Latest Audio Equipment and Accessories
Sherwood Receiver Has Low-Distortion Amplifier
Sherwood's S-2680 CP AM/FM stereo receiver uses slide controls for bass, treble, balance, and volume, pushbuttons for all other receiver functions. Those functions include eight AM and eight FM station pre sets, auto-scan or manual tuning, input selection, loudness compensation, muting tape monitor, and power. Connections and switching are provided for two tape decks and two speaker pairs in addition to a pair of phono inputs. A bass-EQ function sup plies an ultra-low-frequency bass boost to flatten the response of bookshelf speakers.
Displays include those for output power, station frequency, signal strength, and FM stereo.
The FM tuner circuit incorporates a dual-gate MOSFET input stage, ceramic i.f. filters, quadrature detector, and PLL multiplex decoder. The power-amplifier section is a "sliding class-A" design with an input stage configured to minimize both "hard" and "soft" transient intermodulation distortion. The unit is rated to deliver 70 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.008 percent total harmonic distortion. Price: $479.95.
Technics Analyzer Aids Room Equalization E
The Technics SH-8000 audio-frequency analyzer enables users to adjust graphic equalizers to a specific listening environment. Using a warble tone as its signal source, the unit generates thirty-one tones over one-third-octave bands from 20 to 20,000 Hz. An easy-to-read precision sound-level meter has a switchable five-step sensitivity range (from 50 to 90 dB) and al lows accurate measurement of sound-pres sure level in I-dB steps from 35 to 105 dB.
To avoid tweeter overload or burnout, a protection switch prevents the unintentional generation of tones of 10 kHz or higher The unit comes with an omnidirectional back-electret, condenser-type measuring microphone calibrated for extremely flat response from 20 to 20,000 Hz and with a cord more than 13 feet long. The SH-8000 has a carrying case and is easily hooked into a sound system through an amplifier's auxiliary input jack.
Overall frequency response is 20 to 20,000 Hz ±2 dB. Frequency precision of the oscillator section is within ±6 percent.
The analyzer uses a 9-volt battery, the microphone a 1.5-volt battery. Dimensions of the analyzer are 8 1/2 x 2 1/2 x 43/4 inches; weight is 2 1/4 pounds. Price: $150.
Sennheiser's Ultralight "Inside-Out" Headphones
Sennheiser's new "Inside-Out" Model MS 100 stereo headphones are meant to be used with both personal portable stereo equipment and sophisticated home equipment. Not counting the cord, the headphones weigh under 1 1/2 ounces. The built in 4-foot steel-reinforced cable has a mini stereo phone plug, making the unit directly compatible with all personal portable equipment. A supplied 5-foot extension cable adapts the headphones for at-home listening. An extra pair of pads for the adjustable earpieces is included. Nominal impedance is 42 ohms. A 1-milliwatt input produces a nominal sound-pressure level of 96 dB. Frequency response is given as 20 to 20,000 Hz. Price: $85.
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Lower-Cost KEF Speakers
Various attributes of KEF's Reference Series of loudspeakers also appear in the company's new, less-expensive Standard Series. Vertical driver alignment, advanced driver materials, low-diffraction baffles, computer-designed cabinet bracing, newly developed bass-loading techniques, and sophisticated crossover networks are all used in the three speakers in the new series.
The largest system shown, the Carlton 111 (SP3020), is a two-way design with a passive bass radiator for reduced distortion at very low frequencies. The frequency range is given as 47 to 20.000 Hz ± 2.5 dB at 2 meters along the frontal reference axis. Directional characteristics are within 2 dB of the reference-axis response up to 20,000 Hz within ± 5' vertically and up to 10,000 Hz within ± 20' horizontally. Sensitivity of this 8-ohm speaker is 86 dB sound-pressure level (SPL) at 1 meter with a 1-watt in put. Minimum recommended amplifier power is 15 watts.
Dimensions: 27 1/2 x 12 3/8 x 11 inches. Weight: 26 1/4 pounds.
The smallest system shown, the Coda III (SP3011), is also a two-way design.
Its tweeter has a ferrofluid-cooled voice coil for increased reliability and power-handling capacity. Frequency range for the Coda 111 is given as 65 to 20,000 Hz ±3 dB. An 8-ohm system, the Coda 111 has a sensitivity of 87 dB SPL. Minimum amplifier power is 10 watts. It measures 18 1/2 x 11 x 8 1/2 inches and weighs 13 1/4 pounds.
The Carina II (SP3014) is also a two way system but has three drivers. The two low-frequency drivers provide improved power handling and increased efficiency. Frequency range is given as 60 to 20,000 Hz ±3 dB. Also an 8-ohm model, the Carina II's sensitivity is given as 89 dB SPL. Minimum recommended amplifier power is 10 watts.
