Denon DP-33F Vintage Direct Drive S arm Servo Control, izgst

The denon dp-33f is a two-speed direct-drive record player with complete front-panel control of tone-arm operation. The lateral position of the tone arm can be shifted (by means of a servomotor) over its full playing area with a front-panel knob. In addition there is full cueing, start/stop control, and adjustment of the antiskating torque from the front—and all with the dust cover lowered.

The cast-aluminum platter of the denon dp-33f, which together with its 1/4-inch-thick rubber mat weighs 3-1/2 pounds, is driven by an a.c. Direct-drive motor whose speed (33-1/3 or 45 rpm) is controlled by a quartz-crystal oscillator. The inside of the platter rim has a magnetic coating containing recorded impulses which are sensed by a pickup head (similar to the playback head of a tape deck) as the platter turns. The resulting electrical impulses provide rotational-speed feedback to the servo system that controls the turntable operation.

The operating speeds are not adjustable but are maintained within 0.002 Per cent of their nominal values by the quartz oscillator. Stroboscope markings are cast into the bottom of the platter rim and are visible from the front through a mirror system. A single set of markings suffices for both speeds, since they are illuminated by a light controlled by the same crystal oscillator that serves as a reference for the turntable rotation.

The tone arm of the dp-33f is a conventional s-shaped tubular pivoted arm whose threaded counterweight carries the tracking-force scale (calibrated at 0.1-Gram intervals from 0 to 2.5 Grams). The arm has a standard four-pin plug-in shell containing a rubber insert against which the cartridge is mounted, presumably to help damp resonances in the cartridge/shell system.

The principal difference between the dp-33f and some other high-quality record players is its servo-driven tone arm. This is not a feedback control system, but rather a motor drive that enables the user to position the arm anywhere on the record surface by turning a small knob on the sloping control panel of the record player. The same control initiates the playing cycle when it is pressed down. Another electronic control button raises and lowers the tone arm and a knob control varies the antiskating torque, making the arm fully controllable with the transparent dust cover lowered.

The power switch of the dp-33f is at the left of the panel, and next to it is a slim rectangular button that selects either 33-1/3- or 45-rpm operation. To the right of the speed selector is a small antiskating knob calibrated from 0 to 3 grams.

Much of the normal operation of the record player is handled by a small skirted knob marked locate/start. It has calibrations marked 30 and 17 (centimeters, denoting the diameters of 12- and 7-inch records). With a record on the turntable, the knob is set to the appropriate diameter and momentarily pressed down. This causes the arm to move in to the selected diameter and stop. A couple of seconds later the motor starts and the arm descends to play the record. To move the arm laterally at any time, one merely presses the button (which raises the arm from the record) and turns the knob until the pickup is over the desired point. The response of the arm to the knob rotation is very rapid over most of the adjustment range, but it slows markedly as one approaches either the 30- or the 17-cm calibrated diameter. When the arm has been cued, releasing the control allows it to descend at that point. At the end of play, the arm returns to its rest and the motor shuts off. Fully manual operation is also possible, since lifting the arm from its rest and moving it toward the platter will start the motor.

Engaging the repeat button causes the record to be replayed indefinitely, starting from the diameter for which the locate knob is set. Pressing a similar lifter button raises the arm slowly, and releasing it from its latching position lowers the pickup smoothly to the record surface. The remaining control is a stop button, which interrupts the playing cycle at any time and returns the arm to its rest.

The denon dp-33f is finished, for the most part, in satin silver, with a black control panel and a clear plastic cover that remains open at any angle. It is mounted on softly sprung feet for isolation from mechanical and acoustic vibrations.

Laboratory measurements: the denon dp-33f was tested with a shure m97he cartridge installed in its arm. The cartridge was operated with an effective force of 1.25 Grams. The capacitance to ground of the signal cables and arm wiring was 81 to 89 picofarads, and their interchannel capacitance was 4 picofarads. With the arm balanced correctly, the actual vertical force was exactly equal to the setting of the force scale. The tracking error was also very low, less than 0.25 Degree per inch for radii of 2.5 To 6 inches, with zero tracking error measured at radii of 2.5 And 5 inches.

