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What Is The Difference in a Watt in One Receiver vs. Another?

AVSJeff

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This question was asked on one of the other Forums I follow:

Why is it nearly pointless to compare amplifiers using their sustained power rating (watts) and how to explain this to the 'Average Joe'?

Here are my comments:
Probably the easiest way for the Average Joe 'Spec Sheet Reader' to determine what makes one amplifier better than another when rated at the same sustained output wattage rating is as follows:
1) How much does the amp weigh? Good amplifiers (and AVR's) have a lot of weight to them because of the components used in the power section (power supply, transformers, capacitors, etc). If you pick up an AVR and it has the weight of a card-board box, it's performance is probably the same (lousy).

2) Look at the rated power output at different impedances (forget how efficient your speakers are and what their impedance is rated at). Most amplifiers are rated at 8 ohms, but more importantly, can it drive a 4-ohm load? A 2-ohm load? and what are the power output ratings at these impedances? A long time ago I owned a Luxman R-117 AV receiver rated at 170 wpc at 8-ohms but was rated at 720 wpc at 2-ohms. That receiver weighed a ton! This receiver was also only one of a few that could drive Infinity RSiiB speakers that had a nominal woofer impedance of 1/2 ohm. I did a lot of amplifier testing using these speakers because they could shut-down all but the best of amplifiers.

3) Look at the Damping Factor. This will tell you how much power the amp has 'in reserve' to reject the power coming back to the amp from the woofers in the speakers moving. This is a good indicator of how much capacitance the amp has. The more the better.
Bottom line for Average Joe to understand watts and how they perform is to look at these basic things. Of course, component and build quality will also have an effect but not as substantially as these.

Am I missing anything here?
Jeff Ripplinger
AV Science Sales
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Re: What Is The Difference in a Watt in One Receiver vs. Another?
« Reply #1 on: June 15, 2022, 04:01:31 PM »
1) Seems more applicable to classic A/B amps but now with many high quality D amps available it's not comparing apples & oranges. But maybe in the same amp class, it is ok. 

The other 2 seem pretty strong.

The power supply capacity could be an indicator too if that is known.

bmoney

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Re: What Is The Difference in a Watt in One Receiver vs. Another?
« Reply #2 on: June 15, 2022, 04:54:38 PM »
also rated power to each channel vs all channels

Many times they boast high watts but it’s to one channel driven which quickly diminishes as soon as you start going multi channel
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Re: What Is The Difference in a Watt in One Receiver vs. Another?
« Reply #3 on: June 15, 2022, 06:12:11 PM »
also rated power to each channel vs all channels

Many times they boast high watts but it’s to one channel driven which quickly diminishes as soon as you start going multi channel
Beat me to it...I was going to say the exact same thing. 
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