Sunfire Signature 600x2 Amplifier Review-Martin Appel

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Sunfire Signature 600x2 Amplifier Review-Martin Appel

Post by TNRabbit » Wed Jul 16, 2008 7:18 am



Over the past four years I've had the pleasure of reviewing several of Bob Carver's Sunfire products, the True Subwoofer Mk II and the Theater Grand II, a tuner/preamp/processor. Both products were favorably reviewed, appreciated and spent quite awhile in my system. Both products have since been superceded by later versions. I've recently upgraded to the latest version of the subwoofer, the Sunfire True Subwoofer EQ. I also can report that he is now up to the Theater Grand IV version of the processor. These products were trendsetters, both in technical innovation and in value for the dollar, which seems to be a constant with Bob Carver designed products: innovation, creativity and value. None of these qualities would mean a hill of beans if there weren't a concomitant level of high performance that went along with his designs.

Carver, a designer of legendary stature and one of the pioneers in this industry, has always had unique approaches to audio design, starting way back in the 70's with his 400 watt mini-cube amplifier and his sonic holography [oh, the memories - Ed] circuits for his preamplifiers, to name a few. He has a specific sound in mind and designs his products to achieve those goals. If you read his White Paper describing his design philosophy, he talks about, among other things, about how he voices his amplifiers. I'll paraphrase here by saying that if the female voice sounds correct spatially and timbrally, followed by a male baritone voice, then he's nailed the design. Once these listening parameters are established, the sound of a symphony orchestra, will be correct as well, both in terms of its resolution of textures and timbres along with the representation of its soundstage. One might say whose voices or which orchestra, in what venue does Carver have in mind when he makes his final voicing decisions. Whether or not his idea of sound reproduction coincides with yours makes the subject so interesting and challenging and prone to never ending debate. Read his White paper in its entirety for both his technical and philosophical approach to design. It is both illuminating and thought provoking.

In all these years, I had never had a Carver designed amplifier in my system and thought it was time to see what all the fuss was about. I called up Randy Bingham at Sunfire (Bingham has since moved on) and requested Carver's latest effort in amplification for review. A very cordial fellow, he immediately recommended that I try the Sunfire Signature 600~two, Carver's statement stereo amplifier, and would ship it to me immediately. I awaited its arrival with anticipation.


The Architectural model of the amplifier is 17 inches wide rather than the standard model width of 19 inches. The performance of both models are said to be identical. They both come in a black, brushed finish with a substantial aluminum face plate containing a rather large 'retro' style meter calibrated in joules (up to 500 joules). In typical use, this meter hardly moves at all. You can adjust the brightness level of the meter, via a switch on the underside of the amp, from a warm subtle tube-like glow to a brightly lit lamp. You choose. And, of course, you get the Bob Carver signature, which he does sign himself, on the faceplate. Included in the box, with the amplifier, is a matching glass shelf with raised rubber feet for the unit to sit on for ventilation purposes.

The rear panel offers various inputs, single ended (RCA) as well as balanced (XLR) connection options and a detachable power cord. There is a small, three-position toggle switch which allows the user to keep the amp continuously on, off, or in a signal sensing third position that turns the amp on or off, automatically, when an audio signal is detected. The left and right speaker output terminals offer two distinct sets of connection options: one set of speaker terminals labeled 'Current' and one set labeled 'Voltage', for each channel. According to the clearly written instruction manual, 'The Voltage source output has a source impedance of approximately zero ohms and the current source has a source impedance of approximately one ohm.' The Current source connection is said to correspond to the output of classic tube amplifiers. An interesting option to explore.

There are recommendations to use the Current source outputs to connect to if one has, electrostatic, panel or ribbon speakers and Voltage source for cone based systems and subwoofers. As Carver points out, and any interested party would surely do, is to experiment and let your ears make the decision.

Bi-wiring is easy. With the amp having two sets of outputs per channel, one can, for example, use the Current outputs for the upper frequencies and the Voltage outputs for the lower ones. Again, let your ears decide. The Sunfire also comes with a detachable power cord for after market experimentation.

If 600 watts per channel into 8 ohms, is not enough for you, one can also use two of these powerhouses in monoblock configuration. 1200 watts per channel, 8 ohms. Or maybe you want a hydro-electric power station, too! What I'm trying to relay to you is how utterly flexible and powerful this amplifier is. Oh, there is also a 12 Volt DC trigger input included as well.


Since one has a choice, Voltage or Current, for connecting the amp to your system, as I've described above, I'll report to you on both. Burn in was achieved after about a hundred hours and my comments pertain to both modes of operation. Later in the review I'll explore some of the differences, between the two.

