Bob Carver

Last updated June 25, 2023

Robert W. (Bob) Carver is an American designer of audio equipment based in the Pacific Northwest.

Educated as a physicist and engineer, he found an interest in audio equipment at a young age. He applied his talent to produce numerous innovative high fidelity designs since the 1970s.^[1] He is known for designing the Phase Linear 700, at 350 W per channel the most powerful consumer audio amplifier available in 1972. He went on to found the Carver Corporation in 1979, Sunfire in 1994, and the Bob Carver LLC in 2011 ^[2] which was sold to Jade Design in June, 2013.^[3] However, in December 2013, Bob Carver and Jade Design parted ways.^[4]

Amplifier modeling

Carver caused a stir in the industry in the mid-1980s when he challenged two high-end audio magazines to give him any audio amplifier at any price, and he'd duplicate its sound in one of his lower cost (and usually much more powerful) designs. Two magazines accepted the challenge.

First, The Audio Critic chose a Mark Levinson ML-2 which Bob acoustically copied (transfer function duplication) and sold as his M1.5t amplifier (the “t” stood for transfer function modified).

In 1985, Stereophile magazine challenged Bob to copy a Conrad-Johnson Premier Four (the make and model was not named then, but revealed later) amplifier at their offices in New Mexico within 48 hours. The Conrad Johnson amplifiers were one of the most highly regarded amplifiers of the day, costing in excess of $6,000 a pair.

In both cases, the challenging amplifier could only be treated as a “black box” and could not even have its lid removed. Nevertheless, Carver, used null difference testing, (null difference testing consists of driving two different amplifiers with identical signal sources and exact levels, but out of phase by exactly 180 degrees. If the amplifiers were 100% identical, no sound would be heard. If sound was heard, the audio amps had different properties). Bob Carver used "distortion pots" to introduce amplifier characteristics, fine-tuned to null-out any sound differences. His modified amplifier sound was so similar, Stereophile Magazine editors could not tell the difference between his amplifier and one costing more than $6,000.^[5] This amplifier was marketed as the M1.0t for about $400.00. Carver successfully copied the sound of the target amplifier and won the challenge. The Stereophile employees failed to tell the difference in their own listening room.^[5] He marketed “t” versions of his amplifiers incorporating the sound of the Mark Levinson and Conrad Johnson designs which caused him some criticism. In light of this criticism, Carver went on to design the Silver Seven, the most expensive and esoteric conventional amplifier up to that time and duplicated its sound in his M 4.0t and later models which sold for some 1/40th the price (around $600–$1500).

This also started Carver's departure from the M-series amplifier to the more robust and current-pushing TFM series amplifiers. The TFM amplifiers were designed specifically to drive the demanding load of the Amazing ribbon loudspeakers. The apex of Carver's amplifier line was the Lightstar, which is now a collectors' item. Only approximately 100 of the amplifiers were made. The original Lightstar amplifier, called the Lightstar Reference, featured a dual-monoblock design, with separate power cords for each channel. A later version, called the Lightstar 2.0, featured one power cord & other cost-saving measures to shave approximately $1800 off the retail price. The two are reported to be sonically identical.

Carver also later sued Stereophile magazine for its alleged bias against Carver products. (Stereophile had first filed suit against Carver for reprinting the magazine's copyrighted material without authorization.) The case was arbitrated with neither side awarded damages.

Product naming

Carver has used some names in marketing which have other technical definitions:

The "auto-correlator" is a multi-band, single-ended dynamic noise filter, as described in U.S. Patent 3,989,897 . The Phase Linear 1000 audio processor, and the Model 4000 preamplifier, which incorporate the same circuitry, have noise reduction in four frequency bands, one in the bass intended to suppress turntable rumble and three in the treble intended to suppress tape hiss and such. The noise filters are controlled by signals derived from bandpass filters, not from a correlation process. Correlation is the comparison of two or more signals, while auto-correlation is the comparison of a signal with delayed versions of itself to determine the degree of similarity at different delay times — useful, for example, to determine the amount of delay that produced an echo.
"Magnetic field coil power amplifier" — audio amplifiers of the vacuum-tube era used transformers, incorporating coils of wire, to convert the high-voltage, low-current output of the output tubes to a low-voltage, high-current output suitable for loudspeakers. Output transformers are no longer necessary with amplifiers, including Carver's, that use transistors. Carver's U.S. Patent 4,218,660 , first applied in his model M400 power amplifier, describes a power supply whose input switches on and off at an ultrasonic rate to adapt to the varying power demand of the amplifier. The innovation is in the power supply, not the amplification circuitry, and in the use of switching, not in the use of a coil or coils.
"Sonic holography", as described in U.S. Patent 4,218,585 was first incorporated in the Carver C4000 preamplifier. It enhances stereo imaging by introducing a delayed and equalized signal from the right channel at the left loudspeaker to cancel the signal from the right loudspeaker at the listener's left ear (and vice versa).
The "asymmetrical charge-coupled detector" is not the FM detector circuit of tuners, but rather, as described in U.S. Patent 4,457,012 , it is single-ended dynamic noise-reduction processing applied to the noisy left-minus-right component of a weak FM-stereo signal, along with artificial ambiance generation to compensate for loss of ambiance resulting from the noise reduction. This innovation was introduced in the Carver TX-1-11 component FM stereo tuner noise reduction unit and the Carver TX-11 AM/FM Stereo Tuner in 1982.
Sunfire Corporation:

