Power rating ?

Discussion in 'AV Receivers' started by RyanJE, Feb 1, 2005.

  1. RyanJE

    RyanJE Second Unit

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    Ive heard people talk about pure/clean watts. I was wondering what are the differences between power ratings. I ask because im looking to buy a new avr. Some Harmon's are rated at 55xN and other brands are 100-130xN, how can this be. Any good links or articles.
     
  2. Justin_D

    Justin_D Stunt Coordinator

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    Simply put, some Harman Kardon recievers have different and better amps than others.

    When people say "clean" or "pure" watts, what they means is what a reciever REALLY puts out as opposed to what they SAY they put out. For instance, some lower end Sony recievers (non-ES line) claim to put out 100 watts into 6 channels with 8 ohms resistence. In actuality it is closer to 35 watts/channel CONSTANT. 100 watts is really with 1 channel driven into 1 khz. When in a movie is only 1 channel playing at a single frequency? Never.

    Also, H/K are usually underrated. Some more than others, but you can trust that you are getting the wattage they promise.
     
  3. RyanJE

    RyanJE Second Unit

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    I wonder that. I have speakers that are rated 50-200 watts and I have to crank my sony str-de595 way up to get decent volume. How can you tell before purchasing if your getting clean watts or not.
     
  4. Tingwe

    Tingwe Stunt Coordinator

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    case in point. my pio 1014 has 110watts per channel x 7 on the box and on the pioneer website, but has been tested to go 115 watts ALL-channels driven. give it a try. [​IMG] you also can't go wrong with the HKs, they di underrate their power all the time.
     
  5. Jose G

    Jose G Supporting Actor

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    Ryan, you should take a look at this link from the HT Primer. The primer is full of great info.

    José
     
  6. RyanJE

    RyanJE Second Unit

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    I dont fully understand what THD is after reading the primer, r what to look for. Heres the same model I have only in 6 channel mode...

    ---STR-DE597 User Manual (2.03 MB)

    • 6 Channel Power Rating: 100 Watts Per Channel x 6 (8 ohms 1 kHz, THD 0.7%)
    • Stereo Power Rating : 90 Watts Per Channel x 2 (8 ohms 40 Hz-20 kHz, THD .09%)

    What does this all mean and why is stereo power rated from 40-20khz?
     
  7. Kent Y

    Kent Y Auditioning

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    Regarding the stereo frequency range, the amp obviously couldn't push enough power to drive the lower ranges (20-40Hz) at 90 watts, so rather than list the full range wattage, Sony cut down the range. There must have been a big drop off for the lowest frequencies. 100 watts is the holy grail for many of the lower end mass market receivers, so they try to do everything they can to put that number on the box. Notice even the 90 watts is into 6 ohms. And, while the 100wpc in 6-channel mode is into 8 ohms, it was only measured at 1kHz, and the THD is very high at 0.7%. Very possibly with only one channel driven as well; certainly not with all six.
     
  8. Jose G

    Jose G Supporting Actor

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    THD =Total Harmonic Distortion
    Basically the amplifier outputs an amplified version of the input signal, right? Right. But, it also adds any distortion created by the amplifier. All amplifiers and signal processors add distortion to the signal, so this is a way to rate the distortion. Now can we hear the differences? There are many factors that contribute to this and you can make yourself nuts trying to figure it all out. But do a search on the web for "Total Harmonic Distortion" and you will see what I mean.
     
  9. John S

    John S Producer

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    For a good idea, on non-digital amps is simply look at the rating of what it pulls from the wall.


    Example:

    6 x 100 watts, the back of the AVR should be close to 1000watts to truly provide that.

    If you look though, many of them will state like 280watts, the laws of physics just don't work out at all on that.


    I have no experience with the newer "Digital amps", but as I understand it, they require much less from the wall to provide the same sort of power to the speakers.
     
  10. RyanJE

    RyanJE Second Unit

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    I did notice that. It seems like the high end avr's are taking about 500 watts to run in 100x7 or 6 and my cheapo avr only uses 240 watts. Man do you guys have the upgrade bug too. I keep finding things I want everyday on this forum. Its killing me.
     
  11. Shiu

    Shiu Second Unit

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    You cannot always go by what the back of the AVR says. It may say 300VA or 280W but it does not say under what condition. It could be for typical (whatever that means)listening level, 2 channel at rated output, or whatever.

    It seems that some manufacturers tend to inflate their output but deflate their input power to show that they are energy efficient. HK is one exception, they tell you their power requirement at both idling, and with all channels at maximum output.
     
  12. RyanJE

    RyanJE Second Unit

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    Shiu, we were talking about the amount of power uptake the receiver uses. Not the actual per channel rating. Jon was basically stating that it would be hard for an avr to push 100x6 when its only using 240watts to operate at peak.
     
