Receiver Total Output Power

Debugger Unregistered guest	Posted on Monday, July 05, 2004 - 06:25 GMT Hi All, I cannot figure out this one - how can a receiver consuming 180 Watts managed to output 600 Watts (5 x 100W + 1 x 100W)? If it can create power, the our energy crisis is over!! ... David
landroval Silver Member Username: Landroval Post Number: 337 Registered: Feb-04	Posted on Monday, July 05, 2004 - 07:44 GMT No it cant, sorry Advertised power and real power are two different things. If max consuming is 180W then your receiver wont be able to output 100 Wpc continuously, but it can do it for a short time, or to one channel continuously.
Debugger Unregistered guest	Posted on Monday, July 05, 2004 - 12:35 GMT I see, much like a timing sharing scheme; but then with 6 channels, the time lapse between each output would produce gaps in the output. Wouldn't it? It the time lapse is far enough, I suspect we can hear it. Thanks for the insight.
J. Vigne Unregistered guest	Posted on Monday, July 05, 2004 - 16:26 GMT What the amplifier draws as wall current has no relationship to the wattage it can output. It is Ohm's Law in effect. How much power do you think a 60 watt light bulb produces? Put Ohm's Law into a search engine for more information.
Chet New member Username: Cszy67 Post Number: 10 Registered: Apr-04	Posted on Monday, July 05, 2004 - 21:57 GMT Here is some useful reading with regards to power: http://www.nadelectronics.com/power/index.htm
Debugger Unregistered guest	Posted on Tuesday, July 06, 2004 - 05:37 GMT Since the amplifier is not producing energy and efficiency is always less than 100%, then what it draws will in effect be the limiting factor for the output. Ohm's law, in this case does not play a part in the explanation. I believe landroval's explanation is the most plausible one. My receiver draws 180 watt and will not be able to produce more than (at 60% efficiency) 18 watts per channel continuously on all channels. Since amplification rides on top of the sine wave envelope, each channel at an given time will be demanding different modulation; thus it is possible for one or may be two channels to produce 100 watts each for a short period of time. Or, at least till the circuitry decided that the distribution should be done otherwise.
landroval Silver Member Username: Landroval Post Number: 339 Registered: Feb-04	Posted on Tuesday, July 06, 2004 - 11:41 GMT Amplifiers have power reserves stored in capasitors and that power will help to output more power in a short period than what it draws from the wall. When the capasitor will be empty the amp relies only to the transformer and that is the maximum continuous power that it can output. Of course the amplifier transistors will limit the max output also, but more often the transformer is the weakest link.
Debugger Unregistered guest	Posted on Tuesday, July 06, 2004 - 14:21 GMT That's very true and vendors often times skim on power conditioning to get more thru put. Well, I appreciate all the posts to my question. Take care,
Debugger Unregistered guest	Posted on Tuesday, July 06, 2004 - 14:22 GMT That's very true and vendors often times skim on power conditioning to get more thru put. Well, I appreciate all the posts to my question. Take care,
J. Vigne Unregistered guest	Posted on Tuesday, July 06, 2004 - 16:16 GMT You are not understanding Ohm's Law in this case. The amplifier is drawing wall current at a very low input resistance. It is then outputting power into a substantially higher reistance. The example of the light bulb should be sufficient to clarify this situation. You cannot drive a loudspeaker with the current a 60 watt bulb draws but it is rated at 60 watts due to its filament resistance. If you had a sixty watt amp it would provide sufficient power to drive almost any speaker. Because its power is calculated into a higher resistance. Amplifiers have the ability to store energy in their power supply capacitors, that is a reason for the substantial cost of a high end amp. It is expensive to build a good power supply. If you are building your design knowing it will have to draw current from the wall to meet dynamic conditions you are designing the worst of audio equipment.
John A. Gold Member Username: John_a Post Number: 1654 Registered: Dec-03	Posted on Wednesday, July 07, 2004 - 06:06 GMT I think Debugger has good point, Jan. You can store energy in capacitors, but you can't make it. In a steady state (equals "continuous" - and why we should look for that word in power specs), the power (rate of energy use) out cannot possibly exceed the power (rate of energy use) in. That applied just as much to a light-bulb, or anything. "What the amplifier draws as wall current has no relationship to the wattage it can output" No, but what it draws as wall power certainly does, and I think that is Debugger's point. Current is different. You can do anything you like to current: for example increase current by decreasing Voltage. Power (in Watts) = Potential difference (in Volts) x Current (in Amps). Chet's link is very good. The real answer is that some makers care more about getting numbers on paper than about making an amp that can drive speakers so they sound good.