The creation of the perfect solid-state amplifier:

1) Full output current from each transistor is always available up to 20 amperes per transistor.

2) Massive output current is available even at low output impedances.

3) Heat sinks are not required.

4) Power continuously doubles down to below 1 ohm.

5) Most of the input power goes to the load, therefore, the power supply can weigh 30 pounds instead of 80 pounds. The amplifier can supply humongous current, massive output power, tremendous voltage, runs cool, and is efficient.

6) Only 12 output transistors are needed per channel for a peak-to-peak current of 240 amps.

7) Bias current and idling current issues become irrelevant and nonproblematic.

8) The Tracking Downconverter multiplies current in the same ratio that the output voltage is reduced and it does so automatically by its intrinsic nature.

9) At high impedances, it delivers high voltage and high current. At low impedances or difficult impedances, it delivers even more current, delivering awesome and difficult to believe amounts.

10) When biwired, Sunfire delivers incredible bass whack and a huge three dimensional sound stage with detail retrieval so stunning that you will often hear musicians breathing.

Pictures

Carver TFM-6cb, TFM-15CB, TFM-55x, CT-27v
Carver M-500t and M-1.0t mk II modified

Related Research Articles

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.

A microphone, colloquially called mic or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers for recording voice, speech recognition, VoIP, and for other purposes such as ultrasonic sensors or knock sensors.

Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the speakers in place. Another type, known as earbuds or earpieces consist of individual units that plug into the user's ear canal. A third type are bone conduction headphones, which typically wrap around the back of the head and rest in front of the ear canal, leaving the ear canal open. In the context of telecommunication, a headset is a combination of headphone and microphone.

Balanced audio is a method of interconnecting audio equipment using balanced interfaces. This type of connection is very important in sound recording and production because it allows the use of long cables while reducing susceptibility to external noise caused by electromagnetic interference. The balanced interface guarantees that induced noise appears as common-mode voltages at the receiver which can be rejected by a differential device.

A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the 1960s and 1970s. Valve amplifiers can be used for applications such as guitar amplifiers, satellite transponders such as DirecTV and GPS, high quality stereo amplifiers, military applications and very high power radio and UHF television transmitters.

<span class="mw-page-title-main">Preamplifier</span> Electronic amplifier that converts weak signal into strong signal

A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier and a loudspeaker. Without this, the final signal would be noisy or distorted. They are typically used to amplify signals from analog sensors such as microphones and pickups. Because of this, the preamplifier is often placed close to the sensor to reduce the effects of noise and interference.

<span class="mw-page-title-main">Damping factor</span>

In an audio system, the damping factor gives the ratio of the rated impedance of the loudspeaker to the source impedance of the power amplifier. Only the magnitude of the loudspeaker impedance is used, and the power amplifier output impedance is assumed to be totally resistive.

Line level is the specified strength of an audio signal used to transmit analog audio between components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles.

PS Audio is an American company specializing in high-fidelity audio components equipment for audiophiles and the sound recording industry. It currently produces audio amplifiers, preamplifiers, power related products, digital-to-analog converters, streaming audio, music management software and cables.

<span class="mw-page-title-main">Pickup (music technology)</span> Transducer that senses vibration of musical instruments

A pickup is a transducer that captures or senses mechanical vibrations produced by musical instruments, particularly stringed instruments such as the electric guitar, and converts these to an electrical signal that is amplified using an instrument amplifier to produce musical sounds through a loudspeaker in a speaker enclosure. The signal from a pickup can also be recorded directly.

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.

The chief electrical characteristic of a dynamic loudspeaker's driver is its electrical impedance as a function of frequency. It can be visualized by plotting it as a graph, called the impedance curve.

