New Cassette Line From Century FD
-- Century FD, Inc. is introducing a new line of cassette tapes giving four choices of re cording times: the C-47, C-62, C-92, and C-122. All are ferric-oxide types using the "normal" bias and equalization settings.
Maximum output levels at 330 Hz (at 5 per cent distortion) are +9.5 dB for the C-47 and C-62 cassettes, +6.5 dB for the C-92, and +5 dB for the C-122. At 10,000 Hz the maximum output level is +2 dB for all four. Potential signal-to-noise ratios vary from 62 dB for the C-47 and C-62 cassettes to 57.5 dB for the C-122 cassettes. Third-harmonic distortion ratings vary from 0.3 per cent (C-47 and C-62) to 0.9 per cent (C-122). Century recommends that a recording level of +2 dB be used to exploit the rated dynamic-range advantages of the cassettes. Prices for the Century FD cassettes are $2.76 for the C-47, $2.96 for the C-62, $3.48 for the C-92, and $5.08 for the C-122.
BGW Amplifier Takes Electrostatic Phones
The Model 410, BGW's new stereo power amplifier, features fully modular construction (the electronic components for each channel are on single printed-circuit boards which can be "unplugged" for servicing) and has full complementary circuitry. Protection circuits prevent any d.c. voltage from reaching the loudspeakers; the response time of the protective relay is about 20 milliseconds. There is also a thermal-overload circuit. The front-panel output-power indicators consist of an array of LED's calibrated in watts and deci bels (average power). Readout sensitivity is adjustable, with settings of 0, -10, and -20 dB. Separate gain controls are provided for each channel; a speaker-selector switch and power switch round out the control complement. The 410 has a headphone jack for low-impedance dynamic phones and can be switched to drive electrostatic phones directly.
The 410 is rated at 200 watts per channel continuous power into 8 ohms. Frequency response is 20 to 20,000 Hz +0,-0.2 dB (3 to 100,000 Hz +0,-3 dB). Total harmonic distortion is 0.05 per cent or less; intermodulation distortion is 0.01 per cent. An input signal of 2 volts is required for rated power output.
Slew rate is 40 volts per microsecond, and rise time is 3 microseconds. The hum and noise level is-110 dB. Dimensions of the unit are 5 1/4 x 19 x 11 3/4 inches; a walnut-veneer cabinet is available as an option. Price: $699.
E1 Manufacturing Company announces its Sound Levels, which are loudspeaker stands, constructed of pine stock, in kit form. The structural members are pre-drilled to be bolted together by the kit builder. All necessary hardware (bolts, washers, and nuts) is provided. When fully assembled, the .Sound Levels provide a chair-like support-for a bookshelf-size speaker; the "seat" on which the speaker is placed can be set at a tilt of zero, 6 1/2, or 12 1/2 degrees from the horizontal. The rear of the speaker is supported by three uprights about 2 1/2 feet high. The Sound Levels raise the front of the speaker 8 to 10 inches from the floor. The pine structural members are finished with a walnut stain and a sealer. They are sold (in pairs) for about $40.
AKG's Low-cost, Non-isolating Headphone
The K-40 from AKG is an on-the-ear, non-isolating headphone intended to be an economy version of AKG's K-140. It is a dynamic phone which has a one-piece plastic headband with foam pads and ear cushions. The ear pieces can pivot about their mounts and can be moved vertically for adjustment. Frequency response is rated at 50 to 13,000 Hz, and the phones have a nominal impedance of 200 ohms. They can be driven to a sound-pressure level of 94 dB with a 0.45-volt input and 112 dB with 3.6 volts. Maximum continuous out put is 117 dB (with an input of 6.3 volts). The K-40 headphones weigh 6 ounces and are sup plied with a 3-meter (about 10 feet) cable. Price: $19.50.
New Impulse-noise Suppressor from Garrard
Garrard has entered into noise reduction with the new MRM 101 Music Recovery Module, an impulse-noise-suppression device.