J. Vigne Unregistered guest	Posted on Wednesday, July 07, 2004 - 16:35 GMT No one is arguing that many, many manufacturers make lousy equipment and pass it off to an unsuspecting, uneducated clientelle. That has been going on since the beginning of audio amplification in the home. That was the reason, back in the 1970's, that the FCC passed the regulations that were intended to put a stop to measurements like E.I.A. (more or less the equivalent of Everything I Assume) power ratings of 200 watts peak power for a 12 watt R.M.S. Emmerson console. But, as in all regulations, there are those who will seek the loophole to make easy money. But your article only addresses the way a well build amplifier should rate its output wattage, it has nothing, really, to do with how an amplifier's power supply operates. By your logic since the amp is drawing AC power from the wall that AC voltage is the only thing that exists within a power supply and the amplification stages. I think you all feel that the AC that comes from the wall outlet is then transfered unchanged throughout the amplification stages to emerge at the speaker outputs. The first thing that happens as the voltage enters the power supply is the conversion (rectification) of AC to DC. This DC voltage is then used throughout the amplification stages until it is once more converted back into an AC voltage to drive the loudspeaker. During its traverses through the various stages of the drivers and amplifiers it is stepped up in voltage through the use of various devices that, in a tube amplifier, result in internal voltages up to 850 volts DC though the wall outlet can only provide 120 volts AC. The very function of the amplifier, by defintion, is to step up the voltage from the source to the speakers. How this is done is the art of designing a good circuit. Does every manufacturer design good circuits? Obviously not. Do some manufactueres design circuits just good enough to keep them out of litigation? Yes, far too many. But, I repeat, "What the amplifier draws as wall current has no relationship to the wattage it can output". That may be overstating the case slightly but if you will understand the operation of the various gain stages in an amplifier you will see it is more true than not. This is particularly true in the modern era of IC circuits where numerous devices can be paralleled to give higher gain and lower output impedance. These are fragile circuits that ride the razor's edge of stabilty and make a mockery of linearity, but, if your goal as a designer is to build for a piece of paper instead of the real world it is the most expedient course of action. So we agree that Chet probably has a piece of junk for an amplifier but not on how it develops its power. I would suggest that a call to a manufacturer to ask how an amplifier is designed will solve this problem.
John A. Gold Member Username: John_a Post Number: 1658 Registered: Dec-03	Posted on Wednesday, July 07, 2004 - 17:20 GMT Jan, Thanks. As usual, you are way ahead of most of us in understanding what goes on between the wall socket and the speakers; I always learn from your posts. But I think Debugger's point was simple, and correct. You cannot get more continuous, time-averaged (steady-state) Watts out, than you put in. In fact, it has to be less. It is a basic physical law (1st and 2nd laws of themodynamics), in the science sense, not a prescription. If there were known exceptions they would overturn everything anyone knows, which of course is not impossible (it happens), but the world would be an even wierder place than it already is. Not to mention you could get energy from nowhere, and all power generation systems would become instantly obsolete. Patent offices for years have looked at all sorts of crazy schemes for defying thermodynamics. None work, and the best guess is that none ever could. I don't think there is real disagreement on this, with respect.
KEGGER Silver Member Username: Kegger MICHIGAN Post Number: 732 Registered: Dec-03	Posted on Wednesday, July 07, 2004 - 17:35 GMT i had a whole big post going about different gain curcuits and power supplies and how some react different than others so obviuosly you will get different end results.so there is no rule of thumb! but somehow the darn page disapeard. anyways yes you would have to have some extremly efficent curcuits to get 100watts for 6 channels out of 180watts drawn."not gonna happen" but depending on the type of curcuit and or power suplly along with how much distortion you want. you can make more current than you draw. "amplify" but are you going to get 600 from 180 not likely. back in the day you use to be able to take a 2 channel amp and divide it's current draw in half and be reasonably close to it's power output per channel. (8 ohm) but that just isn't so anymore. a quality audio curcuit will usually draw more than it outputs though.

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