“People who are familiar with Carver’s design work over the years will realize that Bob doesn’t try just to make the same products as everyone else, only adding marginal improvements. Rather, he is an original thinker who reconsiders the philosophical underpinnings of every type of component he produces.”
Robert E. Greene, The Absolute Sound Magazine
Bob worked hard to become a physicist.
To pay the bills during college, he repaired television sets.
Most TV sets had tubes in them at that time; he learned their capabilities and limitations through practical experience…when he wasn’t studying for his physics degree.
This on-the-job introduction to electronics began his lifelong romance with vacuum tubes. Dare we say, "He warmed to them" ?
In 1969, while pursuing his Masters Degree, he built a 700-watt amplifier prototype housed in a coffee can. Phase Linear corporation, founded by Bob and Steve Johnston, was created to build and marketing this product. With 350 watts per channel it soon became the standard amplifier used in recording studios, sound
reinforcement companies, professional musicians and audiophiles.
It was followed by the Phase Linear 400 with 200 watts per channel, 4000 Series Auto-correlation Pre-Amplifier and Andromeda loudspeakers. For a detailed history, visit http://www.phaselinearhistory.stereomanuals.com/
In 1979, Bob sold his interest in Phase Linear and founded Carver. Fifteen years of innovative products followed including Magnetic Field Amplifiers, FM tuners and receivers with Asymmetrical Charge-Coupled Detection, and preamplifiers and receivers employing his Sonic Holography processing. Many are still regarded as sought-after classics as a quick search on E-Bay will reveal.
Bob doubled-down on loudspeaker design with The Amazing Loudspeakers, a ribbon and multiple cone transducer design that ultimately led (after countless iterations) to the Amazing Line Source decades later.
Bob never lost his fascination for tubes during his Carver years. He worked one into the output stage of his SD/A-390t CD P (still highly sought after) and created the first iteration of his money-is-no-object Silver Seven tube power amplifier, an advanced version of which we offer today.
The "auto-correlator" is a multi-band, single-ended dynamic noise filter with 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 Amp
"Magnetic field coil power amplifier" — audio amplifiers of the vacuum-tube era used transformers to convert the high-voltage, low-current output of the output tubes to a low-voltage, high-current output suitable for loudspeakers. 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 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).
In the real world, a sound produces a two sound arrivals, one for our left ear and one for our right. Stereo speakers produce FOUR sound arrivals. Each ear gets a delayed second arrival that muddies the sound stage. Through special processing circuitry, Sonic Holography cancel the second arrival, restoring clarity and realism.
Asymmetrical Charge-Coupled Detector
The "asymmetrical charge-coupled detector" is not the FM detector circuit of tuners, but rather 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. The result was a dramatically cleaner signal on weak or interference-prone FM stations. 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.
In 1994, Bob moved on to create Sunfire™ Corporation. In Bob’s words, “When I first started Sunfire, I realized the dealers were shifting gears, in terms of what they sold. Surround sound and Dolby® had taken off. Sunfire was one of the first U.S.-based companies to come out with a surround-sound processor with Dolby.”
At Sunfire, Bob expanded into high-back-EMF subwoofers and ribbon cinema loudspeakers, while still producing impressive power amplifiers, A/V receivers and processors (yes, there were tubes in many of the output stages!).
Sunfire is alive and well today, although Bob sold it to Core Brands, LLC., a subsidiary of Nortek™, Inc. in 2011. Bob Carver Corporation uses a highly-capable SubRosa Sunfire subwoofer as part of our Amazing Line Source speaker system. Why re-invent the wheel?
Pages from the 2004 Sunfire Brochure
That brings us to the present. Bob’s laboratory is just as jammed with gear as ever, although it’s now grown considerably into multiple labs and listening rooms. Several product line additions are coming soon. Sign up for our very-occasional newsletter and we’ll keep you appraised of developments.