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Real techie question for Amp-Knowers!

Discussion in 'AV Receivers & Amplifiers' started by Brad_Porter, Mar 13, 2003.

  1. Brad_Porter

    Brad_Porter
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    Right,

    I own a Denon 3802, an Arcam 3-Channel P-25 and 5 M&K 4-Ohm Speakers.

    I want the best power distribution to the front three. Easy eh? Let the Arcam power the front three while the Denon powers the back two! Yippee.

    BUT (regarding 4 Ohm loads)

    The Arcam only delivers 140W into 2 channels (is 100W into 8Ohms) but the Denon will do a proper job and double up to 210W into 4Ohms (105 into 8Ohms). This is in reference to 2 channel only!

    SO WHAT AM I ASKING???!

    Is it best to have the Denon powering just the front three and the Arcam powering the back two or vice versa?

    In reality, people would say that 'the power amp should power the fronts'. But the stats show that the Denon does a better job at increasing the current/power to the speakers (105w into 8ohms. 210 into 4Ohms) then the Arcam does (100w into 8Ohms, 140w into 40hms).

    I know that watts are not everything, but just to exercise the mind a little, how would you techies answer this question and what method would you choose for AV listening.

    Regards
    Brad
     
  2. nathan_silly

    nathan_silly
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    Arcam for front three, Denon for rears.

    Arcam will probably have a higher current rating, therefore more important than power output (watts) Since the front three reproduce most of the sound- use the Arcam for L/C/R.

    [edit] Regarding Denon output 210 w into 4 Ohm- no chance. Not for a cheap AV amp.
     
  3. sounddog

    sounddog
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    Brad,

    I would think the Arcam would be better for the fronts. but why don't you try both, and see what you prefer.

    What is technically best doesn't always turn out to be the best depending on circumstances. Just try both and whatever way round you prefer to listen to stick with that.

    There is no point in having all that kit if you do what we tell you whilst you are quietly thinking but I prefer it the other way round.

    Cheers

    Steff
     
  4. zaphod

    zaphod
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    I would suggest 3 points here

    1 Absolute power output is not relevant because unless you are using all the power available then it is the quality of the amp that is important. Power does not equal quality.

    2 Both amplifers will sound different. If the difference is too great then you will not get front to back integration. I have always had the problem that I could hear the difference in sound between the front and back speakers effectivly ruining the surround ideal for me. You will probably find that the best front to back integration is with the amplifiers one way round or using all the same amps for all channels.

    3 The Denon will probably be limited in power output when more than one channel is driven.

    Regards

    Zaphod
     
  5. lynx

    lynx
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    Spot on. You should read some of the threads on, in-car entertainment boards.These guys are largely living in fairyland with power figures they quote,but the worst thing is that they actually believe the p!$h that they sprout.
     
  6. MikeK

    MikeK
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    As has been stated already, it's which setup sounds best that's the important thing, not what some usually fairly meaningless paper specifications state.

    But if you are into "specs", consider this:


    The Denon is a fully featured integrated product, which on the face of it, delivers 7x105W full bandwidth into 8ohms, and it seems from what you are saying, 7x210W into 4ohms. It does all this, as well as powering all it's other circuits/display etc etc, and only consumes a maximum of 400W (probably around 560VA give or take).

    In 2 channel form, the P25 delivers 2x100W full bandwidth into 8ohm loads, from a max power input of 800VA. It has no other circuits or displays to drive, just the power amps.
    In 3 channel form, I suspect the output would be lower (I don't have the figures), but that would depend on several things (notably the power supply).


    However, hopefully you get the picture.
    Fair enough, there are differing designs, some offering higher efficiency than others (at least in power transfer terms), but no circuit ever devised can extract more power than is input to it. It simply isn't possible.
    In fact, no audio amplifier can even extract the same amount of power as is input to it - there are always some losses, mostly as heat and these can be a meaty proportion of the input too, but it depends on the design. One of the reasons that class D power amps are becoming more widespread (esp for subs) is their much higher power transfer efficiency, which means a much greater proportion of the input power is available at the output, which in turn means much less is wasted as heat (which is difficult to get rid of and can be problematic in terms of unit service life etc), but even these cannot produce more continuous power output than the amount input in the first place.


    BTW - this isn't a pop at Denon - all the major brands do a similar thing, and some are worse than Denon too!
     
  7. Brad_Porter

    Brad_Porter
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    Thanks guys - all be a great help......appreciate your replies....

    BTW, I chose Denon for rears and Arcam for fronts - does sound better and a nore 'even' sound.
     
  8. Reiner

    Reiner
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    The Denon is a fully featured integrated product, which on the face of it, delivers 7x105W full bandwidth into 8ohms, and it seems from what you are saying, 7x210W into 4ohms. It does all this, as well as powering all it's other circuits/display etc etc, and only consumes a maximum of 400W (probably around 560VA give or take).

    Also note the following:

    1. Most AV amps DO NOT deliver the quoted power into all channels driven simultaeneously. 7x105W means that each channel can handle 105 Watt max., but due to limitations of the power supply perhaps only when two are driven. Of course this would be at full load and usually is not practical or what we consider normal use. ;)
    I think in another thread here is was mentioned that the e.g. the Denon 3803 can only deliver 50Watt per channel if all channels are driven at the same time.

    2. Denon supposingly quotes average power consumption and not the max. power comsumption. Strange though.
    In any case you cannot directly conclude from the power consumption what is the max. output power though if the max is quoted it's safe to assume the amp cannot deliver more power than that (the max). See also MikeK's post.

    3. Power figures can vary a lot, depending how you quote (at what impedance, frequency and THD). There is IMHO no proper standard and manufactures make use of that, confusing or intentionally missleading the consumer. So beware!
     
  9. fraggle

    fraggle
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    A few things;

    First read this http://www.homecinemachoice.com/testbench/Amplifiers/Denon/DenonAVR-3802.php
    and note the two channels driven power figure of 138W at THD 1%.

    Which is fairly impressive for an amp rated at 105WPC.

    Also the "an amp cannot output more power than it consumes" is rubbish. It can produce peaks of power far in excess of the rated mains consumption, the "burst" of power comes from the reservoir capacitors in the PSU, thats the main reason they exist.

    *Constant* power, yes, what is said is true, but I for one don't listen to white noise at reference level! :)

    I've noticed the Denon can sound a bit "out of breath" in movie scenes where there's a lot of action going on (xXx drug camp fight scene for example), which will be the PSU being unable to keep up with the demands on it, but heck, its a £500 7 channel amp! Cheap as chips! :D
     

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