Sunfire Stereo Amplifier (325x2)

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Sunfire Stereo Amplifier (325x2)

Post by TNRabbit » Sun Oct 28, 2007 3:51 pm

Sunfire Stereo Amplifier (325x2):

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Link to article:

http://www.regonaudio.com/Sunfire.html

Text of the article:

The Sunfire Amplifier: All the Amplifier You Will Ever Need

This article is reprinted as a tribute to a superb audio design. The Sunfire and its companion piece the Lightstar (similar power supply, a different "voicing"), ushered in a new era in which amplifiers of moderate price competed with and in many respects outdid the high-priced "super-amps". But this article and the companion article on the Lightstar that appeared a few issues later are also reprinted as my specific tribute to Harry Pearson's editorial management. As the reader will see from the footnote exchanges in this article , not to mention the text itself, I was expressing views here quite contrary to HP's own in many respects, and also, in good part, views at odds with the view of most TAS writers of the time. A small-minded or mean-spirited editor would have either "killed" the piece or asked for a rewrite. But HP was tolerant of controversy and generous of spirit to his writers. He asked for high professionalism, but he never required adherence to anything resembling a party line. And he published the article as I submitted it. Moreover, when he expressed his disagreement in the footnotes, he allowed me what the politicians call equal time to answer back. Like Voltaire in his famous dictum, HP disagreed with what I said, but defended my right to say it, even in the pages of his own magazine. A writer cannot ask for more from an editor. This is just to say thanks , HP, for letting me say what I believed in this article, and always, whether you thought I was right or not. This grand tradition of freedom that HP started fortunately continues in TAS to this day and constitutes a treasured part of HP's legacy.

The essence of design is control. The objet trouve may have its attractions, but the greatest accomplishments of art, science, or craftsmanship are accessible only to those who control their medium completely. Raphael's School of Athens could not have arisen as street art. The Beethoven Ninth Symphony could not have been improvised by an inexperienced amateur. Amplifier "design by listening" is a charming phrase, seeming to combine the process and the goal. But the charm is meretricious if it amounts to some "audiophile designer" wandering around in an electronic parts house sticking resistors, capacitors, and tubes or transistors together, hoping for some magical sound. That won't work. "You have to know what you are doing" is the motto behind real accomplishment.

When it comes to amplifiers, few others know what they are doing as well as Robert Carver. Whatever one thinks of the Carver challenge, where Carver claimed to be able to duplicate the sound of any amplifier (within power limitations) by modifying the circuit of one of his own, the very fact that he could get dose proves a point: He can control the sound of his amplifiers to an extraordinary, perhaps a unique, extent.* (Personally, I believe that he can do what he claimed, at least so nearly that the differences are unimportant. But that is beside the point here.)

When you listen to a Carver (1) amplifier, you are listening to the sound Carver intended. I am not familiar in any detail with earlier Carver designs. But, to go straight to the point, the Sunfire is among the best of amplifiers. Never mind the reasonable price, nor the absurd question that has preoccupied some reviewers of whether Carver is a true High End designer-as if that were some mystic priesthood-nor the fact that the Sunfire is enormously powerful, which to some implies automatically, in a vast misunderstanding of how things work, a lack of refinement. The Sunfire stands in the top ranks, defying all such preconceptions.

In the realm of would-be ultimate amplifiers, there are the eccentric absurdities, the micro-watt single-ended triodes with their 8 ohm output impedances, that function as a combination of harmonic distortion generators and tone controls, much beloved of those discontented with the sounds actually recorded. Then there are serious attempts, both tube and solid-state, at accurate reproduction of the input signal. Many of these work very well indeed and come close to or even get to being good enough, given how bad speakers and source material are.

It is a curious, but not inexplicable, fact that these latter do not sound precisely alike. Much of the variation among them is attributable to what amounts to a choice of electronic parameters. As I shall discuss momentarily, a modicum of signal alteration is bound to occur, and choices arise from the type of signal alteration chosen. To my ears, the parameter choices of the Sunfire are highly consonant with music. In any case, such choices have relatively small musical impact. More to the point, the intrinsic behavior of the Sunfire, outside such more or less arbitrary and unimportant choices, is superior to virtually all others.

