Product Review - Sunfire Signature Power Amplifier - May, 1998

Stacey L. Spears


Two Channel Power Amplifier: 600 watts rms/channel into 8 0hms, 20 Hz to 20kHz

Mfr. FR: 1 Hz to 80 kHz

THD: 0.5% at full output

Input Impedance: 470 kOhms

XLR and RCA inputs

Size: 6 1/2"H x 19"W x 15 3/4"D

Weight: 50 Pounds

MSRP: $2,995


Sunfire Corporation., P.O. Box 1589, Snohomish, Washington 98291; Phone 425-335-4748; Fax 425-335-4746; E-Mail [email protected]; Web

"More power," are the famous words of comedian Tim Allen. It seems that Bob Carver has followed this philosophy by taking the Sunfire power amplifier and upgrading it. You can read the review of the original Sunfire by JEJ @ Here. That amplifier came out 3 years ago. For a short time, Bob will be literally pouring his heart and soul into the Signature version. He hand-signs each one on the front (we've seen him do it) and checks each one to ensure that it meets his standards.

From the cosmetics, you would not know that the Sunfire Signature Amplifier is different from the Sunfire Amplifier, except for the authentic John Hancock of one Bob Carver. It has the candlelight yellow readout on the front that displays how much power (Joules) is stored for the tracking downconverter. The meter reads a little higher on the Sunfire Signature than on the Sunfire, for obvious reasons.

The rear panel has numerous connectors. First are the inputs which include Lab Direct, Normal (both unbalanced RCA), and Balanced. The Lab Direct DC couples the input, and assumes that your preamplifier does not have any DC offset. Normal and Balanced have protection against DC offset. There are two sets of outputs, Current Source and Voltage Source. The Current Source outputs have higher output impedance (1 Ohm) in order to produce a sound that is more like a tube power amplifier, while the Voltage Source outputs are conventional low impedance outputs (0.01 Ohm) like most solid state amplifiers.

Even just plugging the amp in, it is very obvious that this is a bigger beast. The power supply stores more energy, as the Joule Meter needle on the front is nearly pegged. On the original Sunfire the needle is at about ¾. Just as with the first model, I wish there were a power switch. Not putting power on/off switches on hi-fi components is vogue these days. It forces the user to leave the power on, which is better for the component, both in sound quality (no warmup period) and longevity of the parts (power surges at turn-on shorten their lives). You can just leave it plugged in, and this way the amp will always be warmed up and in its optimum state. Alternatively, you can plug it in everytime you want to use it, or you can plug it into a power strip that has an on/off switch. I usually left it plugged in on the weekends and un-plugged it during the week while I was at work. I'm more comfortable with this approach, warmup period or not. I recommend getting your AC wall circuit upgraded so that you have the amp plugged into at least 20 amps of supply. This amplifier will use all the juice you can give it, especially if you are using it to drive low impedance speakers.

At the heart of the Sunfire is the magical tracking downconverter. Although downconverters themselves are not new, this particular design is unique (patented) to the Sunfire products. Without going into much detail, the tracking downconverter stays 6 volts above the music signal at all times, so it is very efficient, and the amplifier stays very cool even at high volume (the output transistors only have to dissipate 6 volts x the current, which, even if it were 10 amperes, would only be 60 watts). If you want to know more about this technology, you can read it by clicking here. Because the amplifier is so efficient with its use of the power supply, the output doubles from 600 watts per channel at 8 Ohms to 1,200 watts per channel when driving 4 Ohm loads, and 2,400 watts per channel into 2 Ohm loads. This will be dependent on the availability of sufficient current from your AC wall outlet.

The inside of the chassis is packed with the power supply . . . an excellent sign. An enormous toroidal transformer occupies most of the space, along with two large power supply capacitors. The output stages are on two PC boards, one on each side of the chassis. Notice the absence of heat sinks. This is due to the very efficient handling of power.

The Sunfire allows for several different methods of hook-up. The normal operation is to use the voltage source output, which is the standard amplifier output. The current source output is recommended for electrostatic speakers. You can also use a combination of the two by wiring your low frequency drivers with the voltage source, and midrange and treble drivers with the current source. I tried both of these configurations and will elaborate more on them in a moment. There is also the parallel mono option where you use a Y-connector with one preamplifier output plugged into one leg of the Y-connector. The other two legs of the Y are connected to the two amplifier inputs. One channel output goes to the woofer, and the other channel feeds the midrange/tweeter. Of course, you need two Signature amplifiers for this. There is no bridging option.

During my listening sessions, I configured the Signature in two different ways. The first was with the Sunfire Classic Vacuum Tube Preamplifier being driven by the Meridian 508-24 CD player, and the Signature driving a pair of speakers for two channel stereo. The second method was in a home theater setup using the Signature amp to drive my front left and right speakers. I used the Sunfire Cinema Grand to power the other channels, with a Pioneer CLD-97 LD player and Sony S-7000 DVD player as sources. For speakers, I utilized Monitor Audio and Mirage OM-6s. All cabling in both situations was with Nordost Flatline.

Reviewing an amplifier is not always an easy thing. Listening for what makes one amplifier sound better or just different than another is a long subjective process. I spent several nights enjoying the spacious sound of the Signature amp.

Lorenna Mckennets Mummers Dance has the Celtic feeling that truly comes to life. Other CDs that I used for the listening tests included Rebecca Pigeon and Holly Cole. "So and So" from Holly Cole’s "Don’t Smoke in Bed" is on of my favorites. Her voice flows with such smoothness. The bass is right behind her, and the performance, while not totally in my living room, comes close to being there. I even threw in a little country, not something I normally listen to, but Shania Twain's "Your Still the One" is such a beautiful song. From Classic to Country or from Jazz to Rap, everything sounds good when being driven by the Sunfire Signature.

Bob Carver has always done some cool things with his products, and the current and voltage outputs are an example. I liked the way the amp sounded when using the current source output for the midrange and tweeters and using the voltage source for the woofers. The top end sounded a bit more open, very spacious if you will. It was easier on the ears. This configuration is an option, not a requirement, but I am from the school that says listen to what you like.

I mentioned earlier that I also put the Signature into my home theater setup. To have three Signatures on hand would have been a rush, but I was still able to get excited with just one. The latest film from Wesley Snipes, "One Night Stand" on DVD has a beautiful musical score to accompany the film. There were several scenes when I was sure that I had real musicians playing in my living room. The DTS version of Disney’s "Hunchback of Notre Dame" is a good demo of DTS and a musical where the sound is as superb as the video quality. One last film I watched and listened to, that really blew me away, was "GI Jane". Riddly Scott’s soundtrack was mixed very well and can only truly be appreciated on a high quality audio system, and the Sunfire Signature fits into this category nicely. Of course, "bringing M-16 bullets to life" may not be the socially acceptable way of using the dynamics of a 600 watt per channel amplifier.

At $2,995 the Sunfire Signature is a bargain. Most amplifiers that are capable of this much power usually cost at least 3 times the price. The Signature is only available for a limited time, so I recommend searching out your local Sunfire dealer and listening to one of these before it's too late.

Stacey L. Spears

© Copyright 1998 Secrets of Home Theater & High Fidelity
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