#29603 - 10/26/05 07:30 PM
Re: Is this Clipping?
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Gunslinger
Registered: 09/04/05
Posts: 15
Loc: Central Florida
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Originally posted by tonydeluce: There is no way the 770 can drive 300 watts into 7 channels. That would be 2100 watts assuming power supply could even hand it...
I bet four monoblocks for your surrounds and bi-amping your front, center, and right, speakers with the 770 would ROCK! Uh, the monoblocks put out 300W into a 4 ohm load (same as the 770)... 300 * 4 is 1200W... but the amps are about 50% efficient, so 4 monoblocks will require 2400W from the outlet. So I guess there is no way 4 monoblocks will drive his 4 surrounds either, using your logic. So I am willing to bet that 4 monoblocks will not provide 1 iota of benefit. -T
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#29604 - 10/26/05 07:53 PM
Re: Is this Clipping?
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Gunslinger
Registered: 07/25/04
Posts: 90
Loc: USA
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Interesting analysis. However, you are assuming that all 4 monoblocks are in the same outlet. In that case I would agree with you. Obviously, if they were on a different circuit then some benefit might be achieved.
Although, I must admit my curiousity is stirred. How could the 770 put out 2100W if it is only drawing 1800W maximum? Now bear with me, but if the total capacitance is sufficient then for some short time [t] with t<120ms [ milliseconds ] then it is possible for the 770 to do that. However, I believe if [t] is some long time in comparison say 10 seconds, then something would have to give. Of course, 10 seconds of a very high signal level in all 7 channels at the same time....not that much chance of happening.
Just my 2 cents worth, and I am probably missing something as well. Perhaps Gonk or Soundhound could help me out here?
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#29605 - 10/26/05 08:05 PM
Re: Is this Clipping?
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Gunslinger
Registered: 09/04/05
Posts: 15
Loc: Central Florida
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Bob045,
I was using the same logic as tonydeluce, so I believe there was no mention of separate outlets.
-T
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#29606 - 10/26/05 08:30 PM
Re: Is this Clipping?
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Gunslinger
Registered: 10/16/05
Posts: 45
Loc: Southern California
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You are assuming you have to plug everything into the same circuit :-)
_________________________
Samsung 61in 1080p DLP Denon 4306 ( pre/pro only ) / Toshiba HD-A1 Cinenova Grande ( 600W x 3 ) - Polk LSi15s, LSiC Outlaw M2200s ( 300W x 2 ) - Polk LC265i x 2 Velodyne HGS-15X
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#29607 - 10/26/05 08:40 PM
Re: Is this Clipping?
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Desperado
Registered: 07/03/05
Posts: 547
Loc: NJ/Beijing
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Even separate outlets are often on the same circuit in the same room (unless you've specifically set things up differently).
Clearly, the 770 can't provide full output to all channels @ 4ohms simultaneously and continuously. There just isn't enough juice to go around. I suspect that it probably can't do it at 8ohms either when you consider that the amp isn't anywhere near 100% efficient so you're losing probably 30-40% of the power as heat.
Anyone from Outlaw care to comment? Is my math faulty?
Cheers,
_________________________
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#29608 - 10/26/05 09:05 PM
Re: Is this Clipping?
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Gunslinger
Registered: 10/16/05
Posts: 45
Loc: Southern California
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That is why I said separate circuits. I had two completely isolated 15 A circuits installed and I use three separate circuits for powering my A/V components.
I doubt it could do even 1400 watts ( 7 channels into 8 ohms ) for more than a very brief period.
Unless you are listening at close to reference levels driving all channels you should be o.k.
But if you are using six or more 4 ohm speakers, forget about it, as they say :-)
_________________________
Samsung 61in 1080p DLP Denon 4306 ( pre/pro only ) / Toshiba HD-A1 Cinenova Grande ( 600W x 3 ) - Polk LSi15s, LSiC Outlaw M2200s ( 300W x 2 ) - Polk LC265i x 2 Velodyne HGS-15X
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#29609 - 10/26/05 10:06 PM
Re: Is this Clipping?
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Desperado
Registered: 12/29/02
Posts: 358
Loc: Central VA
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This can happen because the outlet and more specifically the circuit breaker are NOT current limiting devices (except for a short circuit). The breaker works on a thermal trip function which means it will take many, many times it's current rating and still not trip as long as the time at the increased current is not to long. Most breakers will operate at 120% of rated current indefinitely and 500% of rated current for many seconds. Some seem to feel that the breaker somehow begins to inhibit the flow of electricity as soon as the amperage rating is met and abruptly cuts it off right above the 1800-watt rating of a 15 amp breaker, this is just false. Look at it this way the same 15 amp breaker used in Europe would have a "wattage" rating of 3600 due to the increased voltage. Another fallacy seems to be that a 20A breaker somehow flows electricity easier than a 15A breaker .... it won't. Breakers are also not prone to wear and have a lifetime in the thousands of thermal trips. They work on the same principal as the turn signal blinker in your car to the extent they both use bimetal to open a circuit. I'm not inventing this or even claiming some superior expertise, anyone can read the same articles from Square D or Cutler-Hammer that explain the operation of a circuit breaker.
Capacitors in the power supply are also there to help with the momentary demands.
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#29610 - 10/26/05 10:18 PM
Re: Is this Clipping?
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Gunslinger
Registered: 09/04/05
Posts: 15
Loc: Central Florida
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I don't think it can put out the power specified because the home's outlet is limited. This thing really needed 2 power cords, one to each power supply. This review ( http://ultimateavmag.com/amplifiers/147/index4.html) had 6 channels driven at the same time, for a total of 221W x 6 into 8 Ohms (1 KHz), and 347W x 6 into 4 Ohms (1 KHz). The test bench could only handle 6 channels. The variac saturated, and then blew a fuse (on the variac). For 4 Ohms x 6, it put out 2082W... so it drew probably about 4000W from the source. -T
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#29611 - 10/26/05 10:34 PM
Re: Is this Clipping?
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Gunslinger
Registered: 10/16/05
Posts: 45
Loc: Southern California
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If it put out 2082 it was for a very very brief period of time...
_________________________
Samsung 61in 1080p DLP Denon 4306 ( pre/pro only ) / Toshiba HD-A1 Cinenova Grande ( 600W x 3 ) - Polk LSi15s, LSiC Outlaw M2200s ( 300W x 2 ) - Polk LC265i x 2 Velodyne HGS-15X
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