  13. John S

    John S Producer

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    Yes, most wattage ratings on the AC side are maximum and stated as such. 300VAC still makes my point as well, you can't get 6 100watt channels out of it.

    Interesting, an AVR like an H/K will be like nearly 900 watts of the AC side, and be rated 55watts per channel, just as an additional example of this.

    I was sort of hope'n more information on efficiency of the newer Digital Amps and exactly the how/why would have materialized out of the Digital Amp thread. I really don't know much about it. But I have designed and built a few amps over the years being an electronics sort of tinker type, and what I'm saying about AC -vs- Actual power output on the Audio side is really true. It's a little better these days, but basically you get 1/2 of that AC power, and the rest is dissapated as heat.
     
  14. Shiu

    Shiu Second Unit

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    Ryan,thanks, but I knew what John was talking about. I am saying that the power consumption (power taken in by a receiver)figures at the back of a AVR do not always mean it is the power consumption when all channels are delivering their maximum rated power.

    Actually, I am not the one who say this, I read this from sources like audio magazines. If it is true, what it means is that an AVR that specifies say power consumption of 300VA, or 300W does not necessarily mean that is the maximum consumption. It may consume much more than that when all channels are deliverying its rated power.

    Until we are sure that those specified power consumption figures are in fact maximum, i.e. the power supply is at it limit, we cannot say those specifications defy physics. Conversely, if those numbers are in fact "maximum", then I would agree with John S completely. No AVR can put out more than what it takes in. In most cases, they do good if they can put out 70% of what they take in.
     
  15. Shiu

    Shiu Second Unit

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    John, read your post after I posted mine. Of course you are right if those numbers on the a.c. side are "maximum". I think some designs could exceed the 50% you stated, at least for short duration. As long as the amp section is sound, most power supplies can handle more in terms of say an one hour rating as opposed to continuous. Transformers generally have excellent overload capacity.
     
  16. Kevin_F

    Kevin_F Stunt Coordinator

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    So what is the best way to find the actual amount of power that each receiver is putting out?

    I want to get a receiver that gives me 100W x 7 or as close to that as possible, and of course is within my budget.
     
  17. John S

    John S Producer

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    Real test reports are the best indicators, certainly not published specs. My Denon 4802 says 1200watts max on the AC side by the way. 7.1 AVR, 7 high current amps inside.

    But I still say, from my example on non-digital amps, you can certainly get a better idea of it.


    Sheeesh, I'd think it against the law to under rate maximum power draw on the AC side. But nothing surprises me anymore, that's for darn sure.
     
  18. Shiu

    Shiu Second Unit

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    I am sure the 4802 is a very powerful AVR. If you look at its little brother, the AVR3805 has its power consumption specified like this:
    Power supply 120V 60Hz
    Power consumption 7.1A, no mentioning of the word maximum.

    120V X 7.1A = 852 VA. Assume a power factor of 0.8 (it has to be less than 1), Power (Watts) = 120 X 7.1 X 0.8 = 681.6W. So if efficiency is 0.5, you would get 340.8W, or 7 X 48.7W total amplifier output.

    According to H.T. mag lab measurements the 3805 did 5 X 114.9W at 0.1% THD, or 5 X 125W at 1%. It did 243W X 2 at 4 ohms.

    According to S&V mag lab measurements, the 3805 did 7 X 93W.

    None of those numbers support the specified 7.1A consumption, or 852VA being "maximum". This gets even more dramatic if you look at some of the Sony ES, or DB receivers that were tested to do close to 7 X 90 or 7 X 100 yet their specified power consumptions are like 370 VA, 340 W etc. I agree mathematically (or in terms of physics) this does not make sense, unless those quoted power consumption numbers are not really "maximum".

    I used to own a Sony DA4ES. Its power supply transformer looks quite large, and the receiver weighs 46 lbs (almost 10 lbs heavier than the 3805) yet its power consumption was a mere 390 VA.

    One more point, H.T. mag tested both the HKAVR630 and the 3805 in the same Nov 04(I think) issue. The 3805 was tested to have more power in 1,2,&5 channels than the 630, especially into 4 ohms. The 630 specifies a much higher power consumption than the 3805.

    So John, I agree with you in general, but I think there are many exceptions.
     
  19. John S

    John S Producer

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    I believe you.. I just think it should say something like nominal. You have me curious on my 4802.

    Just interesting more than anything. So basically neither spec really means a darn thing!!!! I can accept that. [​IMG]
     
  20. RyanJE

    RyanJE Second Unit

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    Its a damn shame theres no industry standard with this kind of thing. The uninformed (willingly or not) are getting shafted. AS was I when I purchased my AVR, now I found myself searching for a new one.
     

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