You can spend more money. Depending on your personal preferences and your speaker system, you might find an amplifier that sounded better to you. But you can't buy an amplifier that is demonstrably better, and you will have a hard time finding one that is as demonstrably good. (2) Moreover, to my ears, you will even have a hard time finding one that sounds better even in that evanescent realm of personal preferences based on parameter choices. The Sunfire certainly stands in my own personal top echelon. Given this situation and the price of the Sunfire, it seems fair to say that the Sunfire redefines the situation of audio amplification. As of now, we have a whole new ballgame.

With sonic excellence duly promised and description forthcoming momentarily, let me first explain a general technical point: Almost everyone who has given serious thought to the interaction of amplifiers and speakers has come to realize that speakers can make large and rapidly varying current demands under the dynamic conditions of actually playing music. These demands are much larger on occasion that one would expect from averaged impedance measurements under static (fixed-frequency sine wave) conditions. In effect, under dynamic conditions, speakers can act as if they had much lower impedance with much - nastier phase angles than a normal impedance plot would show. As a consequence, amplifiers have to be prepared for more extreme demands on their power supply than designers used to believe. This point is being explicitly addressed by a number of contemporary designers. (3) In the Sunfire, Carver addresses it with a vengeance. The Sunfire has enormous current capability. With nominal 8 ohm wattage of 300, the Sunfire is capable of bursts of 2,400 watts into a 1 ohm load. Without taking away in the least from the technical accomplishment of attaining such performance in a relatively small, lightweight amplifier, I want to emphasize the sonic consequences, rather than any details of how the power supply design works, obviously remarkable though it is.

The Sunfire will drive anything with ease. And the ease is apparent. Low-current amplifiers can get into trouble at surprisingly low levels, for the reasons already noted. Most tube amplifiers, for example, clip audibly when asked to produce the hard transients of the top notes of the piano in fortissimo at anything resembling close-up live levels and with usual speakers. A certain shatter of these notes is almost inevitable. The Sunfire never gets into such troubles. And this extra ease seems to me apparent even at such very low levels that almost any halfway sensible amplifier would be operating nominally within its technical limits. ("Halfway sensible" rules out the SE triodes, which are subliminally clipping and current limiting all the time, and, of course, which clip outright often, except with horn-loaded speakers or others of comparable sensitivity.)

This sense of ease at low levels might be psychological. The absolute certainty that nothing will go wrong when the music gets loud may just make one feel more relaxed. But, psychological or not, that sense is there. This kind of thing can work the other way. Some of the supposed excitement of low-power, low-current tube amps, like some of the excitement of vinyl, is no doubt generated by subconscious waiting for clipping or mistracking, a sort of "Willie Makit, Betty Dont" effect. But that kind of excitement is something it is good to live without.

The Sunfire is very, very quiet in listening terms. (It is also quiet and cool in operation-no damned fans, no transformer buzz.) Music emerges from an absolutely black background. Part of this is just literal. The Sunfire has a low noise floor. The general question of noise is one of the great unsolved problems of audio. This was obvious in the days of analogue vinyl. One learned to ignore the background, but it was definitely there. And, as anyone who knows anything about psychoacoustics knows already, this noise was masking details like mad. (The distinctive sound of vinyl records has a great deal to do with certain types of detail being masked and other types not.) Even levels of noise that are by themselves inaudible can mask audible sounds. The Wagner family refused to air-condition the Bayreuth Festspielhaus because the air conditioning could not be made truly silent. The musicians know.

In any case, the perceived silent background of the Sunfire adds to one's sonic insight into the music. The amplifier also presents a wealth of perceived details. The perceived resolution of a piece of audio equipment is a complex matter, though you would never guess how complex from reading those audio magazines that seem to believe that a single word always corresponds to a single, unified phenomenon. (Some even give numerical rating in categories, unbelievably.) But it is likely that the apparent resolution of the Sunfire is associated with the combination of its quiet background and its fast-acting and unflappable power supply. Whatever the reason, the Sunfire presents a highly detailed sound picture, without presenting an aggressive tonal balance in the least.

Indeed, in tonal terms, the Sunfire is the opposite of aggressive. And with this we come to one aspect, at least, of the parameter choices I mentioned earlier. Another semi-technical digression is needed here.

