My Sunfire reference amplifier (reviewed in issue number 60) is one of the most powerful solid state amplifiers available. But like all wattoholics my need for more power is insatiable. I always want and need more power. Sure, the Sunfire's 300 watts into eight ohms (per channel, continuous) and 600 watts into four ohms (per channel, continuous) is more power than most audiophiles have at their command. Some even say power figures of this magnitude are far in excess of what any sane audiophile requires for aural satisfaction. I respectfully disagree. There are many reasons why more power is the way to go, but the main reason (at least for this guy) is that more watts produce more realistic sound when music is played at or near concert hall level.

One needs lots of watts for realistic sound, more than most realize. Bear with me as I quote Julian Hirsch (again) from the September, 1992 issue of Stereo Review, an article titled, "Power-How much is enough?" To quote Julian: "¼let me assure you I have often listened to CD's of orchestral music whose average level did not exceed 5 watts but whose peaks approached 500 watts. And this was at volume levels that did not preclude conversation in the room."

I can hear it now. Julian Hirsch! What does he know? Everyone in the tweak world has taken their shots at Julian. And many of the shots have been vicious personal attacks on the man. But I dare anyone tell me that the man can't measure! Not even the tweak lunatic fringe deny his measuring talents. In fact, the one common criticism parroted by the tweak masses is that all he does is measure. If Julian measures almost 500 watts you can bet it is almost 500 watts. And if almost 500 watts doesn't preclude conversation in a room imagine the wattage necessary when conversation is precluded by a symphony orchestra playing fortissimo! The more watts the better¼.period. Enter the Sunfire Signature amplifier.

Surprisingly, the guy responsible for the impressively powerful Sunfire Signature amplifier seeing the light-of-day is not Bob Carver, but Sunfire's marketing and sales V.P., Randy Bingham. No, amigos, Randy didn't design the circuitry but he's the guy who pushed hard for an amplifier that is twice as powerful as the original Sunfire. Bob Carver will be the first to admit that he didn't see any need for anything more powerful than the Sunfire amplifier. And many would probably agree with the boss. But as one who has some sales/marketing experience I can tell you that the job of a sales/marketing manager is to express his feelings on what he thinks should be included in the product line and not to necessarily always agree with the boss. Hell man, if you want a sales/marketing type who always agrees with you just appoint yourself! Anyway, Bob Carver went with Randy's insistence for a more powerful amplifier. Us wattoholics will be ever grateful to Randy for an all powerful amplifier and, of course, Bob Carver, for the unique circuitry to accomplish the job!

The circuitry, given the name of tracking down converter, results in maximum power output with minimal heat. The minimal heat is a not-so-obvious plus that places the Signature into an "Energy Pollution Preventer" category; minimal heat not only means "energy efficient" but also cost efficient. The tracking down converter circuitry keeps the Signature cool without the need for expensive and heavy cooling fins. Anytime you see cooling fins on an amplifier keep the following in mind: Those machined or extruded aluminum heat fins painted with heat dissipating black paint are expensive to manufacture, add appreciable weight to the amplifier, and are an indication of inefficient circuitry. Stated simply, high heat dissipation means higher purchase cost and higher operating cost.

One could say that Sunfire Signature is the same as the Sunfire in all respects….almost. This sameness means that like the Sunfire, the Sunfire Signature is unique in having two different outputs, or sonic signatures, per channel. There's a low impedance, solid state output labeled voltage source, and a relatively high-impedance (1 ohm), tube-like output labeled current source. There are balanced and unbalanced inputs with the unbalanced inputs having two options; a lab direct input (DC to 80kHz response) and a normal input with a response of 1Hz (3dB point) to 80kHz.. Three fuses protect the voltage source output, current source output, and the AC line input. The Signature comes in at 50 lbs. and is packaged in an attractive brushed aluminum, black anodized case. A crystal base is included upon which the Signature may be placed to insure that air flow isn't restricted, particularly if it's placed on a carpet.

Two obvious exceptions that separate the Sunfire from the Sunfire Signature (from this point the older but smaller output sibling will be referred to as the Sunfire, and the more powerful Sunfire Signature as the Signature) are the front panel meter scale and an original Bob Carver signature, also on the front panel of each Signature amplifier. The meter on the Sunfire indicates 380 joules of energy available whereas the meter on the Signatures indicates 475 joules of available energy. The Signature amplifier has an original Bob Carver signature, emblazed in gold-type material, on the front panel, hence the name, Signature!. This original signature on each Signature (!) is also the idea of Randy Bingham; you'll either love or hate the idea; I think it's neat. No two amplifiers are exactly the same. In fact, I did a rigorous double-blind comparison between the two amplifiers in for review and I was able to distinguish the slight difference in signatures between the Signatures 100% of the time! And that's very difficult to do with both eyes closed (double- blind.... get it?)! A third but not so obvious difference is weight; the Signature weighs in at 50 lbs. compared to the Sunfire's 43 lbs.

