Denon DRA-300 A/V receiver Review

The Denon DRA-300 is a moderately powered, moderately priced stereo receiver with digital-synthesis tuning for both the AM and FM bands. Its audio amplifier section is rated to deliver 33 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.05 per cent total harmonic distortion. According to Denon, the power amplifiers employ a “non-switching” variable-bias circuit that reduces high-frequency distortion.

The DRA-300 has most of the operating features one looks for in a modern stereo receiver, including station memories (five each for AM and FM), a large, legible, digital frequency display, and pushbutton tuning controls with frequency steps of 100 kHz for FM and 10 kHz for AM. The bass and treble tone controls are operated by small knobs with center detents, and separate buttons activate the two sets of speaker outputs. The front panel also contains a power switch and a headphone jack.

Input switching is controlled by pushbuttons, with green LED’s showing which source has been selected. The inputs include AM, FM, phono, and a high-level input marked dad/aux for a digital Compact Disc player (on the Japanese market the CD is known as the “DAD,” or Digital Audio Disc). The subsonic filter button engages an infrasonic filter that cuts off signals below 15 Hz at 6 dB per octave, and pressing the fm mode button switches the tuner to mono and disables the interstation-noise muting for reception of weak signals. The loudness compensation is controlled by a button below the large volume knob. The DRA-300 can be used with two tape decks, and a knob on the panel connects them for dubbing from either one to the other.

Next to the display window is a group of tuning controls. Long UP and down buttons step the tuning by one interval per operation. Holding a button in causes the tuner to step repeatedly, but there is no automatic scan or signal-seek feature, so some time may be needed to cover the entire tuning range. Five smaller station-preset buttons and a memory button are used in the conventional manner to store station frequencies. Unlike most receivers, which often have rather elaborate signal-strength or tuning indicators, the DRA-300 has only a single green LED, which shows that a signal of receivable strength has been acquired, and a red LED stereo indicator.

The rear of the receiver contains the usual signal input and output jacks, bind-ing-post antenna terminals, and a detachable hinged AM loop antenna. The spring-loaded speaker terminals accept the stripped ends of the speaker wires. One of the two a.c. outlets is switched. The Denon DRA-300, finished in silver gray, measures about 17 inches wide, 16 inches deep, and 4-1/2 inches high. It weighs 16-3/4 pounds. Price: $299.

Laboratory Measurements

Its moderate power rating and generous dimensions combined to keep the DRA-300 cool throughout our tests. The internally mounted output-transistor heat sinks are convection-cooled by air entering at the bottom of the receiver and exiting at the top.

With both channels driving 8-ohm loads, the output waveform clipped at 43 watts per channel, corresponding to a clipping headroom of 1.13 dB. Unlike most other receivers (and separate amplifiers as well), the DRA-300 was able to deliver about the same power into lower load impedances, with clipping outputs into 4 and 2 ohms of 47 and 45 watts per channel, respectively. The short-term output was very high during the 20-millisecond bursts of the 1,000-Hz signal used for the dynamic-headroom measurement, measuring 100 watts into 8 ohms, 68 watts into 4 ohms, and 66 watts into 2 ohms. The 8-ohm reading, in particular, was so good that we doubted its validity, but it was confirmed by repeated measurements. This gives the DRA-300 a dynamic headroom of 4.8 dB, which is the highest we can recall measuring on any receiver or separate amplifier to date.

The 1,000-Hz harmonic distortion with 8-ohm loads rose smoothly from 0.013 per cent at 0.1 watt to 0.13 per cent at 40 watts. With 4-ohm loads, the readings were 0.02 per cent at 0.1 watt and 0.11 per cent at 40 watts. Even 2-ohm operation gave completely acceptable distortion readings, from 0.022 per cent at 0.1 watt to 0.09 per cent at 30 watts. Only at 40 watts did distortion become significantly higher, measuring 0.3 per cent.

Judging by the nearly constant distortion readings we obtained across the audio-frequency range, Denon’s “non-switching” circuit appeared to be fulfilling its promise. At the rated 33 watts per channel (into 8 ohms) the distortion was between 0.08 and 0.09 per cent from 20 to 1,000 Hz, falling to between 0.05 and 0.06 per cent from 2,000 to 20,000 Hz (in most amplifiers, distortion rises appreciably at the higher audio frequencies). At half power and one-tenth power, the distortion curves had the same shape, but the readings were considerably lower at reduced power levels (typically 0.01 to 0.02 per cent over the full range at 3.3 watts, which corresponds to a comfortably loud listening level for most people).

