I live in an apt so cannot make any changes to existing circuits.

I read that a 15A circuit should suffice for 770/990 combo, provided that 770 runs on its dedicated 15A.

BUT, like I said, I live in an apt and the best case is if I run an extension from the kitchen - where the sole 20A circuit outlet resides - into the living room. The cord will be about 20 ft long.

Even then, the 770/990 will have to be on the same circuit.

This leads to my question - would this setup even work?

1) Running a 20-ft extension from a 20A outlet.
2) Running all HT equipment (990/770/plasma) from it, aside from subwoofer.

Much thanks.

I would just run the 770/990 from your 15 amp circuit. I am going to assume that since you live in an apartment, you can not play your system at levels anywhere close to the power output levels you could get from your 770. If you have a problem with the circuit breaker tripping, then see the next paragraph.

There is no reason too that you can not use your 20 amp circuit in the kitchen as well. Just use an extension cord that has 12 gauge conductors. The only issue you might have though is if you are using your system and you use the microwave or some other high current appliance that is on the same kitchen circuit.

oddly enough, the apt is wired such that all kitchen appliances draw from the 15A circuit that's in the living room. So I don't really have much of a choice but to run from the dedicated 20A in the kitchen.

So, just to make sure...
1) #12 cord is good enough? No need for #10?
2) What constitutes "anywhere close to the power output levels"?

Does that mean if I have 5 monoblocks each eating up 1500W, but b/c I won't play at such loud vols, I can actually run them all on a 15A circuit? (I state this b/c I actually do have monos but have to downgrade since I thought my apt won't be able to handle the load).

Much thanks.

The max power output of an amp (especially in the realm of multichannel home theater setups) is somewhat theoretical - driving all seven channels (or even one or two channels) to a level near that rated max is very difficult. Those 5 monoblocks (or five channels of the 770) could output 1000W (and probably consume 1500W from the wall), but short of some sort of speaker torturing, ear drum shattering, earquake simulating test tone you would not actually reach those power demands. You could simply use the 15A circuit in the living room for the entire system and never have a problem - I actually ran my system at my old house on a 15A circuit shared by kitchen, living room, and bathroom (with a Model 750 amp, Parasound two channel amp bridged to mono, subwoofer, 27" TV, and source components). Plus I would personally prefer not to have a heavy cord like that running exposed that far in my home - just feels a little iffy to me.

gonk,

I think you may have misread... FYI, this is the spec of ONE of my 6 (I had said 5... I miscounted) monos that I thought I might need to replace due to insufficient power handling of my apt.

Output Power..........................300W (8W), 600W (4W)
Class-A Power........................100W (8W)
Frequency Response..............5Hz - 40kHz (+/- 1dB)
Input Sensitivity......................1 V
THD..........................................≤ 0.01%
S/N Ratio.................................97 dB
Input Impedance.....................47kΩ
Dimension (WHD)...................17" x 7" x 21"
Weight....................................80 lbs

Each of the 6 has a 1500W torroidal transformer. So, essentially, I think I have the equivalent of ~6 770s...

Now, I don't think I can run them on a single 15A circuit. Can I (if so, then I guess I won't need to buy the 770)...

Based on your initial post, I thought you were using a 770, hence my response. We should probably take a moment to look at what speakers are being used - if they are particularly low efficiency speakers (which would be the most likely explanation for the monoblocks you have currently), then you'll need a good bit of power available to drive them, but if they are more reasonable efficiency then the easier load and the volume limits of apartment living might alleviate much of the trouble.

FRONT:
Description: 3-way, 3-units
Frequency Response: 28Hz—40kHz (±3dB)
Dispersion: Horizontal off-axis 30°, –3dB
Sensitivity: 89dB/W/M
Impedance: 4ohm
Power Requirement: 50—250W recommended
Tweeter: G2 aluminum ribbon shielded design
Midrange: AC-130MKII 5.25" long linear excursion
Woofer: AC-250MKII 10" long linear excursion
Crossover Frequency: 180 Hz and 3500Hz, 3rd order
Connections: Gold-plated bi-wire binding posts
Dimensions (HxWxD): 42" × 11.5" × 13"
Net Weight: 90 lbs/each

REAR & SURROUNDS:
Description: 2-way, 2-units
Frequency Response: 42Hz—40kHz
Dispersion: Horizontal off-axis 30°,–3dB.
Sensitivity: 88dB/W/M
Impedance: 8ohm
Power Handling: 100W.
Tweeter: G2 aluminum ribbon tweeter shielded design.
Mid-woofer: AC-130MKII 5.25", Φ25mm copper-coated aluminum voice coil with flat wire, 5mm maximum excursion.
Crossover Frequency: 3000Hz, 3rd order.
Crossover Components: Mundorf-Supreme capacitors (M-cap), 5N copper inductors, and metal oxide film resistors.
Connections: 5-way gold-plated mega binding posts.
Dimensions: 14" × 9.5" × 11" (HxWxD)
Net Weight: 25 lb/each

CENTER:
Description: 2-way, 3-units
Frequency Response: 45Hz—40kHz
Dispersion: Horizontal off-axis 30°, –3dB
Sensitivity: 90dB/W/M
Impedance: 4ohm
Power Rating: 150W
Tweeter: G2 aluminum ribbon shielded design
Mid-woofer: AC-130MKII 5.25" shielded design
Crossover Frequency: 3200Hz, 2nd order
Connections: Gold-plated binding posts
Dimensions (HxWxD): 7.5" × 24" × 11"
Net Weight: 40 lbs/each

The reason why I have the monoblocks is b/c of a super deal with the above speakers.

Also, would the 770 be sufficient for these speakers?

You could be driving each of your speakers with just 10 watts, and have your room filled with sound in low 90dB area. Can you play much louder than that in your apartment? I too thought you already had the 770.

When you say class A power (100 watts), what is that? Does that amp work in a purely class A mode below 100 watts? If that is the case then its idle current draw would be very high?

I really think you can run all your mono blocks on the same circuit as long as you are not running all of them at high power levels i.e. 100 watts to all channels at the same time.

The only other issue I could see is if the mono blocks are triggered on at the same time. If they do not have a soft-start circuit in the power supply, the surge of current pulled from the outlet to charge caps can trip circuit breakers. One or two amps might not be a problem, but six at the same time might be.

Yes, purely class A below 100W. I know the idle current draw would be very high but not sure how high.

If anything, http://sound.westhost.com/class-a.htm says that I won't be able to reliably run 6 amps on a circuit at all, given that a 8W class-A amp draws 17~48W @ idle. So even if I don't run all of them at high power levels, I'll still have an issue due to the highly inefficient design of the class-As.

I'm contemplating the 770 to replace my monoblocks (I know... quite a sad downgrade ). But maybe the 7125 would suffice?

What is the brand of amp and speakers?