The fourth difference between the Sunfire and the Signature is a signature (metaphorically speaking) of a Bob carver designed amplifier. Lots of clean, inexpensive watts. And the Signature amplifier gives one about as many clean and inexpensive watts as a wattoholic needs. Would you believe 600 watts continuous, per channel into 8 ohms? Into a 4 ohm load it's 1200 watts continuous, per channel. The Signature will also handle 2 ohm and 1 ohm loads with corresponding outputs of 2400 and 4000 watts (I.H.F. test signals). The doubling of the output capability of the Signature (compared to the Sunfire) is attributable to a larger power supply, including a larger transformer (a good part of the increased weight), the very heart and soul of a power supply. And for those who think it's important: Sunfire's transformers are hand-wound (!) at their satellite manufacturing facility in a nearby town!

At this point I am not able to do any direct measurements to confirm these figures. Confirming the above stated output wattages requires resistors of low ohmage capable of handling extremely large currents. A combination of low resistance and high current translates into a resistor(s) that must be able of dissipating mucho heat (high wattage) and such resistors cost mucho dollars. In fact, as this review is being written, I have placed an order and am waiting for a set of resistors capable of handling the enormous power this amplifier is capable of generating. If the resistors arrive in time I will include an addendum to this review that will provide more information on the published output specs of this amplifier. But I can't wait too long, for as the editor says: "I would rather have a review that is completed and submitted than a review that you intend to complete and submit!"

I might also mention that Peter Aczel (another measuring master) measured the output of the Sunfire amplifier (See issue No. 23 of The Audio Critic) and the measured specs easily exceeded the published specs. I would be willing to bet a lot of money that the Signature will meet or exceed the published specs.

My love for realistic sound levels and an amplifier capable of producing many watts could easily result in the untimely death of a speaker. Keeping this in mind I went with the Carver Platinum Amazing MK IV's as my speakers of choice for this review. The MK IV's are about as bulletproof as a speaker can be. In addition to being one of the best sounding speakers ever made (regardless of price), they're one of the few speakers capable of handling amplifier outputs that would melt and shatter other speakers. With the MK IV's the problem has always been one of running out of amplifier power!

I should mention that I had installed the passive biamp upgrade kit that allowed the MK IV's to be used with the crossover's high and low sections fully integrated or electrically separated. With one duly noted exception in this review I opted for the integrated crossover approach with the speaker being driven by the voltage source/transistor-type output.

I choose not to go with a subwoofer. The MK IV's-with four twelve inch woofers per side-are one of the few speakers that go low and loud enough for my aural satisfaction. More importantly, I wanted all the lower end to be amplified by the Signature amplifier. It's the low bass frequencies that will test the output mettle of an amplifier.

Using the voltage source/transistor type output to drive the MK IV's I went for broke. Choosing a CD to challenge the Signature (and the MK IV's!) was easy. The winner is Bainbridge recording BCD 6285/SONIC BOOMS 2. Tracks 33 through 37 are the sounds of the Space Shuttle Atlantis lifting off. The resulting Sound Pressure levels (SPL) begin to approach the actual bone shaking experience of being there. I said approach, not equal! To achieve 100 plus dB levels at relatively low frequencies and sustain these levels for extended periods of time requires an amplifier that has the output capability of an arc welder! The Signature provides Home Theater sound levels from a conventional two channel system! Not to belabor the point but smaller (power-wise) amplifiers just aren't going to be able to approach realistic SPL's with this recording. The Signature gives you loud with a vengeance. Speaking of loud.... An indirect indication of the Signature's increased output power-compared to the Sunfire-is the fact that the SPL levels measured several dB higher for a given setting of the preamp volume control. No, not proof positive, but an excellent indicator of increased output.

To hell with the loud and inaccurate sound of Home Theater say the two channel purists! What about the more purist and demanding requirements for the sound of music and song by real instruments and voices recorded in real world settings? Well, I for one refuse to join the broad brush condemnation of Home Theater sound. But...the Signature is a traditional two channel amplifier, so what about some good old fashion two channel listening and commenting on the sound.

Let's choose reference CD's that are readily available to everyone, keep the selection to no more than two CD's, and include the voice on at least one of the CD's. My CD's of choice are Delos 3137, Mount Saint Helens Symphony, Gerrard Scwartz conducting the Seattle Symphony, and Verdi's Requiem, Bainbridge recording BCD2103, Oberlin Musical Union and Orchestra, Daniel Moe conducting.

The Mount St. Helens Symphony encompasses the full range of a symphony orchestra, from pianissimo to fortissimo. This music represents the symphonic equivalent of the extremes of nature which translates into demanding extremes being placed upon the amplifier; from the sleepy quiet of a gentle breeze making its way across Spirit Lake at the foot of St. Helens to an instantaneous erupting force emanating from the very bowels of hell. The third and final movement (Volcano) goes from subdued, hymn-like to hell-like in a flash; this almost instantaneous transition from quiet to a lengthy stentorian level of sound requires-as the tweaks would say-an amplifier that is quick and capable of sustaining dB levels easily in excess of 100 without faltering. The Signature does both with ease.