First let me state right from the beginning that this amplifier is extraordinary in producing an absolutely grain free, detailed presentation with music emerging clearly out of a black velvet background. As detailed and quiet as my reference, the Innersound ESL 300MK II, is, the Sunfire may exceed it, with a matter of ease that at first, takes you by surprise. It doesn't shout detail at you it just flows out naturally. Images seem to have more substance and body; palpability, if you will. This amplifier presents the music with a sense of naturalness without hard edges. This does not mean that transient attack or transparency suffer at all. Quite the contrary, it is extremely transparent and let's you see into the music. Sound staging is another forte of this amp (Voltage taps). The stage is wide and deep, reflecting the source. It will not create a false sense of depth if the source doesn't have it.

I decided to test Carver's hypothesis by starting with female vocalists. I listened to Patricia Barber, Jacinthe, Diana Krall and Eva Cassidy to name a few. In all cases, the voices were portrayed with a smooth naturalness, body and bloom reminding me of high quality tube amplifiers. Every delicate nuance of voice shading and texture was deliciously revealed by the Sunfire amplifier with image focus that was dead on.

Male vocalists were also handled with equal aplomb. From breath intakes to inner voice textures and chestiness that said this was a human being making this sound forming a complete vocal picture. Frank Sinatra, on his Only The Lonely CD, sounded so there and three dimensional. On One For My Baby, one could imagine the smoke filled bar with the piano playing in the rear left and the bartender listening to the soulful Frank singing his lament. This amp delivered the scene vividly, smoke and all.

One observation I found in comparing it to my Innersound ESL 300 MK II, was that voices thru the Innersound seemed, ever so slightly, more forward with a smidgen more inner detail. The Sunfire's, by comparison, was slightly recessed, but perhaps smoother. Telarc's Ray Brown, Some Of My Best Friends Are…The Piano Players, has some of the best recorded acoustic bass there is and the Sunfire portays it with weight, slam and drive. The only nit to pick is that compared to the Innersound's rendition, the bass' timbre was a tad drier, but had ever so slightly more body. An interesting difference to ponder. Which one is correct depends on your preference. Needless to say we are talking about two excellent amplifiers.

Two of my reference recordings for classical music are RCA's LSC CD Stokowski Rhapsodies and Telarc's superb 50kHz transfer to DSD's hybrid SACD of Mussorgsky's Pictures at an Exhibition with Maazel and The Cleveland Orchestra. These stunning recordings were reproduced with full orchestral weight and impact while providing the illusion of a three dimensional spatial experience. A wealth of inner detail and articulation was in full evidence providing that touch of elegant nuance that flute or oboe solos have, or a triangle strike from the rear floating over the orchestra, with accompanying breath intakes, musicians' movements, chairs creaking and sheet music being turned.

I also spent significant time listening in the Current mode; I preferred the Voltage taps. It seemed that in the Current mode, the midrange was even more tube-like and glorious, imitating single ended tubes. The problem was, to these ears, the reduction in extension when it came to the frequency extremes as compared to the Voltage taps. It seemed to glorify the midrange to the detriment of the overall balance. Some might prefer this, but I preferred listening, in the final analysis, to the Voltage taps. Additionally, in Current mode, the soundstage depth seemed artificially deep, a little over the top for my taste. Many tube lovers will be amazed at how tube-like the sonic presentation is and recommend to anyone considering this amp to listen long and well to both modes. Having this kind of choice in a solid state amplifier is extremely unusual. It's like giving your system a choice of two flavors.

In either mode, it is apparent that Carver has taken his love of the sonics of tubes and merged them with the power, extension, control and dependability of solid state and produced one superb amplifier with the attributes of both. The Innersound has been my reference and it's earned a well deserved Audiophilia Star Component Award. On the other hand, the Sunfire has seduced me. I think I'll be fickle and give up one star for another. As I sit here and finish this review, the phone rings and it's Gary Leeds, from Innersound, wanting to know if I'd like to review his newly designed i 330 amplifier. Stay tuned.

Manufacturer's Comment

Thanks for the great review. The fact check is all correct. Your sensitivity to what Bob Carver is trying to do with the Sunfire amp is greatly appreciated and admired. You have described the sound very accurately. Your comparison with the Innersound gave both brands credit.

I did not see a list of ancillary equipment. It would be interesting to know what pre-amp you were using. Sunfire does make a matching pre-amp known as the Classic Vacuum Tube Control Center. This glorious piece retails for $2995. Would you like to match that up with the Sunfire Signature 600~two power amp for a system review or shoot-out some time? Just let me know.

Jeremy Fry
Director of Marketing, Sunfire Corp

Sunfire Signature 600~two Stereo Power Amplifier

S1920 Bickford Avenue Snohomish, WA 98290
Phone: 425-335-4748 Fax: 425-335-4746
Price: US$3,995.00
Source of review sample: Manufacturer Loan
Copyright © 2004 AUDIOPHILIA

From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.

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