The MRM 101 is actually a phono preamplifier with click- and pop-suppressing circuitry; its outputs are fed to the "auxiliary" inputs of a regular preamplifier. It has a moderate-gain preamp that boosts the level of the signals arriving from the cartridge. Following voltage amplification, the signal is split in two; half is passed on to an electronic time-delay circuit, the other half is sent to a detector that senses the presence of a noise impulse.
Detection is based on the rise time, fall time, and duration of this kind of noise. If a click or pop is detected, the output of the MRM 101 is reduced in the time-delayed path to a level 30 dB below the average program level for the duration of the noise signal. During this time interval (amounting to less than 2.7 milliseconds) there is actually a gap in the program. However, the attenuation is not sharp but gradual (it takes from 1/2 to 4 millisecond for the level to drop to-30 dB), thus preventing an audible "hole" in the program.
Following the detection circuitry is an out put-gain stage that boosts the signal voltage to drive the auxiliary inputs of the system preamp. The degree of suppression can be set for best audible results by the user. A LED on the front panel glows whenever the MRM 101's suppression circuitry acts. There is a switch to defeat the impulse-noise reduction system so that the unit may be used as a pho no preamp only. Another LED indicates when the suppression circuitry is in the signal path.
The nominal output of the MRM 101 is 300 millivolts, and rated output (at 1 per cent distortion) is 2.5 volts with the suppression circuits engaged. At typical levels distortion is 0.01 per cent without and 0.1 per cent with the suppression circuitry. Channel balance is better than 2 dB. Signal-to-noise ratios are 100 dB without and 85 dB with the suppression circuitry engaged. Input impedance is 47,000 ohms. The MRM 101 has approximate dimensions of 2 3/4 x 15 x 12 inches. Price: about $200.
CM Laboratories' Active Crossover
CM Laboratories' model 604 Stereo Electronic Crossover is a device used in biamplified stereo systems and commercial sound-reinforcement applications. The 604 provides switchable crossover points, at intervals of 100 Hz, from 100 Hz to 12,700 Hz as well as level controls for the high-frequency and low-frequency outputs. An additional crossover point of 60 Hz is included for use with one or two subwoofers. The low-pass outputs include regular stereo outputs as well as mono outputs with the sum (left plus right) and difference (left minus right) signals of the two stereo channels. This permits the 604 to be used with a single subwoofer and for bridging two power amplifiers.
Frequency response of the 604 is flat within 3 dB from the selected frequency to 100,000 Hz for the high-pass section and from 3 Hz to the selected frequency for the low-pass section. Crossover slopes are all 12 dB per octave. Rated output is 2 volts rms into a high-impedance load (10,000 to 50,000 ohms) and 1 volt into a 600-ohm load. Clipping output is 10 volts (high-impedance load). Both total harmonic and intermodulation distortion are un der 0.05 per cent at rated output, and the signal-to-noise ratio is over 90 dB. Dimensions are 13/4 x 19 x 6 inches; the unit is suitable for rack mounting. Weight is 4 pounds. Price: un der $200.
Hand-held Spectrum Analyzer from Ivie
Ivie Electronics' IE-10A Audio Spectrum Analyzer is an extremely compact test instrument that can be used as an octave spectrum analyzer, sound-level meter, and precision preamplifier for microphone inputs. The panel of the IE-10A has a matrix of 160 red LED's that displays the average sound level of each of the ten standard octaves within the audio-frequency range. The result is a graphic display of the amplitude-vs.-frequency characteristic of any sound source picked up by the IE-10A's built-in omnidirectional micro phone. The IE-10A can also be switched to operate as a sound-pressure-level meter (using its built-in microphone) with A or C weighting. It is calibrated in both sound-pressure-level (SPL) decibels and dBm. The display has an overall range of 24 to 149 dB SPL in 3-dB steps, with the scale resolution adjustable for 1- , 2- , or 3-dB steps. The IE-10A also accepts external electrical inputs through a phono jack and will display equalization curves when pink-noise test signals are used.
