Sunfire Standard or Signature Edition

The Tell-tale sign... model 300 operates at about 390 joules, 600 signature about 470 joules.

Also, back of Sunfire Signature 600
https://www.ukaudiomart.com/details/649279940-sunfire-signature-600-ii-one-of-the-most-powerful-ampl...

https://forum.audiogon.com/discussions/sunfire-signature-what-is-this

Thanks LowRider57. Good information. I saw the second post you referenced before I started this thread, and I was still confused. Both of my amps have the 19" chassis, and both have the captive power cords. I noticed that in the Series II manual, both the Standard and Signature show IEC connections, and I couldn't find a manual prior to Series II. So I guess I don't have a manual for my amps. Oh well, I bought them right and will likely bridge them and used them both for my B&W 802D's or Martin Logan Odysseys. Those speakers like a lot of power and it sounds like the current source might help them breathe. Then I'm going to sell either my McIntosh MC452, or my Mark Levinson 332 after George Meyer unbricks it. 

Yeah, that’s the same manual that I used. Bridging and bi-amping them is the way to go. I used one amp rated at 300wpc, 600w into my 4 ohm speakers... sounded terrific in my 12’ x 16’ room. Non-fatiguing, wide and deep 3D soundstaging, and a powerful low-end.

A little known fact; these first generation Sunfire’s are not fully-balanced. XLR input is shorted to single-ended. Will you be using balanced cables? This will prevent any ground-loops and provide a lower noise-floor.

Here are specs for these amps...
Sunfire 300 Power Amplifier - Class AB:
- 300 watts/ch into 8 Ohms, 600 watts/ch into 4 Ohms
- frequency response 1 Hz - 80 kHz, balanced and unbalanced inputs
- input impedance 42 kOhm
- Input sensitivity of 1.64V for rated power (300W)
- output impedance 0.01 Ohm (voltage source),
1 Ohm (current source)
- Output voltage (@ 8W) is 48.9V
- Damping factor 150

2nd generation 300-2 is fully-balanced....
- Input sensitivity for rated output:
Unbalanced: 1.64 Vrms,
Balanced: 0.82 Vrms
- XLR Input impedance:
10 kΩ, each leg balanced to ground Female XLR
Pin 1 is ground Pin 2 is positive (hot) Pin 3 is negative (cold)

Notice the difference in input sensitivities.

Hi, probably should start another thread but since Lowrider57 has some very good knowledge of Sunfire Amps will ask here: The 400 fives - how do I tell the newer, maybe signature 2 models? Can I tell by which side the speaker posts are on the back? I see some are grouped on the left and some on the right. Thanks.

I owned a Sunfire Cinema Grand Signature 405 X 5 amp for a while and it was signed on the front.  I don't know if that is the case with all the Sunfire amps.