The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony, this undulating current is directly passed through the telephone wires to the central office. In public address systems it is amplified by an audio amplifier. The frequency response of most carbon microphones, however, are limited to a narrow range, and the device produces significant electrical noise.

A valve RF amplifier or tube amplifier (U.S.) is a device for electrically amplifying the power of an electrical radio frequency signal.

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.

Technical specifications and detailed information on the valve audio amplifier, including its development history.

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.

<span class="mw-page-title-main">Tube sound</span> Characteristic quality of sounds from vacuum tube amplifiers

Tube sound is the characteristic sound associated with a vacuum tube amplifier, a vacuum tube-based audio amplifier. At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable methods were not known or used. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. However, solid state amplifiers have been developed to be flawless and the sound is later regarded neutral compared to tube amplifiers. Thus the tube sound now means 'euphonic distortion.' The audible significance of tube amplification on audio signals is a subject of continuing debate among audio enthusiasts.

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.

References

The information on Carver products comes from Carver product brochures and manuals. Carver's career has been extensively covered by audio industry magazines including Stereophile, Audio, High Fidelity , and Stereo Review .

↑ International competitiveness in electronics. DIANE Publishing. 1983. pp. 520–. ISBN 978-1-4289-2396-6.
↑ Bob Carver: Carving a Name For Himself. Stereophile magazine, 7 February 1990. Retrieved 5 July 2011.
↑ Jade Design Acquires Bob Carver, LLC Stereophile magazine, Posted: Jun 19, 2013. Retrieved 5 April 2014.
↑ Emotiva and Bob Carver Part Ways. ThePoorAudiophile. Posted: December 14, 2013
1 2 Holt, J. Gordon (2009-05-11). "The Carver Challenge". Stereophile.com. Archived from the original on 2010-11-30. Retrieved 2020-08-07.

External links

Patents

U.S. Patent 3,727,148 Amplifier with Protective Energy Limiter Circuit Components, filed January 1972, issued April 1973
U.S. Patent 3,989,897 Method and Apparatus for Reducing Noise Content in Audio Signals, filed October 1974, issued November 1976 (auto-correlator noise reduction)
U.S. Patent 4,218,585 Dimensional Sound Producing Apparatus and Method, filed April 1979, issued August 1980 (sonic holography)
U.S. Patent 4,218,660 Audio Amplifier and Method of Operating Same, filed November 1978, issued August 1980 (magnetic field coil power amplifier)
U.S. Patent 4,309,570 Dimensional Sound Recording and Apparatus and Method for Producing the Same, filed April 1979, issued January 1982
U.S. Patent 4,415,768 Tuning Apparatus and Method, filed May 1981, issued November 1983
U.S. Patent 4,445,095 Audio Amplifier, filed February 1982, issued April 1984
U.S. Patent 4,457,012 FM Stereo Apparatus and Method, filed June 1982, issued June 1984 (asymmetrical charge coupled stereo detector)
U.S. Patent 4,484,150 High Efficiency, Light Weight Audio Amplifier and Power Supply, filed September 1982, issued November 1984
U.S. Patent 4,586,002 Audio Amplifying Apparatus and Method, filed June 1984, issued April 1986
U.S. Patent 4,808,946 Lightweight, High Power Audio Amplifier and Power Supply, filed December 1986, issued February 1989
U.S. Patent 4,815,141 Apparatus and Methods for Removing Unwanted Components from a Communications Signal, filed December 1986, issued March 1989
U.S. Patent 5,748,753 High Power Audio Subwoofer, filed January 1996, issued May 1998
U.S. Patent 5,937,074 High Back EMF, High Pressure Subwoofer, filed August 1997, issued August 1999
U.S. Patent 6,166,605 Integrated Audio Amplifier, filed September 1998, issued December 2000

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[1] International competitiveness in electronics. DIANE Publishing. 1983. pp. 520–. ISBN 978-1-4289-2396-6.

[2] Bob Carver: Carving a Name For Himself. Stereophile magazine, 7 February 1990. Retrieved 5 July 2011.

[3] Jade Design Acquires Bob Carver, LLC Stereophile magazine, Posted: Jun 19, 2013. Retrieved 5 April 2014.

[4] Emotiva and Bob Carver Part Ways. ThePoorAudiophile. Posted: December 14, 2013

[:0-5] 1 2 Holt, J. Gordon (2009-05-11). "The Carver Challenge". Stereophile.com. Archived from the original on 2010-11-30. Retrieved 2020-08-07.

[1]

[2]

[3]

[4]

[5]