Dimensions are 23 1/2 x 11 3/4 x 9 3/4 inches; weight is 20 1/2 pounds.
All three speakers are finished in simulated walnut and have removable brown textile grilles.
Prices per pair: Coda III, $300; Carina II, $500; Carlton III, $750.
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Three-Way Bozak Loudspeaker System
Bozak's LS-330A speaker system includes a 1-inch, wide-dispersion tweeter, a 6-inch Curvilinear aluminum-diaphragm midrange driver, and a 12-inch bass driver The midrange unit's diaphragm is said to operate virtually as a rigid disc, without the usual "cone break-up." The woofer has a pulp/lamb's-wool cone of varying density.
The speaker is protected by an incandescent-lamp limiter against tweeter damage from amplifier clipping and other dangerous signals. The crossover networks have 6-dB-per-octave rolloffs with crossover frequencies of 500 and 2,500 Hz. The hand-finished walnut-veneer cabinet is designed to be free from typical cabinet resonances Frequency response is given as 40 to 20,000 Hz ±3 dB. Nominal impedance is 8 ohms (6.5 ohms minimum). Sensitivity is 85 dB sound-pressure level with a 1-watt in put at 1 meter. Minimum recommended amplifier power is 25 watts. Dimensions arc 34 1/2 x 15 1/2 x 12 1/4 inches. Shipping weight is 64 1/2 pounds.
Price: $499. Bozak, Dept. SR, 68 Holmes Road, Newington, Conn 061111.
Microprocessor-Driven Technics Receiver
Technics' SA-410 Digital/Analog Computer-Drive receiver employs microprocessor technology to monitor signal conditions and heat-sink temperature changes on a dynamic basis and to adjust the output-transistor bias instantaneously to optimum levels. These features are claimed to minimize crossover distortion.
Most conventional stereo amplifiers, says Technics, utilize thermistors to monitor transistor temperatures and to alter the required bias-voltage levels to reduce signal distortion. Thermistors do not work instantaneously, however, because of thermal resistances between the power transistors and the thermistor. The effects of this do not show up in steady-state bench testing, ac cording to Technics, but can distort dynamic music reproduction. The microprocessor-drive system in the SA-410's push pull output circuitry is said to respond instantaneously.
Other features include sixteen station presets, both dial and numerical display of station frequency, connections and switching for two tape decks and two pairs of speakers, switchable infrasonic filter, sliding volume, bass, and treble controls, and a display for the Computer Drive circuitry.
Output power is specified as 45 watts per channel from 20 to 20,000 Hz with no more than 0.007 percent total harmonic distortion. Price: $300.
JVC Personal Portable Has Dolby-B, FM Tuner
JVC's CQ-F2K personal cassette player comes with a cassette-sized stereo FM tuner pack. Power is supplied to the tuner by the batteries of the CQ-F2K through a row of contacts on the tuner pack. The contacts also carry the headphone signals. The tuning dial can be turned through an opening in the player's cassette door. Dolby-B/ ANRS noise-reduction circuitry is included for correct playback of Dolby-B-encoded tapes. The unit's Metaperm head has a wide dynamic range to handle the higher-level signals that can be recorded on metal tape.
To reduce the problem of irregular tape movement, an anti-rolling mechanism using two vibration-canceling flywheels helps stabilize the tape transport. An electronically governed d.c. motor also contributes to the player's wow-and-flutter rating of 0.2 percent. There are cue-and-review facilities and a full auto-stop mechanism. The CQ F2 comes with shoulder and wrist straps and a belt clip. The supplied headphones weigh 9/to ounce. The player measures 31/4 x 53/s x 13/14 inches and weighs about 4/5 pound with batteries. Price: under $159.95.
VSP's MOSFET Power Amplifier
Said to combine the best of tube and solid-state design, the all-solid-state VSP Trans Mos power amplifier uses transconductance operation of its output stages the way most tube amplifiers do. The output stages-using MOSFET's for accurate wideband response, low distortion, and self-protecting operation-are claimed to be "optimally balanced" for instant, thump-less turn-on. A switchable infrasonic filter rolls off at 18 dB per octave. An r.f. filter pre vents interference. According to VSP, the Trans Mos is exceptionally stable with all loads, and its "Z" switch permits more efficient operation into lower impedances.
The Trans Mos is rated to deliver 150 watts per channel into 8-ohm loads from 20 to 20,000 Hz with total harmonic distortion of less than 0.05 percent. Headroom with 8-ohm loads is given as more than 2.8 dB.