The Verdi Requiem is demanding but in a different manner. The mixture of altos, sopranos, tenors, and basses (210 in all) combining with an eighty piece orchestra will cause you to quickly leave the room if everything isn't just right. Don't ask me why but from time immemorial the most difficult test for an amplifier is to reproduce a massed choir. In this case, a mass choir also! For some reason a massed choir will cause an amplifier to distort at levels which are loud but not seemingly excessive. I suspect that we are so attuned to the human voice (the primary means of communication since day one) that even the slightest onset of amplifier clipping is instantly recognizable as distortion. It seems that an orchestra has to be playing much more loudly for the onset of clipping to be recognizable. Anyway....this recording (which did produce audible clipping in an unnamed, $30,000 amplifier owned by my friend when I was living in Germany) of Verdi's Requiem is a thing of sonic beauty when played through the Signature.

Now for the pièce de résistance. When Randy Bingham chatted with me regarding the Signature he insisted that since I had done the MK IV biamp upgrade (having the option of electrically separating the low and high pass filters of the crossover network, including the installation of a second set of input connectors per speaker) I should at least give a listen to the MK IV's configured in a passive vertical biamping configuration. As you may or may not know passive vertical biamping requires that each speaker (left and right) be driven by its own dedicated amplifier. One channel of the amplifier drives the high frequency section and the other channel drives the low frequency section. Simple enough, huh? But keep in mind that in addition to the standard low impedance output (voltage source) for each channel the Signature also has a high impedance (current source), tube-like output for each channel. So....

Per Randy's request (and the fact that he had sent me a second Signature just for this purpose!) I finally succumbed to the Sunfire ads that plead for the transistor-type current source to be connected to the low frequency portion of the speaker (four twelve inch woofers) and the tube-like current source output connected to the high frequency ribbon. Voilà! Transistor-type output to the woofers for tight and loud bass. And tube-type output to the ribbon for warm midrange and sparkling highs. Okay, so I am having fun, but....having given it a try I can easily see how one could become hooked on this configuration. Dare I say the soundstage size seems to increase dramatically and instrument detail seems to jump out at you? You bet. So what are my thoughts on this hookup versus a conventional, transistor output to an integrated crossover?

The conventional voltage source/solid state hookup is likened to a photograph of an object. It's accurate, has minimum coloration, and leaves very little room for interpretation. The current source/tube type-hookup is likened to a painting of the same object. There all sorts of interpretations for the painting and beauty-or lack thereof-is in the eyes of the beholder. In the final analysis the sound you prefer will depend on many things, not the least of which is that indefinable something called personal preference. I prefer the photograph, but....if the photograph wasn't available I could easily live with the painting.

A measurement I was able to do involved checking the frequency response characteristics of the Signature. Using a test CD (PIERRE VERNY PV 784031) I measured the dB output (at the speaker terminals of the MK IV's with the crossover's high and low filters connected and using the voltage source/solid state output) at 18 frequency points, from 20 Hz to 20Khz. Just as with the Sunfire the resulting graph was essentially a straight line with a very slight dip (less than 1 dB) at the upper frequencies. I feel confident that had the points been plotted using the typical non-reactive resistors as a load the resulting graph would have been close to ruler flat. Obtaining a linear frequency response with a real world load (the crossover circuitry) indicates minimal coloration of the sound. Perhaps I should say the Signature is a straight wire with lots of gain!

The negatives are minimal. The output connectors are five way, plastic binding posts. I would prefer the gold plated variety, a la the Sunfire. The absence of a power switch drives me crazy but that's the way it is in today's audio world. The instruction manual is an eight page, minimalist product; it definitely should be better.

At $2, 995 the Signature isn't inexpensive. But if you break down the cost-per-watt price it is inexpensive! I did a quick check of cost-per-watt for several other amplifiers using the October, 1997 issue of AUDIO magazine (the annual equipment directory) as my reference for obtaining output specs for cost comparison purposes. I am not going to go into on the various comparisons but I will state the following: The Signature gives you the most watts for the least cost of any standard, off-the-shelf, consumer type audio amplifier. If I am wrong I will acknowledge any rationally stated exception to the above statement. Please keep in mind that cost-per-watt is calculated by dividing the cost by the sum of the output wattage for a given impedance. To wit: The cost-per-watt of the Signature for the 4 ohm output is $2,995 divided by 2400 (the sum of the 4 ohm channel outputs), or $1.25 per watt.

If accurate sound, realistic sound levels, and pricing sanity are your things then the Signature has few, if any, peers. I listened to the Signature reproduce sounds ranging from Schubert's Trout Quintet to the Space Shuttle lifting off. The Signature reproduced all of the nuances of Schubert's subdued, delicate masterpiece and all the pants flapping awesomeness created by the sound of man's venture into space. Not many amplifiers can reproduce such a wide gamut of sounds so accurately and effortlessly, and those that do cost far in excess of the Signature's $2,995 selling price. If you are about to spend $2,995 or more on an amplifier please do yourself and your pocketbook a favor and don't, at least not until you've given the Signature a listen. Highly recommended in the $2,994 to $50,001 price range.