In 2020, the FTC posted a once-a-decade request for comments on the amplifier power rule.

https://www.govinfo.gov/content/pkg/FR-2020-12-18/pdf/2020-27569.pdf

It looked like a standard call for comments, but Commissioner Christine S. Wilson’s confirming statement was ominous:

“I question whether the FTC’s continued engagement in this space is constructive. Does it remain helpful for the FTC to specify the precise testing conditions manufacturers must use, and how they must communicate power output? Are there standard-setting organizations better suited to this task”?

www.ftc.gov/system/files/documents/public_statements/1585038/p974222amplifierrulewilsonstatement.pdf

How the rule was saved with people’s power.

The amplifier rule could have disappeared if the request for comment had remained known only to industry personnel, but by luck, consumers found out what was going on. The request for comments was open for three months (December 18, 2020), and the cutoff date was February 16, 2020.

The first public mention (we’re aware of) occurred in AudioScience.com on January 11, 2021, inside a thread on a Hypex amplifier.

“We are in luck! FTC is considering revisions to the amplifier power output rating standard (16 CFR Part 432). They are soliciting public comments until February 16, 2021. The last revision was in 2000/2001. This is a once in 20 years opportunity”.

Few saw this but it was a start. I found it by accident when I needed to reference it for a review I was doing. I sent back a detailed comment but did little else. On February 2nd, 2021, another member of the SECRETS staff posted information about the rule review and the link for public comments on our own Facebook page and a few Facebook audio group pages. On February 8th and 9th, articles on the need for comments appeared in Audioholics and Stereophile. News spread to AVS Forum.

Audioholics Wayde Robson created a template with many of the key points to use when writing the FTC. The comment period would close on February 16. Despite the short period, consumers flooded the zone with comments.

The Commission listens to the people.

The FTC responded with a notice of proposed rulemaking in 2022. It was the absolute opposite of what Commissioner Christine S. Wilson expected:

“In response, the Commission received 550 unique comments, including comments from amplifier and speaker manufacturers, amplifier sellers and purchasers, along with engineers and journalists in the audio field. All but one commenter supported retaining the rule. Based on this near-universal support, the Commission concluded there was a continuing need for the Rule”.

One of those comments was mine which showed up in the text:

“commenter David Rich (548) noted, “online product literature is showing values up to twice the power,” compared to tests conducted under conditions that reflect normal consumer usage”.

“Consistent with these comments (a total of 550), the FTC staff found this problem was ubiquitous in the marketplace. Specifically, staff found dozens of examples of the same equipment advertised with significantly different power output (e.g., some sellers advertised a particular model with 45 watts output per channel, while others advertised the same model with 100 watts per channel.”

https://www.govinfo.gov/content/pkg/FR-2022-07-27/pdf/2022-16071.pdf

Many other commentators were also cited in the text or footnotes. The FTC staff proceeded to do their own research, as shown above when they came upon an observation they thought needed further investigation.

The FTC solution.

The Commission however did not see a return to the original rule as a solution:

“In the past, the Commission has attempted to rectify this problem by requiring sellers to disclose load impedance, rated power band or power frequency response, and Total Harmonic Distortion (THD).”

The problem the Commission sighted was:

“Given the technical nature of the disclosed terms and the complex calculations needed to convert the disclosure into apples-to-apples comparisons of power output claims, these disclosures are unlikely to prevent most consumers from being deceived.”

The solution was:

<The> “commission proposes amending the Amplifier Rule to simplify power output measurements by standardizing test parameters. Specifically, the commission proposes requiring the following standard testing parameters: load impedance of 8 ohms, a power band of 20 Hz to 20 kHz, and a THD limit of less than 0.1%.”

The Consumer Technology Association tries to reverse the changes, but the FTC refuses.

The Consumer Technology Association, which has often promoted changes to the FTC power rule in the past, strangely did not send a comment for the original 2020 proposal, but when they saw the 2022 proposed rule change, they sent a six-page document objecting to the changes.

https://downloads.regulations.gov/FTC-2022-0048-0008/attachment_1.pdf

The FTC was having none of it. In the document they issued in response to the comments they wrote:

“The Commission staff’s research indicates standardization is necessary to eliminate conflicting and confusing power output claims. CTA’s comments do not change this conclusion”

One point the CTA tried to emphasize was that products with internal amplifiers should not be subject to the rule at all.

On internal amplifiers, the CTA lost again.

“CTA contends power output information is irrelevant to consumers of integrated home audio equipment. In contrast, Commission staff easily found multiple instances of sellers advertising such equipment using power output claims, presumably because they believe consumers find power output information relevant to their purchasing decision”.

Going into the weeds. Details about the rule process most readers do not need to know.

Unfortunately, the FTC does not email all the commentators that they have a proposed rule up on the FTC website. I had no idea that this newly proposed rule existed even though I sent a comment for proposed changes to the Power Rule in 2020. Nine people did learn about the new document and sent comments.

Two comments pointed out that the 0.1% distortion specification was too strict, and many amplifiers (especially tube amplifiers) would not pass it. After the Commission reviewed some references on the audibility of distortion in audio electronics, they decided that 1% was likely not audible. Thus, the FTC moved the spec to 1%. Another comment pointed to using THD+N instead of THD. The commentor sighted the change would capture power supply noise. Finally, the FTC allowed testing with a THD+N measurement system with a band limit of 20 kHz. The FTC document concludes, based on its research, that harmonics past 20 kHz are not audible.

The Commission asked for comments on the revised rule from July to September 2022.

On August 21, 2023, the FTC published a modified rule in response to the nine commentators who somehow found out about the July 2022 version.

https://www.govinfo.gov/content/pkg/FR-2023-08-21/pdf/2023-16792.pdf

The FTC asked for final comments on the August 2023 document and got four.

Again, the CTA tried to squash it but had no luck.

https://downloads.regulations.gov/FTC-2023-0050-0003/attachment_1.pdf

The FTC did give the CTA a crumb.

“This rating was not tested under the FTC standard” rather than the proposed “This rating does not meet the FTC standard.” The use of this more neutral phrase should resolve CTA’s concern”

The final rule was issued in 2024.

https://www.govinfo.gov/content/pkg/FR-2024-06-12/pdf/2024-12744.pdf

As you can see from all the rule proposals and comment cycles, the government grinds slowly. The proposed elimination of the Amplifier Rule started in 2020. The final resolution and new Rule is dated June 12, 2024, and is in force as of August 2024.