Slew rate is greater than 70 volts per micro second. Maximum instantaneous output current is greater than 44 amperes. Dimensions are 5 x 15 x 14 inches. Weight is 40 flew Products pounds. The unit is rack-mountable with an optional mounting kit (RM-AM01). Price:
$825. VSP Labs, 670 Airport Boulevard.
Ann Arbor, Mich. 48104.
Lightweight, Low-Priced Koss Headphones
The Koss K-20 stereo headphone set is a non-sealing design with dynamic transducer elements and burgundy-colored foam ear cushions. It weighs 21/2 ounces (41/4 ounce, with its 8-foot Y-type cord). Frequency response is given as 18 to 20,000 Hz. Head phone impedance is 110 ohms; total harmonic distortion is rated at less than 1 percent. Price: $19.95.
Nakamichi's Plug-In Infrasonic Filters
The Nakamichi SF-10 Subsonic Filters have been designed to minimize infrasonic interference when making cassette recordings. The SF-10 consists of a pair of passive filters that plug directly into the left and right line-input terminals of a cassette deck or into the corresponding record outputs of a preamplifier, integrated amplifier, or receiver. They provide 10 dB of attenuation at 10 Hz (-3 dB at about 25 Hz). Nakamichi says that the filters can improve recording quality when taping from a source that contains substantial amounts of infrasonic energy, such as a warped phonograph record played with a tone-arm/cartridge system that resonates at too low a frequency. Such infrasonic energy can cause a wow-like sound in playback; under extreme conditions, it can even cause tape overload. Price: $15 per pair.
Full-Featured Jensen Car Power Amplifier
0 Delivering 15 watts per channel mini mum continuous average power into 4-ohm loads from 20 to 20,000 Hz with no more than 0.3 percent total harmonic distortion (or 40 watts per channel with 10 percent distortion), Jensen's A35 car stereo power amplifier features full electronic protection from thermal overload and reverse polarity.
In addition, the unit has high- and low-level inputs, short-circuit protection, and a fused power lead. Measuring about 5 x 3 x 2 inches, the amplifier is compatible with virtually any car stereo receiver or tape player.
Frequency response is 20 to 50,000 Hz ±3 dB. Signal-to-noise ratio is given as 80 dB.
Price: $74.95.
First Three-Way Advent Loudspeaker System
The Advent Model 6003 speaker system contains a 10-inch woofer, a 5-inch mid range driver, and a Direct Report dome tweeter. The midrange driver's diaphragm is made of a specially formulated polypropylene, and the combination dome/cone structure is said to provide a dome's excel lent dispersion in high frequencies together with a cone's ability to reproduce lower frequencies. The midrange unit has a 20-ounce magnet with a 2-inch high-temperature voice-coil assembly suspended in high-viscosity ferrofluid. The 6003's tweeter and woofer have been designed for improved power-handling capacity. The tapering of the front of the cabinet prevents sound reflection from cabinet edges, thus eliminating sound-wave aberrations, minimizing room and cabinet interference effects, and improving dispersion. The cabinet is finished in walnut veneer.
Sensitivity is given as 89 dB sound-pres sure level at 1 meter with a 1-watt drive level. Nominal impedance is 8 ohms. Frequency response is 39 to 22,000 Hz ± 2.5 dB.
Power-handling capacity is 150 watts continuous, 300 watts peak. Minimum recommended amplifier power is 10 watts. Total harmonic distortion is 0.5 percent above 50 Hz with a 1-watt drive level, 1 percent with a 10-watt input. Crossover frequencies are 750 and 4,500 Hz. Dimensions are 32 x 22 x 8 inches. Price: $379.95.
Budget-Priced dbx Noise-Reduction Unit
Using dbx's simultaneous encode/de code linear 2-to-1 companding process, the new NX-40 is said virtually to eliminate tape noise during recording while increasing dynamic range to as much as 110 dB.
While the NX-40 provides full decoded monitoring capability only with three-head recorders, it is also compatible with two- head tape decks. A front-panel switch turns the unit into a decoder for dbx-encoded discs. Frequency response is given as ± 1.5 dB from 50 to 15,000 Hz. Effective noise reduction is 30 dB. Harmonic distortion is less than 0.5 percent from 100 to 15,000 Hz, typically 0.1 percent at 1,000 Hz. Dynamic range is 88 dB (peak signal to weighted background noise). Input impedance is 50 kilohms; output impedance is 100 ohms.
Dimensions are 1 7/8 x 6 7/8 x 9 1/8 inches; weight is 3 pounds.
Price: $159.
NOTE: All product descriptions and specifications quoted in these columns are based on materials supplied by the manufacturers, who will respond directly to reader requests for further information.
Domestic inflation and fluctuations in the value of the dollar overseas affect the price of merchandise imported into this country.
Please be aware that prices quoted in this issue are therefore subject to change.
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