+
SHERWOOD'S S-7010, one of the lowest-price stereo receivers with genuine "hi-fi" performance, resembles the company's higher price models in external styling, although some convenience features have been eliminated to meet a budget price without sacrificing basic quality.
The S-7010, as one would expect of an under-$200 unit, is a low-power receiver with a rating of 10 watts per channel into 8 ohms from 40 to 20,000 Hz at less than 0.9 percent THD. It does, however, have switching to drive either the regular stereo speakers or two pairs simultaneously, and plugging head phones into its front-panel jack silences all the speakers.
There are inputs for FM, AM, phono, and auxiliary program sources, and three pushbuttons control speaker selection, stereo/mono mode, and tape-monitor functions. The bass, treble, balance, and loudness controls are all conventional, except that the last, unfortunately, has permanent (nondefeatable) loud ness compensation (it also serves as a power switch).
The upper half of the front panel contains the blackout dial with FM and AM scales, a red STEREO indicator, and a relative-signal-strength tuning meter. The FM tuner section carries modest but adequate specifications, which are typified by its IHF sensitivity rating of 2.6 microvolts (µV). In the rear of the receiver are the input and output jacks, screw terminals for MAIN and REMOTE speakers, antenna terminals for 300- or 75-ohm FM antennas and a wire AM antenna (the AM ferrite rod is inside the cabinet), and fuses for the a.c. line and speaker outputs. The Sherwood S-7010 is supplied in a walnut-finish wooden cabinet that measures 17 1/2 inches wide, 9 1/4 inches high, and 13 1/4 inches deep; the unit weighs 14 1/2 pounds. Price: $189.95.
Laboratory Measurements.
The output at 1,000 Hz into 8-ohm loads measured 12.5 watts per channel at the clipping level.
At 4 and 16 ohms, the output was 16 watts and 8 watts. The 1,000-Hz total harmonic distortion (THD) was between 0.05 and 0.1 percent from about 0.1 to 10 watts; intermodulation (IM) distortion was 0.1 to 0.15 percent over the same power range. At outputs under 100 milliwatts (mW), IM increased to 0.36 percent at 10 mW and 0.85 percent at 1 mW.
At rated power and below, THD was generally between 0.05 and 0.1 percent from 45 to several thousand hertz, increasing to 0.3 percent at 20,000 Hz. At half power or less, the low-frequency distortion did not exceed 0.25 percent even at 20 Hz, but at full power the distortion rose rapidly below 40 Hz, where it measured exactly the rated 0.9 percent.
The amplifier required an input of 0.18 volt (Aux) or 1.8 millivolts (mV) at the phono input for its rated 10-watt output. The hum and noise were very low through both inputs, measuring, respectively, -77 and -72 dB. The phono input overloaded at a very safe 67 mV. The tone controls had a range of about ±8 dB at 100 and 10,000 Hz. (This is good design for a low-power amplifier that could easily be overdriven by excessive boost.) The tone-control curves were "shelved," affecting a wide portion of the spectrum to almost the same degree.
The loudness compensation boosted only the low frequencies. The RIAA phono equalization was accurate to within ±0.5 dB from 30 to 20,000 Hz. Cartridge inductance had minimal effect on the phono response, with the output rising by about 1 dB between 6,000 and 15,000 Hz and falling off I dB between 15,000 and 20,000 Hz. In this respect, the S 70 I 0 was one of the better receivers we have tested.
The IHF FM sensitivity was 2.4 /AV in mono and 5 µV in stereo. The 50-dB quieting sensitivity was 3.5 µV in mono and 40µV in stereo. Ultimate quieting was 9 dB better than the rated 60 dB in mono and 62 dB in stereo. Distortion was 0.12 percent in mono and 0.32 percent in stereo. The automatic stereo/mono switching threshold was be tween 4 and 5 µV (the tuner does not have FM interstation-noise muting).
Most of the other FM tuner measurements were also better than rated (ratings are in parentheses): capture ratio, 3 dB (4 dB); AM rejection, 50 dB (45 dB); and alternate-channel selectivity, 47 dB (40 dB). The image rejection of 48 dB was close to the rated 50 dB, and the 19-kHz pilot-carrier leakage was 42.5 dB below 100 percent modulation.
The FM frequency response rose slightly in the 2,000- to 12,000-Hz range, but met the specification of ±-2 dB from 30 to 15,000 Hz.
The FM channel separation of the tuner was exceptional, exceeding 25 dB from 30 to 15,000 Hz and typically measuring 30 to 32 dB. The AM frequency response was flat from 20 to 2.000 Hz, and down 6 dB at 4.000 Hz.
Comment.
It would be an understatement to say that we were impressed with the Sherwood S-7010. It does not represent any breakthrough in technology or performance, but it is a thoroughly competent little receiver that gratifyingly sells for a fraction of the price of many of the stereo receivers we have seen in recent months.
Very little has been sacrificed in performance to achieve the unit's low price. The audio power is modest by today's standards, to be sure, and the S-7010 should therefore be used with fairly efficient speakers for best results.
As for the FM tuner, its performance speaks for itself. In the important areas of effective sensitivity, noise, and distortion (to say nothing of uniform channel separation across the audio frequency range), the S-7010 ranks with some of the most highly regarded tuners and receivers.
Some of Sherwood's more expensive receivers feature the "Dynaquad" connection, which can be used to drive four speakers for simulated quadraphonic sound by ambiance recovery. Although the manual does not mention it, this is also possible with the S-7010 (and many other units with the same speaker switching configuration). Simply connect the rear speakers in series, with their "+" leads to the REMOTE speaker terminals and their "-" leads joined together and floating. Ideally, a resistor of 8 to 10 ohms, 5 or 10 watts, should be connected from this junction to common, but even this can be omitted with little loss of performance. When the speaker (A + B) button is pushed to activate both main and re mote speakers, this connection gives an excellent ambiance enhancement to either stereo or matrixed quadraphonic programs.
The Sherwood S-7010 (as you may have gathered) is a lot of receiver for the money. It sounds good, looks good, and feels good, and the price is right. We are happy to see that gal loping inflation has not completely eliminated the possibility of a good budget high-fidelity system based on a receiver such as the Sherwood S-7010.
-----------
The levels of both random noise and THD (which includes noise and distortion) are compared with the audio-output level as input-signal strength increases. Both mono and stereo are shown.
Also see:
Sony ST-4950 AM/FM Stereo Tuner