Price Paid:  $2000.00 from AUDIO KING

Summary:
The Sunfire Stereo amp is in use with: Sony TAE-9000es pre-amp. Martin-logan reQuest fronts. Sony TAN-220 rear channel amp. Difinitive Technologies BP2X surround speakers Sony CDP-XA20es CD player. Acoustic Research ARS300 Sunfire powered subwoofer. Results: Using "small hall" or "live room" on the Sony pre-amp, the Sunfire could play transients to lifelike levels. Any of Brian Setzer Orchestra albums became startling with realistic attack and decay. The word phrase "dynamic range" now can be uttered. Forget SACD, get all of the sound out of the regular cd''s. This is the BEST front end amp in the world, period

Strengths:
More power and dynamics than most will ever need.

Weaknesses:
No power switch.

Similar Products Used:
Soundcraftsmen 5002, class H

Price Paid:  $1000.00 from ebay

Summary:
I must say that this amp is a pretty unconventional one when compared to its competition-- higher-end Parasounds, Brystons, used Krell, higher-end Rotels, etc.

Although the cabinet is only somewhat smaller than most amps of this power rating (300wpc@8ohms, 600@4, 1200@2!), its weight is the shocker-- only 42lbs! There are no massive heatsinks, and not even any cooling vents on the top of its black, brushed aluminum case. There are cooling vents to the sides and bottom, however.

When running for at least shorter periods of time, this amp runs amazingly cool (cooler than some preamps!), no matter what volume level is being played. The meter in front also doesn't vary much at all, and I presume it measures the power reserves in the tracking downconverter in joules. It certainly doesn't track the audio signal whatsoever. Based on all this I can see how many higher-end audiophiles would be very skeptical of this highly unconventional design.

Input and output options are quite varied, and should satisfy just about any setup. inputs include two sets of unbalanced phonos (lab-direct, and normal), and a set of balanced XLRs. Output is made via two sets of five-way gold plated binding posts. One set is for the voltage output (standard), one for the current output (for use with electrostatics, or for imparting a 'tube' like sound to your upper section mids/tweets in a biwire configuration).

On to the sound: Although I a still trying to sort this out, my findings do confirm that output via the current source does tame high frequency harshness tremendously. My amplification/speaker chain consists of an Adcom GFP-750 preamp running balanced to the Sunfire, which is biwired to a pair of NHT 2.9s. Voltage source for the woofers, current source to the mid/tweeter section.

Bass, while strong before, is possibly even more stupendous now. This amp can drive these speakers to very high sound levels without apparent strain. This, and the NHTs are known for being very power-hungry but with potent bass capability.

Part of this newfound bass, however, may be emerging at least partially because the high frequency output has been attenuated somewhat using the current output mode. The NHTs could sound somewhat tipped up, and even edgy and bright on certain source material. Now the tonal balance is much more to the laid-back side, and the sound is overall somewhat darker. Detail does not seem to be lost too much, but is certainly less prominent.

I could easily see how other users who have speakers that already err towards the laid-back side (Vandersteens, etc.) would think that the sound of this amp would be almost muffled. After all, it tamed the NHTs!

But then again, my old THX ultra amp was almost certainly on the bright side in terms of presentation.

Bass control of this amp, while not noticeably tighter or better than my previous amp, is certainly acceptable, and may indeed be better at higher volume levels. It has been said earlier that this does not seem like a 300w amp, and I have to agree with some reservations. It does not seem like it at lower volume levels, but I can fully believe it at high volume levels. It never loses control of the woofers, even at room-shaking levels. It's very disconcerting to hear and feel this power coming out of my speakers and feeling no heat whatsoever coming out of the amp's cabinet.

Overall: bass is juicy, plump, with possibly a slight bit of overhang but very good control at higher volume levels;
highs: presentation is relaxed, softened, and is best used in current output mode if the user's speakers are already on the bright side. An additionally heavily damped room could push this condition over the edge into unacceptability.

I got mine used on ebay for $1000, which I think is a fine value for a product of this quality. But at the SRP of $2500? Then I have to think again, because for that money you can get Parasound's HCA-2500A, Bryston's highly regarded 4b-ST, and a number of very high quality amps from other manufacturers. The competition is very tough at this price point, and a user should pre-audition all equipment in their home and think very hard about which amp would serve them and their system the best.