The effective arm mass was 15 grams, a moderately low value for this type of arm. The stylus compliance of the shure cartridge resonated with that mass at about 9 hz (with its stabilizer raised), giving a “double humped” response with peaks at 9 and 5.5 Hz. When we lowered the dynamic stabilizer of the cartridge, the low-frequency resonance was a barely detectable 1-db rise at 9 hz.

The unweighted turntable rumble was - 38 db, and with arll weighting it was - 62 db. Both figures represent excellent performance, above the average for similar turntables we have tested. The rumble was primarily at frequencies below 10 hz except for a low-level peak at 40 hz. The flutter was 0.06 Per cent in a jis (weighted rms) measurement and ±0.08 Per cent weighted peak. The flutter spectrum was principally under 12 hz.

The automatic operation of the record player was flawless, and it was completely silent both electrically and mechanically. With the locate knob set to 30, about 3 seconds were required for the arm to reach the record's lead-in groove after the control was pressed. Since the motor turns on only after the arm is in place, another 5.5 Seconds elapsed before playing started. The total start-up time of 8.5 Seconds was somewhat faster than that of most automatic turntables. When we caused the arm to slew from its 30-cm diameter to its 17-cm diameter, some 11.5 Seconds were required for playing to resume.

The arm lift raised the pickup in less than 1 second and lowered it in about 3 seconds. There was absolutely no detectable lateral arm drift during the raising and lowering operations. The antiskating dial was very accurately calibrated, so that setting it to match the vertical force did, in fact, result in equal tracking ability for the two channels. The vibration isolation afforded by the mounting feet was somewhat better than average for a direct-drive turntable, with the principal transmission mode in the audio range being at 50 hz.

Comment: it is difficult to find much of a substantive nature to criticize in the denon dp-33f. It is, in most respects, a conventional, very high-quality record player. In no respect was it inferior to any comparable player we have tested, and in practically every performance category it ranked among the best of its type. In both design and construction, it follows the denon tradition of superior quality

with that said, we must comment on its real claim to novelty, the servo-driven tone arm. As mentioned earlier, this is not a motional-feedback-controlled arm such as those available from sony and jvc. While playing a record it is indistinguishable from almost any other s-shaped tubular arm (in its basic performance, that is; we are not concerned here with the subtle effects of such features as the rubber-damped cartridge-mounting surface in the headshell, or with the possible sonic effects of its soft, heavy rubber mat).

I have long felt that the need to lift the dust cover to cue a record, raise or lower the arm, or even to turn a record player on or off is an unnecessary inconvenience. It tends, i think, to discourage the lowering of the cover while playing records, defeating its functional hygienic purpose (analogous is the manner in which poorly designed, uncomfortable seat belts in many cars have discouraged people from using them). In addition, a raised dust cover renders any turntable far more susceptible to acoustic feedback. Gradually, record-player manufacturers have made the major operating controls accessible at the front of their products and outside the covered area. Nevertheless, until recently very few had their cueing (arm-lift) controls so accessible, negating much of the advantage of having any of the other controls at hand. And anyone wishing to play specific selections within a record rather than the entire disc was almost always limited to manual tone-arm cueing.

The denon dp-33f answers these objections very neatly. Of the possible operating actions that could be applied to a record player, only the stylus-force adjustment remains inaccessible when the cover is lowered. To compensate for that minor lack, the unit is the only player with a truly accurate and effective antiskating adjustment that is usable while a record is being played and with the cover down. The arm locate function, which seems a trifle strange when first used, is really simple, smooth, and quite accurate.

The denon dp-33f, then, earns high marks for total record-player performance, especially when the often neglected human-engineering factors are included. All of this, combined with denon’s traditional quality, makes this a unique and desirable product at a reasonable price.

Specifications: drive method: direct drive motor: ac servo motor platter: 300mm, 1.5Kg diecast aluminium speeds: 33 and 45rpm wow and flutter: 0.015% Wrms signal to noise ratio: 78db tonearm: static balance type effective length: 220mm overhang: 16mm cartridge weight range: 5 to 9g dimensions: 450 x 403 x 140mm weight: 9.8Kg

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