More on the FTC Amplifier Rule (1974) 1 Hr Pre-conditioning & Mfr Model Numbers
A.P. Van Meter had told me (a number of years ago) about his phone calls he had with the FTC in an effort to meet the FTC 1/3rd power preconditioning spec.
He was regularly asked what Phase Linear was doing in an effort to meet it. One day he re-read the spec and the next time they called he stated that he re-read the spec and it said "cumulative". They never called him again. It may have been his greatest contribution to audio?
After I went home, I read the spec myself and couldn't find the word cumulative, accumulative or accumulated anywhere.
A.P. also told me that the FTC didn't like the model number to imply the power output of the amplifier. I didn't see that anywhere in the FTC spec either.
I had been searching for anything related to this for years and finally today I found some more information on the subject that confirms what A.P. told me.
DB Magazine January 1976 pg 40:
http://www.americanradiohistory.com/Archive-DB-Magazine/70s/DB-1976-01.pdf see page 40 (42 of 44 in pdf)
"An additional interpretation of the audio amplifier rule for the high fidelity industry has been incorporated in a letter addressed to Leonard Feldman, technical editor of the Institute of High Fidelity, and signed by Carthon E. Aldhizer of the division of special statutes, F.T.C. “… use of the automatic recycling methods, ie., 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 Regulation (3c) testing, 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” This section (3c) requires that amplifiers deliver one third of their rated power output for one hour before measurements are made to determine final publishable power ratings."
Billboard magazine October 26, 1974 page 50 (NOV.4 FTC DEADLINE) Audio Firms Must Back Up 'RMS'
https://books.google.com/books?id=s...EIQDAF#v=onepage&q=Aldhizer amplifier&f=false
“…Another practice by some manufacturers to name the wattage output after their own brand name (ie: 400 Smithphonic watts) in an effort to circumvent the rule has also been outlawed…..”
Years later the spec's (FTC, EIA etc) were relaxed to 1/8th power pre-conditioning for 1/2 hour.
There was also a review of the Phase Linear 700 series II amplifier in Stereo Review April 1979
on page 64:
"Laboratory Measurements. When we tested the original Phase Linear Model 700 about seven years ago, the FTC ruling on amplifier power ratings had not been issued. The ruling resulted in the "beefing up" of many high powered amplifiers, Phase Linear's included, to withstand the severe heating conditions imposed by the "preconditioning" operation at one-third power for one hour."
"The Model 700 Series Two specifically requires the cooling fan accessory for this type of testing. Even with it, the thermal-protection circuit cycled on and off regularly, with a duty cycle of five minutes on and 1-1/2 minutes off when we drove both channels to one-third power into 8 ohms. To accumulate the required one hour of operation, we had to run the amplifier for 1 hour and 20 minutes."
"At the end of that time, the amplifier was very hot. Nevertheless, it seemed to suffer no ill effects from this treatment. The outputs clipped at 473 watts per channel (IHF clipping headroom = 1.18dB) and the IHF dynamic-headroom rating of 1.48dB corresponded to a short-term output of 506 watts per channel into 8 ohms at the clipping point. We could not measure the amplifier with 4 ohm loads, since the 10-amp line fuse blew before we reached the clipping point."
Ed
A.P. Van Meter had told me (a number of years ago) about his phone calls he had with the FTC in an effort to meet the FTC 1/3rd power preconditioning spec.
He was regularly asked what Phase Linear was doing in an effort to meet it. One day he re-read the spec and the next time they called he stated that he re-read the spec and it said "cumulative". They never called him again. It may have been his greatest contribution to audio?
After I went home, I read the spec myself and couldn't find the word cumulative, accumulative or accumulated anywhere.
A.P. also told me that the FTC didn't like the model number to imply the power output of the amplifier. I didn't see that anywhere in the FTC spec either.
I had been searching for anything related to this for years and finally today I found some more information on the subject that confirms what A.P. told me.
DB Magazine January 1976 pg 40:
http://www.americanradiohistory.com/Archive-DB-Magazine/70s/DB-1976-01.pdf see page 40 (42 of 44 in pdf)
"An additional interpretation of the audio amplifier rule for the high fidelity industry has been incorporated in a letter addressed to Leonard Feldman, technical editor of the Institute of High Fidelity, and signed by Carthon E. Aldhizer of the division of special statutes, F.T.C. “… use of the automatic recycling methods, ie., 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 Regulation (3c) testing, 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” This section (3c) requires that amplifiers deliver one third of their rated power output for one hour before measurements are made to determine final publishable power ratings."
Billboard magazine October 26, 1974 page 50 (NOV.4 FTC DEADLINE) Audio Firms Must Back Up 'RMS'
https://books.google.com/books?id=s...EIQDAF#v=onepage&q=Aldhizer amplifier&f=false
“…Another practice by some manufacturers to name the wattage output after their own brand name (ie: 400 Smithphonic watts) in an effort to circumvent the rule has also been outlawed…..”
Years later the spec's (FTC, EIA etc) were relaxed to 1/8th power pre-conditioning for 1/2 hour.
There was also a review of the Phase Linear 700 series II amplifier in Stereo Review April 1979
on page 64:
"Laboratory Measurements. When we tested the original Phase Linear Model 700 about seven years ago, the FTC ruling on amplifier power ratings had not been issued. The ruling resulted in the "beefing up" of many high powered amplifiers, Phase Linear's included, to withstand the severe heating conditions imposed by the "preconditioning" operation at one-third power for one hour."
"The Model 700 Series Two specifically requires the cooling fan accessory for this type of testing. Even with it, the thermal-protection circuit cycled on and off regularly, with a duty cycle of five minutes on and 1-1/2 minutes off when we drove both channels to one-third power into 8 ohms. To accumulate the required one hour of operation, we had to run the amplifier for 1 hour and 20 minutes."
"At the end of that time, the amplifier was very hot. Nevertheless, it seemed to suffer no ill effects from this treatment. The outputs clipped at 473 watts per channel (IHF clipping headroom = 1.18dB) and the IHF dynamic-headroom rating of 1.48dB corresponded to a short-term output of 506 watts per channel into 8 ohms at the clipping point. We could not measure the amplifier with 4 ohm loads, since the 10-amp line fuse blew before we reached the clipping point."
Ed
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