"Phasing" in Tape Recording (Dec. 1973)

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by Herman Burstein

IN THE JULY 1973 issue of the Tape Guide, Michael Caponera asked how he could achieve what he called: ". . . a special effect. It is a whirling, swishing sound that affects the total sound.... The sound seems to rise, dip, and then 'null out' and start all over again. I have heard this called ‘re-phasing' and `phasing out.' How is this sound produced?" Since then a number of readers have most helpfully written in to suggest how one can achieve "phasing." From the volume of such letters, it appears that "phasing" is of interest to a considerable number of persons. Following, therefore, are excerpts from several representative letters. Those who have taken the trouble to write but are not quoted here will, I trust, accept my thanks nevertheless.

Mr. David Josephson, ARE P.O. Box 191, Middletown, Calif. 95461 writes: "Here is how it's done, with home equipment. Take three tape machines. Put the master tape on one machine and make simultaneous dubs onto the other two machines. Keep the dubs made on a particular machine on that machine. Now cue up the two dubs on their machines and start both machines at exactly the same time, with the outputs connected to left and right channels of a stereo amp (machine A's L&R outputs to L of amp; machine B's L&R outputs to R of amp). Now to produce the phasing, you must slow down one machine for an instant, then return it to normal speed, then slow down the other machine, and keep rocking back and forth. Some machines have variable speed controls, but I have found that pinching the capstan works better. The output of the stereo amp is then fed back into the third tape machine for a final dub (or the amp can be left out altogether). Basically you have two audio signals, equal in amplitude but differing in phase by a continuously variable amount. This procedure can also be used to make some very weird sounding echo effects." Mr. W. Lloyd Piper, 5628 Walnut St., Mentor, Ohio 44060 writes: "I have achieved this effect with a stereo tape deck and a variable speed turntable.

The information is first recorded on one track of the tape. After careful cueing, the music is then recorded on another track; with practice, one can speed up and slow down the turntable while recording this second track. The new track is alternately ahead of and then behind the undoctored track. When the two tracks are played back monophonically (that is, both tracks combined), the "phasing" effect can be heard. When this is done in stereo, the music moves from channel to channel, demonstrating the brain's ability to localize a sound source, based on small time differences between left and right ears.... The most difficult feat is to insure that music from both the tape (undoctored) and from the disc start simultaneously when one is making the recording of the second track at varying speed." Mr. Jim Dever, 82 Fairfield Avenue, Erie, Penn. 16509 writes: "The heterodyne effect is accomplished by combining two identical sound sources, such as a recording, slightly out of sync.

The heterodyne effect can be achieved in stereo, with the use of a stereo mixer, but for beginning experimentation, it is best to start with a mono effort. One track is recorded on one track of a stereo tape machine with the stereo amplifier in the mono mode. This track is then played back while recording the identical record on another track, using your finger to speed the record or slow it, and consequently take the record in and out of sync with the previously recorded material on the first track.

Professional engineers use variable-speed tape transports to achieve the same effect." Mr. Dever adds, "This effect produces a jet plane-like sound which professional recording engineers have employed on some popular recordings in recent years. Perhaps the most noticed of these was the 1960 hit The Big Hurt by Toni Fisher." Mr. Dan Thibault, Lafayette Radio, Syracuse West, N.Y. writes that an effective way to achieve "phasing" is as follows: "Take the left tape recording output of your amplifier and 'Y' it into the left inputs of two separate tape decks. Do the same for the right channel, feeding it into the right inputs of these two decks. Now 'Y' the line outputs of the decks together, left to left, right to right, and feed these to the line inputs of a third deck, for dubbing and catching the effect on tape. Listen to the output of the third deck via tape monitor. On the first two decks, input levels should be as closely matched as possible, for maximum effect. By touching the capstans of the machines gently, first one, then the other, you can regulate the rate or intensity of the effect. Borrow a couple of decks and try it the way the studios do it! You will blow nothing but your mind." Mr. Thibault notes further that .. the Maestro Corporation markets a `phase shifter' which produces almost the same effect. It has three rocker switches that can be combined for different speeds. It is primarily intended for live performances, but works great on tape, too." Mr. Fred Goldberg, 120-172 Alcott Place, Bronx, N.Y. 10475 informs us that the reader interested in "phasing" should look into the Surf Synthesizer, #3711K, which is in the catalog of PAIA Electronics Inc., P.O. Box 14359, Oklahoma City, Ok. 73114. Mr. L. G. Newton, President of Tempo Audio Industries Limited, 2 Thorncliffe Park Drive, Toronto, Ontario, Canada 354, states that phasing equipment is made by "Eventide Clockworks in New York . . . and by Carl Countryman Associates in Palo Alto, California." A brochure by Countryman contains, in part, the following information: "The Countryman Associates Phase Shifters are all-electronic time delay devices, useful for creating special effects on audio signals.... The phase cancellation effect called real flanging is often obtained by recording the same audio signal on two pieces of tape, which are then played back simultaneously on two tape recorders. The outputs of these recorders are combined at equal levels in a mixer or audio console.... The speed of one tape recorder is then varied by dragging one's hand on the supply reel flange in order to slow it down (hence the term 'reel flanging'). As the time delay of one relative to the other increases, some frequencies in the signal from one recorder will become exactly out of phase with the corresponding frequencies from the other recorder, and will cancel out in the mixer. The subjective effect produced is a sort of audio ‘turning inside out' as was used in The Big Hurt and Itchycoopark. A slightly different effect can be achieved by reversing the phase of one signal using an inverting amplifier or a phase inverting patch cord. The same effects can be produced using the variable time delay of a Countryman Associates Phase Shifter.... Reel flanging effects can be added to a signal without completely cancelling any frequencies by feeding the delayed output from a phase shifter back into its input in or out of phase at an appropriate level ... the amount of phase cancellation can be controlled by varying the level of the feedback signal, producing more melodic effects than normal reel flanging." Based on the foregoing, it appears that, using one, two, or three tape machines, plus care and ingenuity, the experimental tape recordist can carve out a new dimension for himself.

Use of one machine would involve a phono disc as the source, so that the same source could be used first to record one track and then, at variable speed, a second track. If a tape is to be the source, then a minimum of two machines is required. Using either one or two machines, it might be helpful to have a recording deck with what is known as the "Sel-Sync" or "SimulSync" feature, which allows one channel of the record head to be used for playback; this permits synchronization between playback of one track and recording of another track. Alternatively, in the absence of this feature, one could record in sound-on-sound fashion, with the second sound being alternatively speeded up and slowed down by exerting appropriate pressure on the takeup or supply reel. With three machines, the problem of synchronization is reduced.


(adapted from Audio magazine, Dec. 1973)

Also see:

High Fidelity from Cassette Systems (Oct. 1973)

Dolby B-Type Noise Reduction System (Sept. 1973)

Equalization in the Home (Nov. 1973)

Cassette Tape Recording Bias (Nov. 1973)

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