A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. It was long believed to be invented by US engineer Edwin Armstrong, but after some controversy the patent is now credited to French radio engineer and radio manufacturer Lucien Lèvy. Virtually all modern radio receivers use the superheterodyne principle.
A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. Tesla experimented with a number of different configurations consisting of two, or sometimes three, coupled resonant electric circuits.
Mark Levinson is an American high-end audio equipment brand established in 1972 by eponymous founder Mark Levinson, and based in Stamford, Connecticut. It is owned by Harman International Industries, a subsidiary of South Korean company Samsung Electronics.
The Williamson amplifier is a four-stage, push-pull, Class A triode-output valve audio power amplifier designed by D. T. N. Williamson during World War II. The original circuit, published in 1947 and addressed to the worldwide do it yourself community, set the standard of high fidelity sound reproduction and served a benchmark or reference amplifier design throughout the 1950s. The original circuit was copied by hundreds of thousands amateurs worldwide. It was an absolute favourite on the DIY scene of the 1950s, and in the beginning of the decade also dominated British and North American markets for factory-assembled amplifiers.
Mesa/Boogie is an American company in Petaluma, California, that manufactures amplifiers for guitars and basses. It has been in operation since 1969.
The Mark Levinson No. 26S Dual Monaural Preamplifiers used Teflon circuit boards to supposedly differentiate the No. 26 and the 26S models, produced between 1991 and 1994 by Madrigal Audio Laboratories. This unit utilizes Camac coaxial connectors, which were used in the medical industry as well, because they break hot before they break ground when unplugged. No shorting electronics means a safe preamp and safe ER patients. An external power block, the PLS-226, was used to keep interference to a minimum.
A headphone amplifier is a low-powered audio amplifier designed particularly to drive headphones worn on or in the ears, instead of loudspeakers in speaker enclosures. Most commonly, headphone amplifiers are found embedded in electronic devices that have a headphone jack, such as integrated amplifiers, portable music players, and televisions. However, standalone units are used, especially in audiophile markets and in professional audio applications, such as music studios. Headphone amplifiers are available in consumer-grade models used by hi-fi enthusiasts and audiophiles and professional audio models, which are used in recording studios.
Multiple electronic amplifiers can be connected such that they drive a single floating load (bridge) or a single common load (parallel), to increase the amount of power available in different situations. This is commonly encountered in audio applications.
An H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards.
A test probe is a physical device used to connect electronic test equipment to a device under test (DUT). Test probes range from very simple, robust devices to complex probes that are sophisticated, expensive, and fragile. Specific types include test prods, oscilloscope probes and current probes. A test probe is often supplied as a test lead, which includes the probe, cable and terminating connector.
The Fender Twin and Twin Reverb are guitar amplifiers made by Fender Musical Instruments Corporation. The Twin was introduced in 1952, two years before Fender began selling Stratocaster electric guitars. The amps are known for their characteristically clean tone.
Optonica was a subdivision of Japanese electronics manufacturer Sharp that made high end hi-fi products systems.
A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.
Constant-voltage speaker systems refer to networks of loudspeakers which are connected to an audio amplifier using step-up and step-down transformers to simplify impedance calculations and to minimize power loss over the speaker cables. They are more appropriately called high-voltage audio distribution systems. The voltage is constant only in the sense that at full power, the voltage in the system does not depend on the number of speakers driven. Constant-voltage speaker systems are also commonly referred to as 25-, 70-, 70.7-, or 100-volt speaker systems; distributed speaker systems; or high-impedance speaker systems. In Canada and the US, they are most commonly referred to as 70-volt speakers. In Europe, the 100 V system is the most widespread, with amplifier and speaker products being simply labeled with 100 V.
Circlotron valve amplifier is a type of power amplifier utilizing symmetrical cathode-coupled bridge layout of the output stage. Original circlotrons of 1950s used output transformers to couple relatively high output impedance of vacuum tubes to low-impedance loudspeakers. Circlotron architecture, easily scalable, was eventually adapted to operate without output transformers, and present-day commercially produced circlotron models are of output transformerless (OTL) type.
The TRM-800 was a Hi-End solid state integrated stereo amplifier made in Japan, using NEC power transistors, by Nikko. It was the top of the line model in the Nikko amplifier range of TRM's series; beautifully housed in a wooden walnut-finished cabinet and a handsome brushed aluminum front panel, was introduced in 1975 the same year as the Marantz 2235. It was a 2 channel amp; however, it had three sets of speaker connections; those powered selected by buttons. At 8 ohms, the amp could put out 65 Watts per channel RMS, delivering superb high fidelity sound with exceptional tone quality. Unlike many amps of this time, however, the TRM-800 was stable at lower impedances than 8 ohms; down to 4 ohms. The TRM-800's frequency response ranges 10Hz to 40.000 Hz ±1 dB with T.H.D. less than 0.1% at rated output. Its preamplifier and main amplifier were separable for multi-channel amplifier systems. The amp has internal circuit breakers which prevent it from clipping or overheating. Its power consumption is 250 watts. For equalization it has only a bass and a treble knob; however the frequency of these are selectable; between 250 and 500 Hertz for the bass, and between 2.5 and 5 kHz for the treble. It also has a high, low, and a subsonic filter. There are two excellent phono stages; phono 2 is provided with impedance matching selection, for using different types of cartridges (MC/MM).
.
The NAD 3020 is a stereo integrated amplifier by NAD Electronics, considered to be one of the most important components in the history of high fidelity audio. Launched in 1978, this highly affordable product delivered a good quality sound, which acquired a reputation as an audiophile amplifier of exceptional value. By 1998, the NAD 3020 had become the most well known and best-selling audio amplifier in history.
The Pioneer SX-1980 was a radio receiver that Pioneer Corporation introduced in 1978, to be matched with the HPM series of speakers. It is rated at a staggering 270 watts per channel into 8 ohms. However, in the September 1978 issue of Audio Magazine, Leonard Feldman did a spec test on the SX-1980 and concluded that the rating of 270 watts per channel was too conservative. He stated in his report:
Though the new [IHF mandated] "Dynamic Headroom" measurement is specified in dB, it should be mentioned that based upon the short-term signal used to measure the 2.3 dB headroom of this amplifier, it was producing nearly 460 watts of short-term power under these test conditions!
The NE5532, also sold as SA5532, SE5532 and NG5532 is a dual monolithic, bipolar, internally compensated operational amplifier for audio applications introduced by Signetics in 1979. The 5532 and the contemporary TL072 were the first operational amplifiers that outperformed discrete class A circuits in professional audio applications. Due to low noise and very low distortion, the 5532 became the industry standard for professional audio. According to Douglas Self, "there is probably no music on the planet that has not passed through a hundred or more 5532s on its way to the consumer". The performance of the 5532 remained best in class for almost thirty years, until the introduction of the LM4562 in 2007. As of 2021, the 5532 remains in mass production as a generic product.
