Onkyo DX-7500 CD-player Review

The Onkyo DX-7500 is a full-featured CD player incorporating the latest digital technology, but it is priced just above a typical midrange player. It features dual 18-bit digital-to-analog (d/a) converters with eight-times oversampling (at 352.8 kHz). The player also makes extensive use of optical signal transmission and isolation techniques.

Onkyo’s Opto-Drive system is claimed to completely eliminate any electromagnetic interference from the outputs of the d/a converters by using phototransistors instead of diodes to regulate the power-supply voltage to the converters. Optical coupling between the digital and analog circuitry of the DX-7500 eliminates the possibility that digital signals could leak into the analog sections and degrade the output quality. The analog audio outputs are supplemented by two digital outputs (electrical and optical) for use with an external d/a converter.

In addition to its internal sophistication, the DX-7500 offers almost every feature one could hope to find in a CD player. Besides the usual operating functions, including repeat of a track, disc, or any selected portion, it has a Time Editing feature that determines how many tracks can be accommodated on each side of a tape cassette. When you’re copying a CD, this feature automatically puts the player into pause mode at the end of the tape’s first side to allow the cassette to be turned over.

The memory system can be programmed to play up to twenty tracks of a CD in any order, and a Memory Edit feature allows the program to be modified at any time. The player has a shuffle-play mode, in which all the tracks on a disc are played back in a random order. It also provides direct keypad access to any numbered track.

The rear of the DX-7500 has three pairs of analog output jacks, identified as fixed, variable, and direct. The direct output bypasses the player’s analog filtering, minimizing the circuitry between its d/a converters and the system amplifier. The manual warns that recording on a cassette deck from the direct outputs may result in “beat” sounds on the tape similar to those sometimes experienced when recording from an fm tuner with inadequate ultrasonic filtering.

Unlike most CD players, the DX-7500 has a front-panel volume control for its variable analog outputs as well as the headphone jack. The volume knob is motor-driven so that it can be operated from the supplied wireless remote control. Besides the analog and digital outputs (optical and coaxial), the rear apron has two small phone jacks for linking the DX-7500 to other Onkyo audio and video components for unified system control.

The easily read white front-panel display of the DX-7500 shows track and index numbers and elapsed or remaining times on the track and disc. The LAP/REM button toggles the time display, and there is an index button for cueing. The lower part of the display shows the status of the program memories, including the remaining tracks on the disc or in the program and the order in which they will be played.

The Onkyo DX-7500 is a heavy, solidly constructed player. Its disc-transport mechanism is made of metal, unlike the light, plastic construction used in low-cost players. It can play 3-inch discs without an adaptor ring.

The supplied remote control duplicates virtually every front-panel function, including opening and closing the disc drawer. In addition, it has a CD/tape switch, enabling it to operate an Onkyo cassette deck as well, an intro-scan button to play the first 7 seconds of each track on a disc, and an auto-space button to insert a 4-second pause between tracks during taping. The DX-7500 measures 17-1/8 inches wide, 14-1/2 inches deep, and 5-1/8 inches high, and it weighs about 19-1/2 pounds. Price: $700.

Lab Tests

The output of the Onkyo DX-7500 was almost exactly 2 volts, as rated. Its frequency response was flat within ±0.1 dB from 20 to 20.000 Hz, with a channel imbalance of 0.04 dB. The interchannel phase shift was less than 0.4 degree from 20 to 20,000 Hz.

The linearity of the d/a converters was virtually perfect down to a — 70-dB level. At — 80 dB the output was low by 0.5 and 1.5 dB for the left and right channels, respectively. At — 90 dB, the left-channel output was exactly — 90 dB, while the right channel was 2 dB low. The error at — 100 dB was +2.5 dB for the left channel and +1.3 dB for the right channel.

Channel separation was greater than 120 dB at 100 Hz, a very high 111 dB at 1,000 Hz, and 80 dB at 20.000 Hz. The total harmonic distortion (thd) plus noise at a 0-dB level was between 0.003 and 0.006 percent from 20 to 20,000 Hz. At 1.000 Hz, the distortion was less than 0.003 percent for recorded levels from — 10 to — 80 dB.

The A-weighted noise level measured during the “infinity zero” track of a test disc, when the d/a converters were essentially not operating, was — 100 dB in the left channel and — 109 dB in the right channel. In effect these figures represent the noise level of the player’s analog section. The quantization noise (with the converters active) was about —90 dB. The dynamic range was 92 to 94 dB. The frequency error of the player’s output was less than 0.02 percent.

The DX-7500 had no difficulty tracking the highest-level defects (900 micrometers) on the Philips TS5A test disc. Since this disc is no longer adequate to test the error-correction capabilities of a late-generation CD player, however, we have begun to use the new “Digital Test” CD on the French Pierre Verany label, which contains calibrated “defects” in a range that is almost certain to overtax the capabilities of any CD player at some point. The Onkyo DX-7500 was able to track the 1,000-micrometer levels on this disc, although a 1,250-micrometer defect produced crackling noises in playback.

The slew time from Track 1 to Track 15 of the Philips TS4 disc was 1.8 seconds, which is very rapid, though not quite the fastest we have seen. The cueing accuracy was excellent. The only respect in which the DX-7500 did not more than live up to our expectations was in its impact resistance. It was able to absorb a fairly solid slap on a side without mistracking, but even light finger taps on the top cover would interrupt playback for a moment, after which it almost always returned to the point where it had stopped. Fortunately, it appeared that the player’s physical isolation through its mounting feet was considerably more effective.

Comments

The measured performance of the Onkyo DX-7500 ranks with the best we have seen from any CD player, including some selling at considerably higher prices. It is difficult to assess the audible benefits of the measurable qualities of a CD player. Personally, I do not find significant differences in sound quality between most CD players. That does not mean they all sound alike, of course, merely that the differences, for me at least, do not warrant a conclusion that one is better than another.

I can say that the Onkyo DX-7500 sounded at least as good as any other CD player I have heard, and it also has just about every useful feature that can be found in any other player. Its front-panel volume control (remotely controllable as well) makes it possible to drive a power amplifier directly from it, and that is the way I operated the player for listening purposes. Whether you’re looking for the latest refinements in CD player technology or just want a full-featured, high-performance machine at a reasonable price, the DX-7500 would be hard to beat.

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