The horizontal scale of the display is labeled with the centering frequencies of the ten ANSI-standard octaves covered, which are 32, 63, 125, 250, 500, 1,000, 2,000, 4,000, 8,000, and 16,000 Hz. An output jack is pro vided for directing the signal being tested to other processing equipment. The IE-10A runs on built-in rechargeable batteries and has a LED that glows when they need charging.
The response of the IE-10A's microphone and preamp is flat within 2 dB from 20 to 20,000 Hz and from 0 to 90 degrees off-axis.
The preamp offers up to 80 dB of gain and accepts a wide range of input voltages: the maximum input level is 1,000 volts a.c. :4:100 volts d.c. Total harmonic distortion in the preamp is 0.1 per cent for a 2-volt input. Input impedance is 100,000 ohms, and if used separately the preamp will drive load impedances of 600 ohms or higher. The IE-10A is provided with an a.c. adapter/charger and can operate continuously for about 2 hours between charges; the charging time is about 3 hours.
The unit has approximate dimensions of only 6 x 2 3/4 x 1 3/4 inches, and it comes with a vinyl carrying case and patch cords. Price: $595.
A variety of miniaturized accessories are avail able, including a pink-noise generator and a distortion analyzer.
The Nakamichi 430 Stereo FM tuner is a new addition to that company's line, with a size and style to match the Model 410 preamplifier and the 420 power amplifier. Its low-profile front panel, finished in black, has a lighted dial pointer, a tuning lamp, and a LED for indicating the reception of stereo broad casts. The tuning lamp lights up when the received signal's strength is enough for 50 dB of quieting. When the dial pointer is at the center of the desired channel, the two green strips on either side of the pointer light simultaneously.
The tuner has selectable "normal" (wide) and narrow i.f. bandwidths as well as provision for an optional Dolby decoder (the decoder is available in the form of a plug-in card). There is a "hi-blend" switch that reduces channel separation at higher frequencies, thus improving the signal-to-noise ratio on weak stations.
The 430 has special multipath output jacks that can be connected to the horizontal and vertical inputs of an oscilloscope to monitor the amount of multipath distortion in the received signal.
The 430 has a usable sensitivity of 1.8 microvolts (RV) in mono, equivalent to 10.5 dBf. The 50-dB quieting sensitivity is 4µV (17.3 dBf) in mono and 40 uV (37.3 dBf) in stereo. The capture ratios are 1.5 and 4 dB in the normal and narrow i.f. modes, respectively. Alternate-channel selectivity is over 60 dB in the normal mode and over 90 dB in the narrow mode. Spurious response, image, and i.f. rejection are all better than 100 dB, and AM suppression is over 60 dB. The output level of the 430 (at 50 percent modulation) is 0.5 volt; distortion is under 0.06 percent in mono and 0.09 per cent in stereo in the normal mode, and under 0.2 per cent in mono and 0.4 per cent in stereo in the narrow mode. Stereo separation is over 35 dB (normal) and 30 dB (narrow) at 10,000 Hz, and over 50 dB (normal) and 30 dB (narrow) at 1,000 Hz (referring to 100 per cent modulation of a 65-dBf input).
Ultimate signal-to-noise ratios are over 70 dB in mono and 68 dB in stereo.
The 430 has approximate dimensions of 3 1/4 x 15 3/4 x 8 3/4 inches and weighs about II pounds. Price: $400.
The model DB-100 plug in Dolby FM adapter is priced at $40. An optional walnut cabinet is $30.
Sinus: Swedish Loudspeaker Line
Sinus is a Swedish loudspeaker manufacturer now introducing its product line in the United States. The line consists of two acoustic-suspension models, the 2300 and 3400, and two bass-reflex models, the 44F and 55M (shown). The 2300 has a 9-inch woofer and 1-inch dome tweeter crossed over at 4,000 Hz, and the 3400 is a three-way system employing a 10.7-inch woofer, 3.35-inch mid-range, and 0.75-inch tweeter with crossover points of 700 and 6,000 Hz. The 44F has a 10.7-inch woofer, 3.35-inch mid-range, and 1-inch dome tweeter; crossover points are 700 and 6,000 Hz.
