Denon DP-52F Turntable Review

The Denon DP-52F turntable has a two-speed (33-1/3- and 45-rpm) quartz-lock direct-drive a.c. motor driving a cast alloy platter weighing (with its rubber mat) about 3 pounds. Recorded around an inner circumference of the platter are some 1,000 magnetic pulses that are sensed by a small magnetic pickup head to provide speed-control feedback information to the servo system. The DP-52F is mounted on a handsomely finished high-gloss wood-grain base together with a “Dynamic Servo Tracer” tone arm. The entire base is supported on four softly sprung adjustable feet; the unit is equipped with a hinged, clear-plastic dust cover.

The upper surface of the rubber turntable mat is illuminated by a LED in a cylinder next to the arm base. The turntable and mat have three pairs of holes spaced 120 degrees apart at radii of approximately 2-1/2 and 4-3/4 inches. Below the platter are two photocells that sense the light passing through either or both sets of holes. If no record is on the turntable, light passes through both sets of holes and the arm does not move from its rest (the platter shuts off in a couple of seconds). A 12-inch record covers all the holes, signaling the microprocessor in the control system to start the turntable at 33-1/3 rpm and index the arm for a 12-inch record. A 7-inch record covers only the inner group of holes, causing the motor to turn at 45 rpm and the arm to index to a 7-inch diameter. Nonstandard records such as 7-inch 33-1/3-rpm, 10-inch of any speed, or 12-inch 45-rpm can be played with manual speed selection and modification of the tone-arm indexing.

The Dynamic Servo Tracer tone arm operates in a balanced condition (by means of a threaded counterweight adjustment at its rear). The downward force is applied electronically by a built-in torque servo controlled by a small dial next to the arm base. The force calibrations cover from 0 to 3 grams at 0.1-gram intervals. The motion of the arm is controlled in both vertical and horizontal planes by its servo system, with a fixed percentage of the vertical force being applied horizontally by the horizontal torque motor. This automatically supplies the correct antiskating compensation for any tracking-force setting.

A second control dial, calibrated over the same range as the stylus-force/antiskating dial, is marked q-damping. It controls the damping of the arm resonance in both planes through its servomotors. The arm itself is a straight low-mass tube with a plugin cartridge shell. The effect of the electronic damping is to place the arm/cartridge resonance close to the ideal frequency of 10 Hz and to damp its amplitude.

The operating controls of the Denon DP-52F are soft-contact rectangular pushbuttons on the sloping upper front panel outside the area protected by the plastic cover. Power is applied by the left-most button, near which are individual manual speed-se-lection buttons (not needed in normal operation). A touch on start places the platter in motion at a speed determined by the record size (speed can be changed manually after starting). The arm moves to the appropriate diameter and descends to the record surface. The arm lifts after play, the motor stops almost instantly (it has electronic braking), and the arm returns to its rest. The stop button produces the same effect whenever it is pressed, and the repeat button causes a record to be repeated until the button is pressed a second time. The lifter button raises and lowers the tone arm on alternate operations with a smooth yet rapid motion.

The DP-52F also has an electronic system, operated by the play and stop buttons, that gives full control over the arm movement even while the cover is down. Pressing the start button while the pickup is on the record raises it and causes the arm to move slowly toward the center of the record. When the button is released, the arm stops and descends to the record. Similarly, a light pressure on the stop button lifts the arm and causes it to move outward with the same stop-and-descend sequence when the button is released. When using stop in this manner, care is needed not to press it too hard, since that will immediately stop the turntable and return the arm to its rest. After a little practice, one learns how much pressure is permissible for arm indexing.

Denon’s Model DP-51F is identical to the DP-52F except that it has a vinyl wood-grain base and lacks the tone-arm lateral-movement feature; its price is $425.

Laboratory Measurements

We installed a Shure M97HE cartridge in the plug-in shell of the DP-52F for our tests. Although no installation instructions were supplied with our review sample (one of the first to enter this country), a trial-and-error process showed that a 38-mm distance from the stylus to the end of the arm tube gave the lowest tracking error, less than 0.4 degree per inch for radii of 2.5 to 6 inches. The applied stylus force was exactly equal to the dial calibration up to 1.5 grams and typically within 10 per cent of it above that force.

The effective arm and cartridge mass (the cartridge weighs 6.4 grams) was only 14 grams with the power off (no damping or servo action to control the arm resonance). Switching on the power dramatically reduced the apparent effective mass to a mere 7 grams, since the bulk of the work needed to move the arm system was now done by the servomotors instead of by the record groove via the stylus tip. The difference in resonance amplitude between the powered and unpowered states was also most impressive: it was difficult to find the tone-arm resonance when the Dynamic Servo Tracer was functioning.

The low-frequency resonance of the M97HE stylus and the total effective arm mass was at about 9 Hz. The q-damping dial had to be set to zero for this measurement, since it damped the resonance so effectively when set to the tracking force that we could not identify its frequency. The antiskating compensation was correct, using the criterion of equal distortion in both channels when playing discs recorded at a very high velocity. The arm lift operated rapidly and precisely, with no detectable lateral shift during its up/down cycle. The capacitance to ground of the arm and signal wiring was 80 to 90 picofarads per channel, with a very low interchannel capacitance of 1 picofarad.

The non-adjustable turntable speeds were exact, and the unweighted rumble was a low — 40 dB, improving to —61 dB with ARLL audibility weighting. The rumble spectrum covered the range from 5 to 35 Hz with no significant peaks within it. The flutter was 0.05 per cent weighted RMS and ±0.07 per cent weighted peak, with the flutter spectrum limited to the 3- to 8-Hz range. The auto cycle times were 7.5 seconds for start and 9.5 seconds for stop (from the end of a record). The isolation of the record player from base-conducted vibration was excellent, with responses only at 20 and 40 Hz and between 150 and 250 Hz.

Comment

The DP-52F is about as automatic and foolproof a player as most users could desire. Although a rare translucent record might be able to fool its photoelectric sensing system, with ordinary records everything worked perfectly, and it was impossible to make the player do anything that could result in pickup damage.

The arm-positioning control also worked well and was very easy to use, except that when the speed had to be changed manually after initiating the operation (as for a 7-inch 33-1/3-rpm record) even a light touch on stop would sometimes shut off the player.

We played our collection of warped records to check the effectiveness of the Dynamic Servo Tracer tone arm. It was soon evident that this arm could track any record that we had ever been able to play with any other arm of any type (including tangential) at the minimum force of which the Shure cartridge was capable (0.75 gram). Other than with a grotesquely warped record that must have been stored on a hot radiator, the DP-52F simply did not recognize the existence of record warps as an impediment to tracking.

Overall, the Denon DP-52F is one of the most thoroughly engineered record players we have used. Though quite conventional in its externals, it is an exceptionally refined and handsome product with an utter ease of operation that makes it a delight to use.

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