Sunfire Signature... what is this?

If it says Signature on the back and has his signature on the front face as you say then it is surely a Sig 600. He did not make a Sig 300 etc....

If the binding posts have the red and black plastic covers, then it is a first generation. If the solid steel posts with an IEC, then the second version.

The 600 is very powerful and you should notice this immediately in your system.

I wasn't sure how much difference I would hear, going from one Sunfire at 800w/ch to another at 1200w/ch (4-ohm speakers).

The lack of difference was what made me start wondering.

All the manuals I can find on-line show 15-amp AC input fuse for both the 300 and 600 watt Sunfire 2-ch amps. Since this is a '99 model, maybe the 1st generation was different. And maybe I should send it to Rita's, for a tune-up.

Yes you are 100 percent right. Send it in and it will come back better then new. I could not believe the improvement. Also get an iec and use a better power cord.

Yours is the Sig 600 and I understand now that you already had lots of power before the 600.

The word "Signature" on the serial number sticker and the 480 Joule meter reading indicate pretty conclusively that you have the real 600 watt version. Also, it is likely your serial number is preceded by the designation "SS." This is yet another reliable indicator.
Carver has been profligate in post sale autographing. He'll sign pretty much anything he designed, so his signature on the front has come to mean very little.
Telling the difference between 400W and 600W is pretty close to impossible, all else being equal. This is only about a 1.5db difference, after all.
All of Carver's Sunfire "Load Invariant" designs use fundamentally the same circuit, with more or fewer output devices. They all sound practically identical, which is to say they all sound terrific.

Looking at some rear panel photos that are available on the web, and at manuals that are available at the Sunfire website for what appear to be comparable later models, it appears that the 5A fuses (changed to 6A in later models) protect just the "current source" outputs, not the "voltage source" outputs.

My guess is that the 600W rating only applies to the voltage source outputs, and the CONTINUOUS output power capability of the current source outputs is far less (with the difference between the two outputs in terms of short-term (dynamic) power capability being much smaller). I suspect that the current source outputs are created by just putting the voltage source outputs through low value resistors having high power handling capability. The fuses are probably provided just to protect the resistors, with the voltage outputs being protected by circuitry.

So the 5A fuse rating, corresponding to 200W into 8 ohms, is probably understandable. The 10A main fuse does seem somewhat incongruous with the 600W/channel rating, as the 1200W AC input it would support (120V x 10A) would require that the amp be 100% efficient to output 2 x 600W continuously, which of course is not possible. Perhaps it's a design oversight, or perhaps the 600W continuous rating is a bit optimistic.

Regards,
-- Al