AUDIO NEWS--Views and comment on recent developments.
by LARRY KLEIN, technical Editor
Amplifier Power Ratings
MANY people in and out of the hi-fi Industry have not been aware that the questions about the Federal Trade Commission's 1974 Rule on power ratings of amplifiers had never been fully resolved. A continuing subject of controversy has been the "preconditioning'" section 3(c) of the Rule requiring an amplifier to he "warmed up" for test by being operated at one-third power for one hour. How ever. for complicated electronic reasons, many of the 100-watt-per channel and larger amplifiers are more likely to blow up or shut off (rather than warm up) as a result of sustained operation at one third power.
I won't go into the full technical details here I interested readers can get a free reprint of my November 1974 article on the subject by sending a stamped. self-addressed, long envelope to Stereo Review, Dept. EC. One Park Ave.. New York. N. Y. 10016), but to recap the problem in brief: the preconditioning requirement unrealistically places a stress on the amplifier in a way that has no relationship to how well or badly it would perform under home-use conditions. This would not have been important had it not been for the fact that to meet the FTC's unrealistic warm up preconditioning requirement. amplifiers would have to he designed to be larger, heavier, and more expensive-and with little or no benefit to the consumer.
In any case. this difficulty has kept the issue alive, and after a year of back-and-forth discussion. a "solution" has recently been arrived at. according to a letter sent to the Institute of High Fidelity's Technical Director Leonard Feldman (and carboned to me) by Carthon F. Aldhizer. Attorney for the FTC's Division of Special Statutes. I quote:
Staff has reviewed this entire matter of pre conditioning of the amplifier with qualified electronics experts in government and have concluded that the language of the Rule can not he interpreted to permit use of the tone burst method of preconditioning.
However, it is our opinion that use of the automatic recycling method. i.e., permitting a piece of equipment to recycle (thermally cut off or on) automatically until "on time" of one hour is accumulated, is not inconsistent with the language of 3 (c) and would therefore constitute compliance with the Rule. Where thermal build-up presents a problem at the point of 3(e) testing, tests may commence at, for example, 250 milliwatts to permit cooling. The above is a staff level opinion which is not necessarily binding on the Commission.
What does it mean'? First, some clarifications: The "tone-burst method of preconditioning" referred to was a suggestion made in Stereo Review's article of November 1974 (which see). The "automatic recycling method" that was found acceptable in the second paragraph was a suggestion I made to the FTC's William Dixon a year or so ago when the preconditioning hassle first started, but the idea was dropped when it turned out that several amplifiers. when they went into protective thermal turn-off, would not automatically return to operation when things cooled down but would require a manual reset of some sort. The idea has been revived because it presents an easy solution short of rewriting the Rule, and it is simple enough to redesign an amplifier to automatically reset after thermal shutdown. The 3(e) test referred to has to do with the actual measurement of full power for 5 minutes-which would be difficult to accomplish if the amplifier kept shutting down because of the "thermal build-up" during the preconditioning hour.
It looks, therefore, as if the forces of hi-fi reason, organized under the banner of the IHF. have prevailed. Even if the Rule as it now stands and is interpreted is not totally satisfactory from the point of view of the technical purist, it has already accomplished certain good things for the hi-fi consumer. Note that it has been at least a year now since you last saw advertised a S150 compact system that included a record player, an 8-track tape player. AM/FM stereo. a free pair of head phones. and 100 watts of "peak effective power." Thanks to the FTC. amplifier power ratings are finally honest and reasonably comparable.
Speaker Patent Upheld
THE Bose Corporation has asked us to publicize the fact that the trademarks and patents on their Model 901 speaker have been upheld in the U.S. District Court in New York after four years of litigation. The trade mark at issue was the physical appearance of the Model 901 and the patent aspect involved was the use of an equalizer with speaker systems incorporating a multiplicity of small loudspeakers.
Blessing the Pressing
URI GELLER, famed Israeli psychic, metal-bender, and general-purpose ESPer, has an album out on Columbia (KC 33481). According to the press release accompanying it, the album consists of Uri's "unique poetry and writings with musical accompaniment provided by the international concert pianist Byron Janis and well-known composer-arranger Del Newman." The record itself (or at least my copy of it) seems to be responsive to Uri's reputed control over the shape of physical objects: it is one of the few discs to come into my office almolutely unwarped! Since the warp problem. judging from reader mail, doesn't seem completely soluble by conventional means, perhaps a Uri Geller trained surrogate installed at each record-pressing plant might help--or it may be that a simple laying on of hands at the presses once a month by the master himself would suffice.
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Also see:
AUDIO BASICS--Glossary of Technical Terms-24
Source: Stereo Review (USA magazine)