The IHF intermodulation distortion (mixed 18- and 19-kHz input frequencies) was —66 dB at 1,000 Hz and — 69 dB at 17 and 20 kHz. The amplifier was stable with a simulated reactive speaker load (showing only moderate ringing on a 10,000-Hz square wave). The slew factor was 3, with a full-power sine wave taking on a triangular shape at about 60 kHz.

The amplifier sensitivity, for a reference output of 1 watt, was 26 millivolts (mV) at the dad/aux input and 0.4 mV at the phono input. The corresponding A-weighted noise levels were —78 and —73.5 dB. The phono input overloaded at a high level, from 157 to 222 mV depending on frequency. The dad/aux input overloaded at 3.1 volts, which should not cause problems in a home system (very few sources will reach that level even on peaks, and the CD players we have tested typically have a maximum output of 1.5 to 2 volts), but it is well to be aware of the input limitation. The phono input resistance was 47,000 ohms, shunted by a very low capacitance of about 20 picofarads.

The RIAA phono equalization was very accurate (within 0.5 dB of the ideal response from 20 to 20,000 Hz) and was not significantly affected by cartridge inductance. The tone-control response curves were hinged at about 500 Hz for the bass control and 1,000 Hz for the treble control.

The basic amplifier response at high frequencies (above about 6,000 Hz) was slightly affected by the volume-control setting (this is not unusual), and the subsonic filter showed a rolloff beginning at 100 Hz and amounting to 7 dB at 20 Hz. The loudness compensation boosted both low and high frequencies as the volume level was reduced.

In mono, the FM tuner usable sensitivity was 16.3 dBf (3.6 microvolts, or μV), and the stereo switching threshold was at 29.3 dBf (16 μV). The 50-dB quieting sensitivity was 23.3 dBf (8 μV) in mono and 39.2 dBf (50 μV) in stereo. FM distortion at 65 dBf (1,000 μV) was 0.13 per cent in mono and 0.18 per cent in stereo. The mono and stereo noise levels at 65 dBf were —77 and —70 dB, respectively.

Other FM performance parameters included a capture ratio of 1.55 dB, AM rejection of 54 dB at 45 dBf (100 μV), and a marginally acceptable image rejection of 37 dB (although it is rated at only 45 dB). Selectivity was fairly good, 59 dB and 4.7 dB for alternate- and adjacent-channel spacings, respectively. The muting threshold was 30.2 dBf (18 μV). The 19-kHz pilot-carrier leakage into the audio was a rather high —50 dB, but the tuner hum was a low -73 dB.

The FM frequency response was flat from 30 to 1,000 Hz, rising slightly to +1.5 dB between 10,000 and 13,000 Hz and still up almost 1 dB (relative to 1,000 Hz) at 15,000 Hz. The channel separation was about 43 dB from 150 to 2,000 Hz, falling to 34' dB at 30 Hz and 37.5 at 15,000 Hz. The AM-tuner frequency response was quite limited, down 6 dB from the maximum (between 200 and 300 Hz) at 28 and 2,100 Hz.

Comment

The Denon DRA-300 is noteworthy both for what it does and what it does not do. It departs from convention in not having any signal-strength indicator (other than the “go/no-go” light). But most people probably have little need for a signal-strength indicator, and the four- to five-segment LED displays devoted to that function on most receivers rarely convey much useful information beyond what is already obvious to the ear.

The DRA-300 lacks any rapid means of scanning the FM band; doing so by holding in one of the tuning buttons is a rather slow process. But once all the station presets have been entered, few listeners scan the entire band anyway. A built-in lithium battery maintains the preset memories when the receiver is turned off (for as long as five years, according to Denon, even if the receiver is not plugged into a powered socket!). Although the level of the 19-kHz pilot carrier in the tape outputs was undesirably high for taping FM broadcasts with Dolby noise reduction, most Dolby-equipped cassette decks have multiplex filters to deal with just such a situation.

These are all, in any case, minor criticisms. The most novel aspect of this receiver is something not mentioned in its specifications—its ability to drive the lowest-impedance speaker loads at a high power level without distress to itself or to listeners. As regular readers of these test reports know, amplifiers that are comfortable driving 2-ohm loads are not at all common, even at high prices, and low-priced receivers with that quality are exceedingly rare. It may not be audible during casual listening, but it is good to know that your receiver can deliver its full performance regardless of the speakers connected to it. Moreover, the DRA-300’s very high dynamic headroom should enable this apparently low-power receiver to sound more like one with two or three times its power rating—and to cope well with the high peaks encountered in playing digital Compact Discs.

Overall, the Denon DRA-300 combines some fairly standard features and performance parameters with others that are truly outstanding. It provides excellent performance in those areas that really matter, at a reasonable price and in a relatively plain wrapper, without most of the flashy trappings of too many consumer electronics products today. Let us hope that the DRA-300 signifies the start of a trend in receiver design.

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