Product Review -
Sunfire Cinema Grand Amplifier - July, 1996
By John E. Johnson, Jr.
Sunfire Cinema Grand; Five-channel power amplifier; 200 watts/ch rms into 8 Ohms; THD < 0.5%; Frequency response 20 Hz - 20 kHz + or - 0.1 dB; Rail 43 Volts rms; Input impedance 24 kOhm - unbalanced, 15 kOhm - balanced; Output impedance 0.01 Ohm Voltage source, 1 Ohm Current source; Size 6.5"H x 19"W x 15 3/4"D; Weight 45 pounds; Black anodized brushed aluminum finish; $2,375; Sunfire Corporation, 5210 Bickford Avenue, Snohomish, Washington 98290; Phone 206-335-4748; Fax 206-335-4746.
The Cinema Grand is Bob Carver's second product to be introduced from his new Sunfire Corporation. It is a 5 channel power amplifier designed for home theater use. If you set them side-by-side, it would be difficult to tell this amp apart from the original Sunfire 300 w/ch, 2 channel power amplifier that was introduced in late 1994 [click here to see review]. In fact, they use the same power supply with the Tracking Downconverter [click here for detailed description written by the man himself]. In most amplifiers, the output transistors always "see" the maximum voltage from the power supply rail. When a musical signal is applied, the speakers "see" a percentage of this voltage, depending on the strength (loudness) of the music. The difference between the voltage rail and the voltage at the speaker terminals has to be dissipated by the transistors as heat. With the tracking downconverter, the power supply follows the signal such that it stays just 6 Volts above the musical signal voltage required. In this way, the output transistors are never asked to dissipate more than 6 V x the current flow (voltage x current = watts), in heat. As a result, the Cinema Grand runs cold, even at full output, and no heat sinks are required. The power supply for the original Sunfire and the Cinema Grand is essentially the same: 12 International Rectifier HEXFETs. This is a massive power supply, and such capacity to deliver the goods upon demand is the heart of any good amplifier. The output devices are the same bipolar devices as are found in the original Sunfire, except that instead of 12 per channel, there are 4. The first question arises at this point: if there are 12 per channel in the original Sunfire, rated at 300 w/ch into 8 Ohms, and the Cinema Grand uses 4 per channel, rated at 200 w/ch into 8 Ohms, what is traded off? The answer is that the original Sunfire will deliver 2400 w/ch into 1 Ohm (such as certain electrostatic speakers), and the Cinema Grand is not rated for 1 Ohm loads at all. However, it will handle 4 Ohm speakers with no strain.
We tested the Cinema Grand using a Parasound P/SP 1000 Processor and Krix speakers, wired with Nordost Flatline. Laserdiscs included "Jurassic Park", "Sudden Death", "Sabrina", "Wild Bill", and others. The amp has two different sets of outputs for the front left/right channels. One set is a voltage source output, with an output impedance of about 0.01 Ohm. The other output is the current source, with an output impedance of about 1 Ohm. The theory is that the voltage source outputs will sound like a conventional transistor amp, while the current source outputs will sound more like tubes. In practice, these two different outputs do have slightly audible differences, with the voltage source sounding a little tighter. This is the one we preferred (voltage source), since, for one thing, all the other channel outputs were voltage source only. All the channels have balanced as well as unbalanced inputs. A few processors may have balanced outputs to connect with these. Our processor does not, but the balanced inputs can also be used with regular stereo preamps that have balanced outputs. There are two sets of unbalanced inputs (RCA jacks) for each channel, and by using a short jumper, one can connect the same input signal to two channels for bi-amping. A more complicated way of doing this would be to use a line level crossover in between the preamp and Cinema Grand, with the low frequency output used to drive one amp channel and the mid- and high frequency output to drive another channel. Otherwise, some of the power would end up being dissipated by the crossover components in the speaker enclosure.
The on/off switch is a very small toggle on the upper rear of the chassis. It has three positions: off, on, and standby. In standby mode, the amp waits for an electrical signal from the processor/preamp and then turns on. We found that just turning on the preamp and laserdisc player did not trigger the amp, and even when the first few silent seconds of the laserdisc were playing (the copyright warning is shown on the TV monitor, but there is no sound), the amp still did not come on. But, as soon as the movie began (logo fanfare for example), the amp came to life. The front panel has a meter calibrated in Joules, which represents the amount of energy available for delivery by the power supply. It reads about 380 Joules when the amp is on, and is illuminated in a soft orange color, much like a tube filament emits (Bob designed it this way). If the amp is overdriven, the reading on the meter will drop.
The sound from the Cinema Grand is delightful. Movie sound tracks are notoriously harsh, but they did not come out that way with this amp. Even when played loud, and I mean LOUD, the sound was never edgy, never biting. We turned the sound up as loud as we could stand it, and even plugged our ears and turned it up louder, but the Joule meter never budged (Bob . . . are you sure the meter is not just a picture of a needle pointing to 380 Joules?) Granted, the Cinema Grand is more expensive than most five channel amps, but the bottom line is . . . does the amp deliver? We will tell you as soon as we retrieve the roof of our lab from orbit. I understand it is due to re-enter earth atmosphere in June, 2003.
The nature of slew rate and amplifier sound is a controversial subject. This number represents the speed, in volts per microsecond, at which the amplifier output voltage climbs in response to the input signal [click here for a generic slew rate diagram]. A typical transistor amp has a higher slew rate (e.g., 100 v/usec) than a tube amp (e.g., 12 v/usec), and I feel this contributes to the softer characteristics of the tube sound. The Cinema Grand has a slew rate of about 14 v/usec, and I imagine this is one reason the movie sound tracks are not so irritating. The edginess is gone. However, for whatever reason this amp sounds the way it does, the fact is that it sounds terrific. I love it!
Conclusion: Another score right between the goal posts for Sunfire. Whether you are headed for Dolby Digital (AC-3), DTS, or plan on staying with Pro Logic, this fabulous power amplifier is recommended as a buy.
John E. Johnson, Jr.
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