he Dual 701 is the quietest turntable ever made. Not only in our judgement, but in that of the first independent test laboratory to evaluate its performance.
This has been accomplished by an entirely different kind of motor, designed expressly for the 701, and a very innovative approach to the problem of resonance.
Instead of the familiar, high speed AC motor, the 701 has an all electronic, low speed motor, with feedback-controlled speed precision.
Because this motor rotates at the record speed, 33 1/3 or 45rpm, the need for speed reduction systems such as friction idler or rim belt is eliminated.
Instead, the platter is rotated directly by the motor, and the record spindle is the top of the motor shaft.
The 701 motor is so quiet and free from vibration that it does not require any isolation mounting, but is mounted directly to the chassis.
Specifications
Platter: non-magnetic, dynamically balanced, detachable 2.9kg
Platter speeds: 33.33 and 45rpm, electronically adjustable
Pitch control: 10% separate for both speeds, each adjusted by means of variable resistor, with calibration scale
Speed control: with illuminated stroboscope
Wow and flutter: < 0.03%
Rumble: < 50dB unweighted
Tonearm: torsionally rigid, tubular tonearm in low-friction four-point gimbal suspension, tonearm counterbalance with two mechanical anti-resonance filters
Source: https://www.vinylengine.com/library/dual/701.shtml