A perfect amplifier in the theoretical sense would be a pure voltage source. That is, it would generate a voltage at its output terminals that was a constant multiple of its input voltage, independently of what load was connected across the output terminals. This ideal is unrealizable for at least two reasons.

For one thing, a voltage cannot be maintained across a "dead short," and there is always a lower limit in practice to the load impedance an amplifier can handle. For the Sunfire, the lower limit is low indeed.

The second limitation, and the one to the point here as far as tonal balance goes, is that amplifiers must have an "output network" in order to be stable. Typically, their output impedance must include a small amount of inductance, rather than being literally zero. Without this, they would be unstable at ultra-high frequencies. Carver's observations suggested to him, if I understood him correctly,(4) that the interaction of the typical output network and a typical speaker load often resulted in a slight lift in lower treble frequency response, if the amplifier measured flat into the standard 8 ohm resistive test load. (This observation is for transistor amplifiers. The tube/transformer situation is different.) Thus Carver designed the Sunfire to have a slight, broad, but gently sloped depression in this region so that the result was more nearly flat into real-life loads. Of course, real-life loads are a variable thing. And Carver said that, if anything, he erred in the direction of less lower treble, on the reasonable ground that an excess of lower treble is far more annoying than a slight deficiency there.

The effect is noticeable, at least on familiar speakers. After my first listen on the Quad 63's, I commented to my wife, "I don't know if it is right, but it surely is pretty." She agreed. But, in fact, it may very well be right more often than not, and certainly no amplifier will always be exactly on the target of exactly flat into all loads.

I would emphasize that we are talking here of small and smooth response changes, not the large roller coaster rides of some tube amplifiers, especially single-ended triodes.(5) Carver is admirably straightforward about this. And, given how far speakers are from flat, I think it is quite silly to get in a lather about exactly which balance one wants out of a transistor amplifier, all of which are essentially flat compared with speakers, anyway. (These various small non-flatnesses do make for reviewing difficulties, since they tend to be heard as other sonic qualities.) In any case, Carver's choice with the Sunfire came out to be musically satisfactory with all the speakers I tried. And the tonal shift, compared with the brighter amplifiers, never sounded like a coloration in any sense. Indeed, switching back to a brighter amp was likely to sound far more like a coloration.(6) (Steeliness does not equal transparency, whatever else you may read.)

Another aspect of the Sunfire deserves special comment: the bass. The bass is extremely firm and extended, without being exaggerated. Again, one is tempted to think the current capability contributes. Another factor is the very low (1 Hz) -3 dB point, on the Normal input. There is also a Lab Direct input with no roll-off at all. In principle, this is superior, but the difference is subtle and one needs to be sure there is no DC offset in the preamp. This extension into the low lows, or all the way down, is well known to have definitely audible good effect on phase response much further up in the midbass, where phase is highly audible, as demonstrated in the famous KEP experiments years ago, among other places. In any case, the Sunfire's bass performance will extract the best from your speaker in that department.

What of the midrange and treble?---smooth, grain free, true to source, and neutral in the context indicated. It is hard to rave about a really good amplifier here because what it is doing is nothing, nothing to alter the character of the source. (For example, an amplifier with "liquid midrange" is a musical instrument, not a good amplifier, as HP has so often pointed out.) Outside the balance "voicing" already noted, the Sunfire is without character. After the initial adjustment to the exact tonal balance, necessary with any amplifier, the Sunfire simply ceased to exist as a perceived source of signal alteration. One listened to the source and the speakers (none free of coloration, that's for sure, unfortunately).

And what of soundstage? Here I want to take a hard line: The soundstage performance of an amplifier is not a separate thing, alone unto itself. It is compounded of resolution, tonal balance, low distortion, and so on. * The tonal balance choice of the Sunfire makes images slightly more distant and increases perceived depth, compared with most of the alternative choices, and less compared with others. So what? (7) Does the Sunfire "soundstage" well? Of course, because it is a terrific amplifier. Does it "soundstage" better or worse than other high-quality amplifiers? This is unknowable, but I would opt for the answer "better than most" because its quietness and detail presentation and other non-stereo virtues must make its true soundstage performance better too.