Strengths:
as everyone is saying: smooth presentation, not overly huge or heavy but with ample power reserves and good soundstaging. It's also an attractive piece of equipment with a better than usual array of input and output options, including balanced XLRs, and two sets of phono inputs, plus two sets of five-way binding posts for outputs.

Weaknesses:
if choosing the current output, highs may be perceived as slightly overly tamed

Similar Products Used:
Kenwood KM-Z1 THX Ultra amp, various

Summary:
I had to respond to some of the erroneous statements in some of the reviews here. None of the Sunfire amps are Class D switching amplifiers. The Amplifier circuit is a rather conventional Class AB type; the are no switching devices in the audio amplifier channels. What makes these amps unique is their power supplies. The Power Supply IS a switching type supply but it is unique in that it tracks along with the music signal. The supply is essentially a regulated power supply but instead of using an immovable static voltage reference(almost impossible to achieve), it uses the music signal itself. The advantage to this is that the output transistors of the amplifier do not have to dissipate the heat produced by having fixed power supply rails that are significantly greater than the average signal level. At idle the output transistors see only about 8.5 volts across them. As the music signal increases, the supply rails continuously track the signal. At full power the supply rails approach 120 volts.As a result, the Sunfire amps have no heat dissipation devices and yet still run cool.Another advantage to thse amps is that they cope extremely well with low impedance loads. The Sunfire amp will double its wattage into 4 ohms, double it again into 2 ohms, and if your circuit breaker can stand it double it again into one ohm.
What I like about this amp is that Bob Carver took a lot of time to voice this amp according to his musical tastes. It has the least fatigueing treble of any amp I've heard since the Aragon2002. Ironically, it is also quite detailed without becoming edgy. The Bass isn't as huge as a Krell but its very nice. The amp gets the midrange very right and after all, that's where most of the music lives.
This amp can be tweaked if you know what you are doing. Some benefits can be made by improving the parts quality; Do not try and alter the circuits themselves- it took a very bright man 5 years to perfect them. Do not apply ferrite beads to the power supply grounds- you want a low impedance ground at RF frequencies. Try litz or some other finely stranded ground wire. Try lowZ electrolytic caps with .01 uf polypropylene bypasses. Try replacing the 150pf, the 470pf and the two 750pf ceramic capacitors on each channel near the input jacks with polystyrene or polypropylene types. Note this will change the apparent soundstage from midhall to close to front row.

Strengths:
Smooth Treble, natural harmonic balance, spacious sounding

Weaknesses:
background hum is sometimes audible

Similar Products Used:
Adcom GFA555, Audire, Dyna400,etc

Summary:
A nicely made piece of kit.

Lots of power - even if not really sounding like all of 300W

This amp will never sound harsh - but it does smooth things over a little (although nowhere near as much as the Pass Aleph 3).

The Jadis stomps it in all respects (so it should at £10,000 / $15,000 !), the Krell (at a similar price) is less generous to fierce recordings but more detailed and accurate.

A reasonable value - especially if the rest of your system is a little on the forward side.

(The Signature version is supposed to address most of the concerns that I have listed.)

Strengths:
Power, smoothness, reasonable detail

Weaknesses:
A bit too smooth, I'm a detail fan - and the Sunfire didn't really make the grade.

Similar Products Used:
Jadis JA80, Krell KAV250p, Pass Aleph 3 (yuk!), EAR 509/2

Summary:
I wanted an amp with some authority to run my Martin-Logans (Aerius i bi-wires), but did not want an amp that impeded their lovely clarity and transperency. I came across Sunfire on the Web, as there are no local dealers in my area (ironic as I am in Sunfire's own backyard in Washington state). After considereable research, I tracked down a used example in my area and hooked it up to the ML's to give it a try. WOW! Right off that bat (it was already well broken in) the combination just sung beautifully. The combination was truly wonderful. I currently use only the voltage outputs (bi-wired with double runs of Kimber 8TC) as I have a tube preamp (Sunfire as well - also quite good)that tempers any tendancy to high frequency harshness the electrostatics might have (particularly with digital sourses). Using the current outputs for the panels is unnecessary in this system.
Clarity, tranperency, and control are the main characteristics of this amp. It lets the music com through with minimal influence. Quite simply I love it. It is an especially good value if you pick up a good used unit (can fint them at $1,000 if you look around).

Strengths:
Transparent, effortless power. Tweakable to work well in different systems

Weaknesses:
Could use better quality speaker terminals (the ones it has are completely serviceable though)

Similar Products Used:
Krell & Bryston