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Discussion Starter · #1 ·
If I connect a separate power amp to the front pre-outs, will the receiver divert unused power from the fronts to the other main outs?


I'm thinking of increasing the size of my front speakers and have an unused 2 channel Adcom power amp. Wouldn't using the above described connection at least decrease the load on the power supply? I'm just not sure whether or not these new receivers are able to redistribute unused power to the speaker outs of the other channels. Is that clear?


(I thought I read somewhere that you would get some increase, but not full current from unused output channels.)


Thanks
 

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a) technically speaking, yes, by reducing the needs placed on the power supply, you'll make more current available to the amplification paths that are still being supplied by it... will it "divert" it? i don't believe that in the amplifier in question that there are multiple power supplies, so "divert" is the wrong word. the two unused amplification paths just won't be demanding any power.


b) "bigger" speakers don't necessarily require "more power"...
 

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Quote:
Originally Posted by dhoover /forum/post/17041285


If I connect a separate power amp to the front pre-outs, will the receiver divert unused power from the fronts to the other main outs?


I'm thinking of increasing the size of my front speakers and have an unused 2 channel Adcom power amp. Wouldn't using the above described connection at least decrease the load on the power supply? I'm just not sure whether or not these new receivers are able to redistribute unused power to the speaker outs of the other channels. Is that clear?


(I thought I read somewhere that you would get some increase, but not full current from unused output channels.)


Thanks

By all means do so. The L-R channels present the biggest load and will benefit greatly from a real amp. The question of whether the other channels benefit is secondary, but yes they do.


You do also raise the question of whether the new fronts are a good voice match for the rest, which should be the 1st consideration.
 

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It's pretty simple. All amplifiers are drawing power from the power supply filter caps which are being charged directly from the power supply transformer. Charging is somewhat complicated by the fact that it's AC current coming in and through a bridge rectifier.


Just think of it as some really quick dude taking trips back and forth from the transformer to the caps carrying electrons, if that helps



The more amplifiers you have speakers hooked up to, the faster the filter caps are being emptied of their energy.


A bit oversimplified, but as you hook more speakers up, you divide up the power that can be supplied.


You can pick up a relatively cheap Kill A Watt meter, about $30 to $40 I think, and see this in action. Disconnect a speaker while the system is playing and the reading on the Kill A Watt will drop.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by ccotenj /forum/post/17041360


a) technically speaking, yes, by reducing the needs placed on the power supply, you'll make more current available to the amplification paths that are still being supplied by it... will it "divert" it? i don't believe that in the amplifier in question that there are multiple power supplies, so "divert" is the wrong word. the two unused amplification paths just won't be demanding any power.


b) "bigger" speakers don't necessarily require "more power"...

Yes, understood. Divert was a poor choice of words. So it's really about total current from a power supply?


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Discussion Starter · #6 ·

Quote:
Originally Posted by rdgrimes /forum/post/17041387


By all means do so. The L-R channels present the biggest load and will benefit greatly from a real amp. The question of whether the other channels benefit is secondary, but yes they do.


You do also raise the question of whether the new fronts are a good voice match for the rest, which should be the 1st consideration.

Thanks for all replies. I'm doing a step by step upgrade. I'm considering a complete 7.1 speaker replacement first (possibly Aperion). I was hoping that using the 2-channel power amp for the fronts would let the Yamaha "breathe" a little easier. (I see Emotiva in my future.)


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Discussion Starter · #7 ·

Quote:
Originally Posted by MichaelJHuman /forum/post/17041411


It's pretty simple. All amplifiers are drawing power from the power supply filter caps which are being charged directly from the power supply transformer. Charging is somewhat complicated by the fact that it's AC current coming in and through a bridge rectifier.


Just think of it as some really quick dude taking trips back and forth from the transformer to the caps carrying electrons, if that helps

Yes, got it. So theoretically transient response would benefit because the "quick dude" might not have to make as many trips, right? Great analogy.
 

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Failure to track the input signal would result in distortion. Distortion, by definition is any deviation between the input and output waveform. Other than the difference inherent in making it many times "bigger".


If an amplifier could not respond fast enough to "track" the input signal distortion would result.


