Since the control signals for the lathe automation systems must arrive in advance of the signal to the cutter head, the digital delay units were delaying the audio signal, not the control signal. Instead, the ATR-100 came at a time when a lot of decision makers in the industry had gotten a bit too excited about digital delay lines, which were used in disk mastering installations with the primitive digital delay units available at the time, instead of the good old analog equivalent of the preview head. While Ampex had previously made a preview-head tape machine (the Ampex 300, often used together with Scully disk mastering lathes in the US), which provides the control signals used by the recording pitch and groove depth automation systems of a disk (record) mastering lathe, the ATR-100 was never offered with this option. The ATR-102 was the stereo version, the ATR-104 was the 4-channel version, the ATR-116 was the 16-track version and the ATR-124 was the 24-track version, the last two intended for multitrack recording. The range of Ampex ATR machines was quickly expanded. The head assembly could be plugged in and out to change over between 1/4-inch and 1/2-inch tape.
The tape heads were made of ferrite and the bias frequency used in recording was 432 kHz, as compared with 100-150 kHz used by most other tape machines in the 1970s. It works very well, as evidenced by the widespread acceptance of the ATR-100 in the industry and the many excellent-sounding albums recorded with it. It is still the capstan which controls and regulates tape speed, but the regulation of tape tension is accomplished by electronic means, by active control of the reel motor torque and electromagnetic tensioners. The idea is to provide constant tension throughout the tape, regardless of the amount of tape wound on each reel. The tensioner arms are electromagnetically driven instead of spring-loaded. Interestingly, this size was intended to be directly related to tape velocity multiples (take the circumference, which is 2πr, where r = radius), to provide 7.5 ips (inches per second) at 60 rpm, 15 ips at 120 rpm, and so on. Tension was controlled by a variety and often a combination of means, including spring loaded tensioners, mechanical supply reel braking, electronic supply reel braking, electronic torque control of the takeup reel motor, flywheel rollers, and so on.īy contrast, the ATR-100 has an unusually large diameter capstan, perhaps the largest seen on a tape machine until 1976, at just over 2-3/8 inches OD (outside diameter). Typically, the tension was not constant throughout the duration (playing time) of a reel of tape, but varied depending on the amount of wound tape in each reel. In doing so, it also mechanically decouples the tape path before the capstan from the tape path after the capstan. It increases friction, ensuring the tape remains in firm contact with the capstan and does not slip. Its most striking feature is the absence of a rubber pinch roller! In most, if not all previously-made tape machines, the pinch roller “pinches” the tape against the rotating capstan and is driven by it. Sleger, under the management of Frank Santucci, the ATR-100 was a radical departure from what had previously been done by Ampex or other companies in the design of tape machines. In 1976 they introduced the Ampex ATR-100. They embarked on the design of a new machine, which was to go beyond the established notions of tape transport design. The Ampex 300 tape machine, made in 1957.
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