The Sunfire is one of the great triumphs of audio design and one of the greatest bargains in audio. The only real point of reproduced music is access for everyone. Prince Esterhazy could (and did) hire Haydn to organize an orchestra for him to listen to; so could the financial princes of today. That those of us who cannot and do not exploit the lives of others are nonetheless provided with music---that is the glory of the age of recordings. But the equipment has to be affordable. The Sunfire is a plausible purchase for a great many people, if one thinks of it as a permanent investment. It is built like a battleship and will be providing musical pleasure long after your new car has gone to the crusher. Meanwhile, you can get on with the difficult task of finding speakers and recordings worthy of it, and then listening to the music.
-REG

Postscript: The Sunfire has a unique feature I didn't mention earlier because I don't consider it to be serious. It has a second set of output terminals labeled Current Source, which is a euphemism for the insertion of a 1 ohm resistor in series. Biwiring with the tweeter attached to these will attenuate the tweeter output, which in many speakers will be all to the good, but in others not. Otherwise, the Current Source terminals will induce all the response irregularities of a 1 ohm output impedance tube amplifier, turning the elegantly neutral Sunfire into a coloration machine. (You can form your own opinion of reviewers who have preferred this degradation of performance without even a careful description of its cause.) Maybe Carver wanted people to hear for themselves how important it is for an amplifier to have low output impedance. (If so, the trick seems to have backfired a bit.) Little jokes are the privilege of genius: Beethoven liked them, Ives is full of them. Theirs, and Carver's, are all right with me. But a perceptive listener won't use the Current Source taps for long, unless, strictly by chance, the associated intrinsic inaccuracies compensate in part for those of your speakers.

*HP If he could, then why didn't those particular amps sound like the great ones?

§ But I am speaking of his personally-executed modifications, not what was marketed.-REG

1 Throughout, Carver means Carver the man, not Carver the corporation, fr.om which the man is now separated.

2. Many amplifiers work better than any speaker and alter the signal far less than the recording process alters sound. It has been a long time since the power amplifier was the weak link. But very few amplifiers work as well as the Sunfire.

3. See, for example, my review of the Chord 1200B, Issue 100.

4. Personal communication.

5. See my article "Why Amplifiers Don't Always Sound Right: Output Impedances and All That" in Issue 71.

6. It is interesting that several of the technically oriented journals failed to notice the shift in response, adjectives such as "ruler flat" (into the standard test load) being used. Makes one wonder... (One happy exception to the sleeping through: Andrew Marshall's Audio Ideas Guide.)

* HP thinks it more nearly a measure of time---i.e., phase-relationships.

§But no broadband solid-state amplifier has any substantial phase nonlinearities.-REG

7 Incidentally, the Carver Corporation's Lightstar amplifier embodies power supply principles similar to the Sunfire, but with, I gather, a different choice of balance. So something along the lines of a comparison is possible. But I have not had the opportunity to carry out this comparison. I am instead comparing the Sunfire to other, entirely different transistor amplifiers.


ROBERT E. GREENE'S ASSOCIATED EQUIPMENT

Front End(analogue):

Townshend Audio Mk III, Nakamichi TX-lOOO turntables; Graham 1.5st, Morch DP-6, SME III pickup arms; Audio Technica ATML-170, Stanton CS-100 cartridges

Electronics:

Plinius 12 preamplifier, Sunfire and Credo amplifiers

Speakers:

Quad ES L-63; Soundwave Pointsource 3.0, Spendor SP-1/2

Cables &: Interconnects:

Goertz flat interconnect & speaker;Promethean interconnect

Accessories:

Townshend Audio Seismic Sinks



Manufacturer :Sunfire Corporation
P.O. Box 1589
Snohomish, Washington 98290
Designer:Bob Carver
Source: Manufacturer loan
Price: $2,175
Warranty: 5 years parts and labor

SOURCE: REG on Audio, http://www.regonaudio.com
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Re: Sunfire Stereo Amplifier (325x2)

Post by OconeeOrange » Wed Nov 03, 2010 4:58 pm

Good reading.
The old Carvers are big, heavy and throw some heat.
Sunfire is light and cool.

Makes no sense to me.

Seems like a Sunfire would be better, but something about the old 600X2 keeps it at the top of my "want list".

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