This could result from a low slew rate. Slew rate measures how fast an amplifier can alter it's output voltage.


As to whether slew rate is a common problem, I don't know. I would think real life audio signals are pretty slow compared to the speed of an amplifier, but I am guessing.
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/17043314


Failure to track the input signal would result in distortion. Distortion, by definition is any deviation between the input and output waveform. Other than the difference inherent in making it many times "bigger".


If an amplifier could not respond fast enough to "track" the input signal distortion would result.


This could result from a low slew rate. Slew rate measures how fast an amplifier can alter it's output voltage.


As to whether slew rate is a common problem, I don't know. I would think real life audio signals are pretty slow compared to the speed of an amplifier, but I am guessing.

My guess is that speakers are far more likely to fail in responding fast enough, especially with some of today's high-res audio. To that end, a higher power amp will provide more accurate control of the speaker drivers and a "cleaner" perceived sound. At least that's been my experience.
 

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I have read assertions that damping factor can affect the ability of an amp to control speakers. One article on was from Audioholics. I know some people have questioned it. I don't know enough about the topic to critique their math

http://www.audioholics.com/education...ystem-response


I don't know how power factors into it other than just having enough power to avoid clipping. Some people talk about higher current amplifiers having some ability to be "faster" or whatever.


As long as a power supply can hold the voltage high enough to avoid clipping, I thought all was well. When I look at benchmarks with a single channel driven, amps can put out very high power without clipping which means their nominal rail voltage is pretty high. For example on my 3900, rail voltage is 70 volts. That's never going to be the limiting factor in normal use. The limit will be excessive demand on the power supply causing the rail voltage to drop such that clipping is occuring.


If you have any links explaining how higher power regardless of clipping helps control speakers better, I would be interested.
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/17044448


If you have any links explaining how higher power regardless of clipping helps control speakers better, I would be interested.

Purely my own experience, and perhaps common sense. Speakers are mechanical and rely on the amp to control their movement. More power = more control. By design, speakers are fairly bouncy in their excursion. Seems to me that more power means less of that. More power means the driver surface can return to center faster, reverse direction more smoothly, etc. All of which should translate to a cleaner sound, which has been my experience.


In any case, for this OP the addition of an amp even for the mains will be a very good thing. I am pretty certain that the 665 is clipping even at modest volume levels with 7 channels driven. But I'll add that I have never used my 665 with more than 2 back surround channels driven.
 

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Quote:
Originally Posted by rdgrimes /forum/post/17044642


Purely my own experience, and perhaps common sense. Speakers are mechanical and rely on the amp to control their movement. More power = more control. By design, speakers are fairly bouncy in their excursion. Seems to me that more power means less of that. More power means the driver surface can return to center faster, reverse direction more smoothly, etc. All of which should translate to a cleaner sound, which has been my experience.

Except that speakers draw power based on their impedance, and the voltage level at the output of the amplifier. A higher power amplifier does not "drive" more "power" into the speaker at a given listening level. It is simply capable of delivering more power when it is demanded - increasing volume to increase the listening level, or to handle dynamic peaks.


Lower impedance speakers draw more current from the amplifier and are thus more difficult to drive without browning out the amp. Higher power amps are generally better capable of dealing with low speaker impedance.


That said, more power is still generally better because it is more forgiving of speaker load and makes clipping on peaks or at high listening levels less likely.


Now, AVR's are generally rated with only two channels running. There is not enough power supply current to power all channels to rated output simultaneously. So using an external amp for the front channels will relieve that drain on the power supply and allow it to run the other channels closer to their rated output. But it will not allow them to run over their rated output. It will still be less because you are running more than two channels at a time.
 

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Quote:
Originally Posted by NAD Paradigm /forum/post/17044713


Except that speakers draw power based on their impedance, and the voltage level at the output of the amplifier. A higher power amplifier does not "drive" more "power" into the speaker at a given listening level. It is simply capable of delivering more power when it is demanded - increasing volume to increase the listening level, or to handle dynamic peaks.

Incorrect. Impedance is extremely variable in an active speaker. Basically, it's all over the place depending on the source material. A speaker's impedance rating is more of a prediction or an average.
 
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