Maybe in your locality.

In all the houses I've seen in Oregon the lighting is done on 14 gauge with a 15A breaker and outlets are wired with 12 gauge and protected with 20A breakers. Some spec houses might be wired as described (to meet minimum codes) but the custom homes I've seen are not wired that way.

In any case, the outlets are almost always of the 15 amp variety.


Charlie

OK Yoda. ;-)

AFAIK 'continuous' in the FTC use of the term means essentially forever, so the 'storage' capacity is a moot point.


Charlie

Charlie I live in NH where the Outlaws are from and the majority of the homes are wired 15 amp 14 gage. You also stated CUSTOM homes I believe thet would be the exception. We only use 12/2 20a for kitchens with a gfi breaker. Which would mean to target the masses you are stuck to 15a max at the outlet.

I doubt the common practice in their home state was a huge influence, and I also doubt a 90 pound, 7x200 watt home theater amp is really targeted to 'the masses' in any meaningful sense of the phrase.

I've never spent much time in the NE, but in the NW everything except old houses, trailer houses and a few lower end tract houses will have 12gx20a on the outlets. I've seen 14gx15a, but I've never done it or known anyone who would admit to it.

Not that it's bad or wrong - It's just not done much, at least not that I've been around. I suppose if a builder was REALLY tight it would be something, but copper is really cheap.

In any case, the 770 is almost certainly equipped with a 15a plug, so it shouldn't be designed to draw more than that for an extended period. Perhaps it's fused at 15a or maybe UL let it pass due to oversight or the reality (realistic duly cycle) of its' intended use.

I'm really most curious what it's musical power levels, short and longer term, are.

Have a good one,


Charlie

Hey guys... I'm an electrical engineer and have designed audio power amps so hopefully I can shed some light on the AC power rating versus the power output.

First of all, the most a standard 120 volt household product should be rated to draw is 1800 watts (which is the most you can safely get from a standard 15 amp household circuit). So that likely explains the 1800 watt rating on the back panel (and in the specs).

As for 300w x 7 continuous output, that would indeed require an even greater amount of power from the AC line. Most class AB audio amps are only about 60% - 70% efficient. So if we assume 70%, you have (300x7)/0.7 or a whopping 3000 watts of AC power draw!

This would require the amp to have at least two 1500 VA transformers which is unlikely. It would also cause a lot of AC line "sag" even on a 20 amp 12 guage circuit. Even if you somehow manage to provide 120 volts AC at 25 amps to the line cord, I doubt this amp will product 300 watts x 7 from all channels at once.

Running 200w x 7 out, you would still need about 2000 watts of AC but this is a more realistic number. The amp just might meet that spec (at least on the 3 channels that have a transformer to themselves) if they used 1000va min. transformers. The other 4 channels might have a harder time sharing one transformer.

In reality, however, even cranking your favorite bring-down-the-house DVD, the AVERAGE power consumed by the amp is unlikely to exceed 1000 watts even when pushing it to clipping. There will be plenty of power supply reserves to go around. This is how $299 100w x 5 receivers manage to sound as good as they do. On the test bench, with 5 channels driven, they usually only manage 35 - 50 watts/ch.

If you want more continuous power from all channels on 120 volts, you need to look at something like the Sunfire Cinema amps which are more like 90+% efficient thanks to Bob Carver's trickery. Or use 2 or 3 channel amps split up on multiple AC circuits. The big Cinepro amps (which use huge 3600 kva transformers) recommend running them on 240 volts (or a special 30 amp 120 volt circuit) if you want to get anything close to their full output power.

Yeah - I understand that. It also raises some interesting questions regarding the specification given and the FTC rules. I hope the Outlaws don't get too much trouble over that....

I'd love to see a time vs. clipping output diagram at 2, 4 and 8 ohms for a real production sample.


Charlie

"Power output: 200 watts RMS x 7 (all channels driven simultaneously into 8 ohms from 20 Hz to 20 kHz with less than 0.05% total harmonic distortion). 300 watts RMS x 7 @ 4 ohms (other conditions same as above)"

My problem is that this statement is misleading. 300x7 is 2100 watts, with 100 percent efficiency. At 120 volts, that's 17.5 amps, which most circuits won't support. Additionally, it's very doubtful that a test would support this assertion.

That doesn't mean that I think the amp is crap. On the contrary, I'd like to hear it. However, this is a misleading statement.

Maybe it really will try to suck 20+ amps out of the wall outlet in that circumstance. I wonder what its internal breaker is rated at? If 15A, then yes, the statement is definitely misleading.

Matthew: It probably does attempt to suck this power out of the wall. However, they also state that "Power consumption: 1,800 watts (maximum)". So, based on this, there's no way for it to produce 2100 watts (300x7). However, there's also little or no way for someone to ever draw that much power unless they have a set of inefficient, low impedance speakers and like to listen really loud.

I have a Creek 30 watt/channel amp that goes as loud as I care to go for two-channel, for both my Mirage (8 ohm) and Linn (4 ohm) speakers. 300 watts would be obscenely loud.

I just don't think that a company should be able to state, on the one hand, that maximum power is limited to 1800 watts, and yet, on the other hand, that the amp has a power output of 300 watts x 7 channels (2100 watts with 100% efficiency). There should be some type of disclaimer. Perhaps if you order the 220V version, you can get it to actually produce 300Wx7?

I wonder if the 220v version also states 1800 watts max draw.

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Matthew J. Hill
matt@idsi.net