Dual direct-drive turntables (Advertisement, Jan. 1979)

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If the bass isn't, as clean as you'd like ....

The problem may be your tonearm. Not your amplifier or speakers.

Above: Dual 604 direct-drive turntable.

--- Cutaway view of anti-resonance counterbalance. (A feature of Dual models 604, 621, 721 and 1246)

--- Solid lines show effectiveness of anti-resonance filters in damping resonant amplitudes of three different cartridges (compliance 15, 25 and 43 x 10^-6 cm/dyne). Broken lines show higher resonant amplitudes with conventional counterbalance.

If you've been wondering why your high-powered amplifier and great speaker system don't deliver deep bass as cleanly as you'd like-especially at high listening levels--the problem may well be the effects of resonance on the stylus.

Ideally, the stylus should move only in response to the contours of the record groove. But in reality, the stylus tip also responds to various resonances: its own (with the stylus shank) and the combined resonance of the tonearm/cartridge system.

These subsonic frequencies, though inaudible in themselves, can have very audible effects. Especially with warped records. They can drain amplifier power and cause excessive movements of the low frequency driver. They can cause the tonearm to vibrate and even to momentarily leave the groove. All of which results in audible distortion.

Competent tonearm designers know all this and do their best with materials, masses and compliances to establish the inevitable resonances at the least harmful frequencies, (usually between 8 and 10 Hz) and with the lowest possible amplitudes.

Dual's tonearm designers have taken a significant step beyond this.

The unique counterbalances of our direct-drive models (604, 621 and 721) and our top belt-drive multiple-play model (1246) contain two mechanical anti-resonance filters.

These are specially tuned to damp resonant energy in the tonearm/cartridge system and chassis.

The startling effectiveness of these filters in lowering the resonant amplitude of three cartridges having different compliances can be seen in the graph. Whether the improvement in the bass is subtle or obvious to you depends on the other components and your listening environment.

We've prepared a technical paper on this subject which we'll send to you if you write us directly. You may discover that you don't have to replace your amplifier or speakers after all.

DUAL -- For the life of your records United Audio, 120 So. Columbus Ave., Mt. Vernon, NY, 10553, USA.

(Source: Audio magazine, Jan 1979; )

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