Wow! I'd like to find a way to replace my 7700 with a 7900. Maybe the Outlaws will cut me a special break since one of the channels in my 7700 failed (fuse looks okay) and I'm going to have to send it back anyway.

A few questions for any knowledgeable person:
(1) How does the 7900 select between the unbalanced and balanced inputs? The 7700 has a small switch for each channel to select which input is connected to the amp. But it looks like the 7900 has no switches. Does it automatically select the connected input based on signal present? Or based on cable/shield ground present? If it is an auto-selector, I guess the only downside is for anyone who is connecting two sources, one balanced and one unbalanced, and using the switches to select between them.

(2) How well will a 7900 work with both plugs on a single 20A circuit? What is the real maximum power input possible combined between the two inputs? If I plug both inputs into a single 20A circuit that could provide 2400W.

The 7900 has 7 * 300W = 2100W of power output capability but the input is somewhat higher due to inefficiency. The 7700 output 7 * 200W = 1400W with a spec max input of 1800W giving an efficiency of 78%. This same efficiency applied to the 7900 would yield a max power input of 2692W.

So it seems like the 7900 power input could exceed a single 20A circuit under absolute max loading, but not by much. It needs about 22.4A peak, if my math is right.

I'll probably use 5 of the 7 channels at this point so I think that would need 16A or 1923W, fitting well within a 20A circuit. Anyone think I'll ever exceed a 20A circuit or experience any sound degradation in this configuration?

Comments and math corrections appreciated!

Thanks!
-Dan

p.s. - the height dimensions is messed up on the webpage. Does it intend to say 9.5" high? This sucker is so huge I better make sure I have enough space!