Bob Carver
Encyclopedia
Robert W. 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 very young age. He applied his talent to produce numerous innovative high fidelity
designs since the 1970s. 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 and Sunfire in 1994.
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 Five (the make and model was not named in the challenge but revealed later) amplifier at their offices in New Mexico
within 48 hours. The Conrad Johnson amplifier was one of the most highly regarded amplifiers of its day, costing in excess of $12,000.
Of note that in both cases, the challenging amplifier could only be treated as a “black box” and could not even have its lid removed. Nevertheless, Carver, using null difference testing, successfully copied the sound of the target amplifier and won the challenge. The Stereophile employees failed to pass a single blind test with their own equipment, and in their own listening room. He marketed “t” versions of his amplifiers incorporating the sound of the Mark Levinson and Conrad Johnson designs which caused him some criticism by those who failed to understand the true nature of the challenge — that it was possible to duplicate an audio amplifier's sound in two completely dissimilar designs. In light of this criticism, Bob 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.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
designer of audio equipment based in the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
.
Educated as a physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
and engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
, he found an interest in audio equipment at a very young age. He applied his talent to produce numerous innovative high fidelity
High fidelity
High fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
designs since the 1970s. He is known for designing the Phase Linear
Phase Linear
Phase Linear was an audio equipment manufacturer founded by Bob Carver in 1970. While primarily known as a power amplifier company it also produced several innovative preamplifers, tuners and the Andromeda loudspeaker.-History:...
700, at 350 W
Audio power
Audio power is the electrical power transferred from an audio amplifier to a loudspeaker, measured in watts. The electrical power delivered to the loudspeaker, together with its sensitivity, determines the sound power level generated .Amplifiers are limited in the electrical energy they can...
per channel the most powerful consumer audio amplifier
Audio amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification,...
available in 1972. He went on to found the Carver Corporation in 1979 and Sunfire in 1994.
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 took him up on the challenge.First, The Audio Critic chose a Mark Levinson
Mark Levinson
The company Mark Levinson, now owned by Madrigal Audio Laboratories specializes in high-end digital audio processors, integrated amplifiers, power amplifiers, pre amplifiers, and CD players...
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
Stereophile
Stereophile is a monthly magazine that focuses on high end audio equipment, such as loudspeakers and amplifiers, and audio-related news, such as online audio streaming. It was founded in 1962 by J. Gordon Holt....
magazine challenged Bob to copy a Conrad-Johnson Premier Five (the make and model was not named in the challenge but revealed later) amplifier at their offices in New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
within 48 hours. The Conrad Johnson amplifier was one of the most highly regarded amplifiers of its day, costing in excess of $12,000.
Of note that in both cases, the challenging amplifier could only be treated as a “black box” and could not even have its lid removed. Nevertheless, Carver, using null difference testing, successfully copied the sound of the target amplifier and won the challenge. The Stereophile employees failed to pass a single blind test with their own equipment, and in their own listening room. He marketed “t” versions of his amplifiers incorporating the sound of the Mark Levinson and Conrad Johnson designs which caused him some criticism by those who failed to understand the true nature of the challenge — that it was possible to duplicate an audio amplifier's sound in two completely dissimilar designs. In light of this criticism, Bob 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 which have clearly defined technical meanings so oddly unrelated to his products' actual design and function as to be merely amusing rather than deceptive.- "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 (see below) 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.
- The "auto-correlator" is a multi-band, single-ended dynamic noise filter, as described in U.S. patent 3,989,897 (see below). The Phase Linear 1000, and the Model 4000 preamplifier, which incorporates 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 the like. 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.
- "Sonic holography", as described in U.S. Patent 4,218,585 (see below), is the enhancement of 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 Carver's tuners, but rather, as described in U.S. patent 4,457,012 (see below), 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 ambience generation to compensate for loss of ambience resulting from the noise reduction.