Most of the better multichannel amplifiers on the market today are five channel and are limited to 100 or 200 watts per channel. This limitation is due, in part, to both physical size and the ability to get rid of heat effectively without introducing noisy fans. Larger power amps, 200-400 watts or more, are often relegated to mono amps, which means you have the impractical task of installing up to five separate amp chassis in your studio.
Product PointsApplications: Studio multichannel monitoring, high-end home theater
Key Features: 800 W per channel; balanced and unbalanced inputs; voltage-source or current-source outputs
Contact: Sunfire Laboratories at 425-335-4748; www.sunfire.com.
I recently discovered a multichannel amplifier that not only offers high power and current for professional multichannel applications, but also runs cool: the Sunfire Laboratories Cinema Grand Signature Edition.
The Cinema Grand Signature, priced at $3,750, was created by renowned amp designer Bob Carver, who now heads Sunfire Laboratories. His amp’s unique power supply and output circuitry allows the amp to crank out more than 400 watts per channel into 8 ohms, more than 800 watts into 4 ohms and 1,600 plus watts into 2 ohms! All this power is housed in a box that measures only 19 inches by 6.5 inches by 16.75 inches and weighs 42 pounds. No fans and no bulky heat sinks.
At the heart of this new amplifier, which Carver said is his best design yet, is a patented “tracking downconverter,” which acts almost as a second power amplifier. Here is how it works: a massive main power supply feeds the tracking downconverter. The tracking converter’s output is fully regulated and tracks the audio, receiving its input signal from the same source that drives the main amplifier.
The tracking downconverter uses 18 MOSFETs to produce the necessary output voltage that essentially becomes the rail voltage for the output devices. This voltage is synchronized with and modulated by the audio, hovering just six volts higher than the audio signal. Consequently, according to Carver, there is always adequate (6 volt) but not excessive headroom. Having more headroom than necessary simply wastes power which, in turn, ends up as heat.
The Sunfire amplifier has no heat sinks, the output devices are mounted on the vented bottom of the chassis. The Sunfire comes with a piece of smoked glass to place under the amp to ensure ventilation in installations where the amplifier would sit on carpeting.
Eight bipolar output transistors per channel, rated at 20 amps each, can deliver as much current as needed to almost any speaker load, including difficult low-impedance loads. The tracking downconverter supplies the right amount of voltage to the output devices – driving the speaker with as much total power as required. Sunfire Laboratories rates the maximum output current at 120 amperes peak to peak per channel.
For connection, the Sunfire features one balanced XLR and two unbalanced RCA inputs for each channel; the balanced inputs are, however, pin-3 hot, unlike the majority of the rest of the world (my only complaint).
Carver also offers a unique output feature on the Cinema Grand Signature: the three, front channel outputs give you a choice of “voltage-source” or “current-source”operation. Two sets of five-way binding posts per channel allow for connection to either or both outputs. The voltage-source output is said to have a typical solid state, almost zero output impedance, with the acclaimed, tight bass sonic signature. The current source output has a higher-output impedance (about 1 ohm) that is said to make the sound more like a vacuum tube amplifier.
Other amp features include a three-position, miniature toggle switch on the back of the amplifier that selects “On,” “Off” or “Auto,” the latter turning the amp on when it receives a signal from the left, front or center inputs. A dimly-lit meter indicates the energy reserve of the tracking downconverter power supply; it is calibrated in joules. The meter is not really necessary, but it looks cool and should remind you that this amplifier has plenty of stored energy ready to go.
During the amp’s break-in phase, I ran audio through the five channels over several hours; it became just slightly warm to the touch – proving Sunfire’s claim that the Cinema Grand Signature is indeed a cool-running amp.
I used the Sunfire Labs Cinema Grand Signature amplifier in my studio extensively for multi-channel SACD playback of material that I had recently recorded. The Cinema Grand drove five SLS S8R ribbon monitors.
In all my years of listening to scores of amplifiers, the multichannel Sunfire held its own with some of the better two-channel high-end amps I have auditioned. The current-source output is just as Bob Carver says, it is … “tube-like.” The midrange is smooth and natural, not a bit hard or harsh, while the top is open and airy with a very natural wide and deep soundstage. The current-source bottom end is not as tight as the voltage-source output, but to me the midrange and treble sounds more natural. This may not be the case with every kind of speaker.
With dynamic speakers, Carver recommends biwiring speakers with the voltage-source driving the woofer while the current-source drives the tweeter. I tried the voltage/current source biwire with the SLSs, but I liked the sound from the current-source-only outputs better.
On a per channel or per watt basis, the Sunfire Cinema Grand Signature amplifier is a good value for studio professionals. The fact that the amplifier can deliver all that power with so little heat is just icing on the cake.