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TENTROL is a tape tension control kit which is active in the Record and Reproduce modes of a tape recorder.

TENTROL may be used to control either the holdback or the takeup tension (or both), depending upon whether it is installed on the existing supply or takeup motors.

TENTROL does not disturb the tape path, utilizing instead a tachometer that is attached to the reel motor.

The Model 400-01 and 400-02 kits will control holdback tension on Ampex Models 440C and 440C-8 respectively.


  • Speed and timing accuracy are improved because capstan slippage caused by excessive tension differential across the capstan is significantly reduced.

  • Pitch change from beginning to end of reel is eliminated since it is caused by change in tape length with tension variations.

  • Poor transport starting characteristics, caused by capstan slippage while the reel idler accelerates, can be eliminated by the reduction of excessive tension.

  • Head life can be increased by eliminating excessive tape tension.

  • High frequency response is improved through consistent head-to-tape pressure and through reduction of tape tracking, and consequent azimuth variations caused by tension changes.

  • Accelleration of heavy reels, fast-start capability with 14-inch reels and variable tensionwith pack diameter can be gained by installing TENTROL on the takeup motor (see manual).



Applicable To

Ampex Models 300, AG 300, 350, AG 350, 351, 354, AG 440, AG 440-8, AG 440B, 3200 and 3300 Duplicator Transports.

Tape Widths

150-mil Cassette; quarter-, half-, and one-inch

Reel Sizes

“Cine” (1-7/8” hub) through 14” with NAB hub

Nominal Constant Tension at Head

  • Adjustable from 3 to 9 ounces within motor torque limits.
  • High tensions at the lower tape speeds will cause the motor to overheart unless forced ventilation is available.

Tension Variation Throughout Reel

± 1/2 ounce

Maximum Torque Available

90% of maximum rated motor torque

Power Line Voltage

50 or 60 Hz.

Additional Features

  • Adjustable starting torque for optimum starting characteristics.
  • Two tension adjustments allow for close matching of tension requirements to the motor characteristics and provide the capability of changing tension with pack size for special requirements.
  • A switch on the Control Module allows selection of constant torque operation for special requirements.