The top-of-the-line speaker is the 55M, which has two 10.7-inch woofers, a 1.8-inch dome mid-range, and two 0.75-inch dome tweeters. The crossover points are 600 and 7,000 Hz, with slopes of 18 dB per octave.
The two woofers are mounted in a special cast aluminum "tunnel" and both radiate forward.
A polyester filter is placed between them in the duct. The two tweeters and the mid-range all radiate from the front of the enclosure and are mounted in a horizontal line. Level controls are provided for the mid-range and tweeter in the form of a single switch with four settings: normal, 5-dB tweeter boost, 5-dB mid-range boost, and simultaneous 5-dB boost for both. Anechoic frequency response is 30 to 18,000 Hz. Maximum continuous input power is 90 watts per channel and peak program-power input is 140 watts. Impedance is a nominal 4 ohms. The 55M has approximate dimensions of 24 1/2 x 13 x 18 inches and weighs 58 1/2 pounds. It is sold in matching pairs (the left speaker has the mid-range mounted on the left of the baffle).
Price: about $1,300 per pair. Prices of the other speakers in the Sinus line are: about $160 for the 2300, $300 for the 3400, and $450 for the 44F.
Marantz's New "High Definition" Speakers
The HD line of loudspeaker systems from Marantz features five models: the HD-880, 770, 660, 550, and 440. The top-of-the-line HD-880 (shown) has a 12-inch woofer, 5-inch mid-range, 11/2-inch dome tweeter, and 1-inch "super-tweeter." The enclosure is nominally an infinite baffle, but it has a tuned port sealed with a removable plug; removal of the plug vents the system and provides a 3 or 4 dB boost in the 30- to 75-Hz region. This feature, referred to as "Vari-Q" by Marantz, is offered on all the systems in the HD line with the exception of the low-end HD-440. The HD-880 has level controls for mid-range, tweeter, and super-tweeter; the drivers are crossed over at 750, 2,300, and 5,000 Hz. The HD-770 has- the same driver complement as the 880 but a smaller enclosure; the HD-660 and 550 are without the I-inch super-tweeter and have 10- and 8-inch woofers, respectively. The HD-440 has an-8-inch woofer and two 3 1/2-inch cone drivers, one employed for mid frequencies-and the other as a tweeter.
Key specifications of the HD-880 include a frequency response of 30 to 22,000 Hz ±3 dB and a power-handling capacity of 150 watts on program material. Impedance is nominally 8 ohms. Response at 45 degrees off-axis is down 4.8 dB at 15,000 Hz and down 2 dB at 5,000 Hz. The HD-880 produces a sound-pressure level of 90 dB with a 1-watt input at I meter. The speaker's dimensions are 40 1/4 x 16 x 12 inches. Price: about $320. Other HD speakers range from about $260 for the HD-770 to about $90 for the HD-440.
Audio Interference Pamphlet Covers Problems and Cures
Electronic Specialists, Inc. is offering a new pamphlet that describes. interference problems common in audio equipment and suggests cures. The pamphlet covers all types of a.c.-line interference, such as that due to lightning and appliances. It also discusses a variety of radio-frequency interference (RFI) problems, such as the pick-up of citizens-band and other radio transmissions by the speaker or phono cables in hi-fi systems. The pamphlet, which consists of two double-size pages and includes several practical examples of the phenomena discussed, is available free (include a stamped self-addressed envelope) from Electronic Specialists, Box 122, Natick, Massachusetts 01760. Electronic Specialists manufactures a variety of electronic filter products, a number of which have applications in audio, such as a.c.-line, FM-input, and speaker-line filters.
NOTICE: M product descriptions and specifications quoted in these columns are based-on materials sup plied by the manufacturer.
Recent fluctuations in the value of the dollar will have an effect on the price of merchandise imported into this country. Please be aware that the prices quoted in this issue may be subject to change.
Also see:
EDITORIALLY SPEAKING, by WILLIAM ANDERSON
BEST RECORDINGS OF THE PAST TWENTY YEARS: Our reviewing panel selects the best recordings of the past twenty years
Source: Stereo Review (USA magazine)