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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 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, Sunfire in 1994 and now Bob Carver LLC in 2011.
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 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 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.
8,005,230 System for Digitally Controlling a Multi-Channel Audio Amplifier
U.S. Patent 3,727,148 Amplifier with Protective Energy Limiter Circuit Components
U.S. Patent 3,989,897 Method and Apparatus for Reducing Noise Content in Audio Signals (auto-correlator noise reduction)
U.S. Patent 4,218,585 Dimensional Sound Producing Apparatus and Method, (sonic holography)
U.S. Patent 4,218,660 Audio Amplifier and Method of Operating Same, (magnetic field coil power amplifier)
U.S. Patent 4,309,570 Dimensional Sound Recording and Apparatus and Method for Producing the Same
U.S. Patent 4,415,768 Tuning Apparatus and Method
U.S. Patent 4,4,450,95 Audio Amplifier
U.S. Patent 4,457,012 FM Stereo Apparatus and Method, (asymmetrical charge coupled stereo detector)
U.S. Patent 4,484,150 High Efficiency, Light Weight Audio Amplifier and Power Supply
U.S. Patent 4,586,002 Audio Amplifying Apparatus and Method
U.S. Patent 4,808,946 Lightweight, High Power Audio Amplifier and Power Supply
U.S. Patent 4,815,141 Apparatus and Methods for Removing Unwanted Components from a Communications Signal
U.S. Patent 5,748,753 High Power Audio Subwooferv
U.S. Patent 5,937,074 High Back EMF, High Pressure Subwoofer
U.S. Patent 6,166,605 Integrated Audio Amplifier
From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.
Sunfire TG-IV/400~7 Amp
Carver SD/A-360 CDP
Active bi-amp: Ashly XR-1001 & 2 Rane PEQ-15s
Main: HotRodded AL-IIIs
Sub: Klipsch RT-12d
Center: Sunfire CRS-3c
Surround: Sunfire CRS-3 (x 2)
OconeeOrange wrote:"Gary likes to play it 'loud' as do I. His system begs you turn it up until you die"
RIP WIlliam B. Dibble, 1948-2012. I'll miss you my friend.