Carver Research Lightstar Reference power amplifier

When it comes to amplifiers, ya gotcher tubes, yer solid-states, and yer hybrids. Although amplifier manufacturers would have you believe otherwise, the majority of designs within each category are variations on a few fairly-well-known themes. Everyone agrees that the power supply is extremely important. Most designers try to obtain the amplifier's desired frequency response and distortion characteristics with a minimum of negative feedback. It's also agreed—at least among designers of solid-state amps—that the ability to drive a variety of speakers, including those that present a low-impedance and/or reactive load, is an important priority.

In the spirit of high-fidelity, the amplifier's output should bear a close resemblance to the input signal ("straight wire with gain"), and to whatever extent the output is different from the input, the difference should be in a musically pleasing direction. Once priorities are set—and decisions have been made about such practical matters as cost, weight, size, heat dissipation, power consumption, etc.—designing an amplifier is often little more than applying tried-and-true principles and techniques. With careful attention paid to such factors as parts selection, circuit layout, and vibration control, such amplifiers can sound quite good; but to the audiophile who wants something different, they're a bit, well, boring. As Miss Peggy Lee put it, "Is That All There Is?"

I first found out about the Carver Research Lightstar Reference amplifier while reading Peter W. Mitchell's 1994 WCES Report in April 1994. Judging by Peter's description, the Lightstar was not your standard could-have-been-designed-by-a-computer amplifier: "A remarkably clever, innovative, and cost-effective design that promises to deliver huge power levels to any load," quoth Mr. M. At Stereophile's Hi-Fi '94 High-End Show in Miami last April, I had a chance to listen to a system featuring the Lightstar, and I, too, came away impressed with its potential. I was keen to check out how it would perform in my own system.

Description & design
To those familiar with the built-to-a-price offerings from the Carver Corporation, examining the Lightstar will be a surprise. It's heavy, and very well-finished—almost to a Krell/Mark Levinson standard. The 3/8"-thick black-anodized aluminum chassis, which also functions as a heatsink, has a "wraparound" design, with no visible screws or bolts on the top or sides. The Lightstar's front panel is dominated by two illuminated power meters; at night, it looks as if you're being stared at by some sort of robot or monster with bright slits for eyes (footnote 1). Whether you consider this the pinnacle of high-tech or simply gimmicky will be a matter of individual taste, but it certainly looks striking. Personally, I would have liked to have been able to turn off the power meters—or at least the lights—while listening late at night.

The Lightstar is described as dual-mono. To this end, it has two power cords and two power switches in the back. In normal use, these switches are left in the On position, and the amplifier is controlled by a single front-panel touchplate switch, which toggles from Standby to Active. The top of the amplifier chassis was somewhat warm even with the amp in the Standby mode, and became much warmer when playing music, but never to the point that I couldn't touch it comfortably.

There are balanced and single-ended inputs, two sets of high-quality binding posts for bi-wire capability, and switch-selectable high-gain operation for use with a passive preamplifier or for direct connection to a CD player. I used the standard-gain mode. The Lightstar is protected in three ways: a thermal switch activates a mute circuit if the heatsink temperature gets too high; similarly, short-circuiting the output engages a mute circuit until the condition is remedied; and finally, if the rated current is exceeded for more than 10 seconds, the power switches on the rear panel, which are actually resettable magnetic circuit breakers, turn the amplifier off. For once, I did nothing to engage any of these protective devices!

So, what's so special about the Lightstar's design? Carver's literature on the Lightstar states that the design team had two basic goals: first, to restructure the signal path for a more neutral amplification of the audio signal; and second, to develop a high-current power supply capable of driving virtually any loudspeaker. They also wanted the amplifier to be impervious to AC-line noise, spikes, and line-voltage variations, and for signal amplification to be unaffected by reactive loads. I'll leave the technical description of how they actually did it to Peter W. Mitchell (see Peter's sidebar, taken from his 1994 WCES Show report); interested readers can write to Carver Research for the Lightstar's white paper. Carver's Jim Croft told me that the development of the Lightstar was very much system-oriented—selecting what worked best in a particular context. For example, they found that there was an optimal power-supply capacitance value—higher or lower values didn't sound as good.

Initial impressions of the Lightstar, using the PS UltraLink II processor and the CAT SL-1 Signature preamplifier, were quite positive; but before I could do any serious listening, I had to complete a variety of other tasks, including some surround-sound–processor reviews for the Stereophile Guide to Home Theater, and the Follow-Up of the latest version of the Dunlavy SC-IV loudspeaker.

Then I got a call from Carver, who told me that they had discovered a potential problem with the Lightstar that surfaced if the line voltage was too high. Apparently, one of the design briefs was to allow the amp to work with lower-than-normal line voltages, but they didn't look at the effects of voltages that are higher than normal. It was subsequently discovered that this can cause some subtle high-frequency distortion.

The line voltage where I live tends to be on the high side—I've measured as high as 129V—so this could have presented a problem. Not to worry—they had a mod (footnote 2) that would fix things, so I shipped the review sample back to Carver. By the time I got the modified, ready-to-cope-with-any-voltage unit back, I had changed my digital front-end to a Sonic Frontiers SFD-2, and was using a Sonic Frontiers SFL-2 line stage with a balanced connection between the SFD-2 and the SFL-2.

Footnote 1: One of the power-meter needles was poorly aligned with the zero mark when in the resting position, and did not match the other meter when playing music or with a test signal. I assume this to be a sample problem. (The review sample of the Lightstar was from the first, limited-production run.)

Footnote 2: This mod has been incorporated into current Lightstar production.

Carver Corporation
Company no longer in existence (2018)

Bogolu Haranath's picture

"Blinded by the light" :-) ..............

georgehifi's picture

They've gota be the ugliest square waves I've ever seen from a solid state amp. With 1st overshoot ring on the trailing edge!!! What's that all about????

Cheers George

Anton's picture

I would be an avid reader of a column that “reviewed” vintage gear compared to current equipment. Yes, I know it would be tough making sure the gear was up to snuff based on age, but reading a comparison between a Sony CDP 101 and the current Rega would be fascinating.

Sign me up as a reader of the Anachrophile column!

Allen Fant's picture

Beautiful looking amp. While I never had an opportunity to demo a Bob Carver amp per se, I did have a wonderful audition, with his 1st Sunfire amp in 1996.