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Gainsetting, and other aspects of audio engineering in the mid 1960's

"When I recorded back in East Germany we used dual half track tape machines without Dolby. Gainriding was almost unavoidable for larger works, or you ended up overloading the tape on the crescendi (anything marked fff in the score), while anything pianissimo (ppp) would drown in tape noise."

This was done because the customers were idiots who couldn't hear distortion or compression but thought that tape hiss was bad. One can hear at least 15 dB into white noise with 20 kHz bandwidth and the musical dynamics are seldom more than about 50 dB (measured from the loudest part of the loudest note to the softest part of the quietest note that is still being played). There are still idiots who buy classical music from BIS and complain about excessive dynamics. These people can even be found on Audio Asylum. Their problems are a noisy environment, an unsuitable domestic arrangement, or an inadequate system. (Listening in a car would be a worst-case example.)

At my college radio station we were using full track 7.5 recording on a portable Ampex 600 for "remotes". From several nearby halls we had dedicated and equalized lines we ran through steam tunnels or rented from the phone company. This enabled us to use our rack-mounted full track Ampex 350 at 15 IPS. Later, we got a stereo Ampex 354 and it did not sound as good as the mono recorder. Tape hiss was never much of a problem with any of these machines.

Our FM station had a modulation warning that flashed at 95% modulation. Engineers were trained to be competent to set gain so that in any given classical work this light would flash no more than once in any given loud portion, but at least once in any given program. If this light flashed more then very infrequently we would risk being cited by the FCC for overmodulation, and hence the engineer would be forced to reduce gain. The senior engineers considered having to adjust gain during a broadcast or a recording to be an inexcusable error. (Of course the college seniors used these mistakes as an excuse to be a hard ass while training and evaluating freshmen for membership in the radio station. This was, to some extent a form of hazing. People who didn't learn the gain setting skills or couldn't learn to recognize and workaround all the usual forms of distorion washed out of the selection process.)

There were two skills involved in gain setting. First as to playing recordings one had to find the loudest part of the recording (e.g. look at record grooves) and play them off-line to find the required gain setting for suitable VU meter readings. As to live broadcasts, one had to attend rehearsals or do preliminary setups to get measurements and gain settings. This required some additional guess work, because musicians inevitably play a few dB louder in front of an audience, for whatever reasons. The second skill was a bit more esoteric. It concerned the relationship between the VU meter and the modulation warning device. The gain was fixed at the transmitter and the line amplifier sending the signal out of the studio had unity gain. The problem was that the VU meter measured an RMS average and the transmitter warning measured peak signal amplitude, and worse, signal amplitude after pre-emphasis (equalization).

Back in these days of mono FM broadcast, a few dB of signal to noise ratio at the customer's antenna gave essentially perfect FM reception because of the capture ratio. Later, when multiple 15 kHz channels were added to the 200 kHz allocated bandwidth there was less available quieting and fringe areas of poor reception were larger. This caused the economic motivation for FM stations to get louder. (AM stations always had this problem that louder modulation was better for coverage area.)

I broadcast the Boston Symphony Orchestra live out of Sanders Theater at Harvard University one time for the benefit of WGBH-FM. Their scheduled engineer was ill, so I was sent to the radio booth to turn on and check out the equipment. They told me not to touch the gain settings. They had already worked this out, taking into account the particular conductor and how much louder he played in front of an audience. Indeed, these settings were essentially perfect, within one dB of the maximum legal gain.

At my college radio station there was an ongoing war between the "techies" who repaired the equipment and the "controlmen" who ran the equipment. The usual practice was that the controlmen would complain (e.g. a bad LP cartridge) and the "techies" would say "sounds OK to me". On more than one occasion I found it necessary to physically break equipment that sounded OK to the techies, but sounded horrible to the engineers and producers. (I was an engineer and producer, and never a techie.) This was back in the mid 1960's, well before there was any "high end audio" with its "subjectivist vs. objectivist" split, but the split was already there, named or not.

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar


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  • Gainsetting, and other aspects of audio engineering in the mid 1960's - Tony Lauck 10/17/1511:53:23 10/17/15 (0)

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