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  1. #1

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    Default Understanding how a Recevier powers speakers

    I was doing some thinking on how a/v receviers said to be 7.1 or like and claim that they do 110 watts per channel, but when all channels are driven its more like 40-60 rms. What is causing that drop. Is it too weak of a power supply or just inefficent amplifiers? Does the receviers amp make a lump of power and each channel pull what it needs. I am just having a hard time grasping how it can be rated at one thing while only one channel is driven but when more channels are driven its actually be much lower. It sound to me like the power supply isnt that great.

    I recently removed my mains from my Pioneer Elite, but my center and surround is still powered off of my Elite. Did I free up enough "headroom" so to speak to power my center and surrounds at higher volumes then previous? I watch alot of blu-ray concerts and the Center channel gets used alot more then the mains. Now that mains have more juice then i could ever use, will I run the risk of clipping the center at high volumes? Does the rear surrounds (t-15) really place that much of a draw on the receiver?

    I hate not having some kind of indicator of where my amp is in relation to its max output. My 1.0t has indictors that make it a little easier. Not that i trust them 100% but its a good ball park.
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  2. #2

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    Is it too weak of a power supply
    Bingo!
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    Jesse's got you there!

    What's that Pioneer weigh? I think less than 29 lbs? Let's compare your Pioneer AVR with a two channel vintage receiver from the early '80s that I own. The Pioneer SX-3900 weighs in at about 45 lbs. and only has 2 channels. It outputs a real 120 watts x 2 into 8 ohms. It has one rather "large" and heavy toroidal transformer and two large storage capacitors which account, I bet, for at least half of its weight.

    The average 200 watt x 2 power amp probably has a minimum of 50-60,000 mfs of storage capacitance and a monster toroid or two as well, along with other members in the supporting cast.

    Although weight and size is not the end all and be all of power. They are a factor in most A and A/B amps.

    cnh
    Last edited by cnh; 02-25-2012 at 07:54 PM.
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    Quote Originally Posted by cnh View Post
    Jesse's got you there!

    What's that Pioneer weigh? I think less than 29 lbs? Let's compare your Pioneer AVR with a two channel vintage receiver from the early '80s that I own. The Pioneer SX-3900 weighs in at about 45 lbs. and only has 2 channels. It outputs a real 120 watts x 2 into 8 ohms. It has one rather "large" and heavy toroidal transformer and two large storage capacitors which account, I bet, for at least half of its weight.

    The average 200 watt x 2 power amp probably has a minimum of 50-60,000 mfs of storage capacitance and a monster toroid or two as well, along with other members in the supporting cast.

    Although weight and size is not the end all and be all of power. They are a factor in most A and A/B amps.

    cnh
    Not only that but that power is shared by 7 channels, audio and video processing in avrs
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    That's right. There is, in most cases, no separate power supplies for all of that in most AVRs. So what a load of work you have a fairly light-weight unit performing.

    cnh
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    The weight of any AVR tells you how it's made. Or what the watts are about, BS vs Real.

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    Weight of the unit is a big deal to me. My a753 Carver goes around 70lbs...and it's big. It also has a nice bank of HUGE output caps.(23000 micro farads...each?)
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    Quote Originally Posted by ibewbrother View Post
    Weight of the unit is a big deal to me. My a753 Carver goes around 70lbs...and it's big. It also has a nice bank of HUGE output caps.(23000 micro farads...each?)
    You comparing a power amplifier to an AVR, why?

    23000uF is a very large cap. However, lots of smaller caps are preferred because they are faster than large ones.

    BTW, I believe your amplifier weighs closer to 40lbs.
    'Political Correctness'.........defined

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    Quote Originally Posted by F1nut View Post
    23000uF is a very large cap. However, lots of smaller caps are preferred because they are faster than large ones.
    I think this is an audio engineering myth.
    It only makes sense if the residual inductance (of the smaller capacitor) per uf is less than that
    of the larger capacitor, which is usually not the case (at least when comparing capacitors of
    the same construction type).
    I assume we're not talking about something implausible like 1000 10uf film caps replacing one
    10,000uf electrolytic here.
    ... and in fact, if you put many small capacitors close together on the board with the same orientation,
    you can increase the residual inductance and make the array worse (slower) than the single bigger one.
    Last edited by cristo; 02-26-2012 at 05:58 PM.
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    I favor the class D amps, which weigh in alot less and sound great. A slightly different ball game than conventional amps.
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    Quote Originally Posted by cristo View Post
    I think this is an audio engineering myth. .
    I wouldn't go that far. There's more to it than size or number of caps. But if size is any indication, look at the bigger caps in older receivers and the smaller more numerouse ones in todays. Older receivers have rounded, somewhat flabby low bass while todays receivers can dish some well defined fast low end. Of coarse all that can't be contributed to caps alone but I'm pretty sure it helps.

    Design has alot to do with it, god knows there has been excellent built pieces in the past that still sounded like garbage becouse of poor design, so on that aspect I can agree. Stranger crap has happened in this hobby for sure.

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    +1 cristo
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    Quote Originally Posted by specd_out View Post
    I recently removed my mains from my Pioneer Elite, but my center and surround is still powered off of my Elite. Did I free up enough "headroom" so to speak to power my center and surrounds at higher volumes then previous? I watch alot of blu-ray concerts and the Center channel gets used alot more then the mains. Now that mains have more juice then i could ever use, will I run the risk of clipping the center at high volumes? Does the rear surrounds (t-15) really place that much of a draw on the receiver?

    I hate not having some kind of indicator of where my amp is in relation to its max output. My 1.0t has indictors that make it a little easier. Not that i trust them 100% but its a good ball park.
    I think you're fine the way you have it. That AVR has plenty of power to run your remaining three speakers. You do have another pair of indicators - your ears. They'll bleed before you damage that center. JMHO, of course.
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    With a conventional Class A or AB amplifier design, you have to remember the laws of physics.

    From my experience, a 62lb. AVR sounded much better than a lighter unit that is also Class A or AB.
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