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  1. #1
    Senior Member 3dbinCanada's Avatar
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    Interesting link on the FTC and amplifier power ratings

    Main/2nd/3rd System
    AVR Yamaha RX-V1800/RX-V1900/RX-V1500
    Turntable ProJect Xpression III with Ortofon Red
    Cassette Deck Yamaha KX-800U/
    KX-800U/KX-630
    BluRay Yamaha BD-S681/Sony UBP-X800
    Media Player Iomega + 1TB internal drive/WD TV Live Plus + 3TB USB drive
    Display Samsung UN65KU6491 65"/UN55MU7000 55"
    Speakers Front:PSB Image T-45/400/Alphas,Center:PSB Image 8C/100C,Surrounds:PSB Image 1B/RBH A600
    Subwoofer Rythmic LV12-R/PSB Subsonic 5/Energy XL-S8

  2. #2
    Administrator Tracy Rainwater's Avatar
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    I and others on this forum have been advising people who are looking into buying a new AVR, or amp vs AVR, to take a close look at how the manufacturers are rating wattage.

    It is very common to see ratings with only two channels driven, yet it's not a stereo power amp.......it's a multi-channel home theater receiver. I absolutely hate it when I see AVRs with these types of ratings.

    Luckily there are some manufacturers who offer wattage ratings with all channels driven simultaneously. Those are the companies that I will continue to recommend.

  3. #3
    Senior Member 3dbinCanada's Avatar
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    Quote Originally Posted by Tracy Rainwater View Post
    I and others on this forum have been advising people who are looking into buying a new AVR, or amp vs AVR, to take a close look at how the manufacturers are rating wattage.

    It is very common to see ratings with only two channels driven, yet it's not a stereo power amp.......it's a multi-channel home theater receiver. I absolutely hate it when I see AVRs with these types of ratings.

    Luckily there are some manufacturers who offer wattage ratings with all channels driven simultaneously. Those are the companies that I will continue to recommend.
    The problem I see with ACD (all channels driven) is that it very seldom is a rare event that all channels output the same information at the same level at the same volume at the same time. In my opinion, ACD tests the sensitivity of the AVR's protection circuitry and how conservative the manufacturer is. Yamaha 2 channel tests slay most other manufacturers 2 channel test yet show the poorest in ACD. How is that possible when the same power supply is used in both? The only answer I can come up with is the sensitivity of the AVR's protection circuitry and when its designed to engage.
    Main/2nd/3rd System
    AVR Yamaha RX-V1800/RX-V1900/RX-V1500
    Turntable ProJect Xpression III with Ortofon Red
    Cassette Deck Yamaha KX-800U/
    KX-800U/KX-630
    BluRay Yamaha BD-S681/Sony UBP-X800
    Media Player Iomega + 1TB internal drive/WD TV Live Plus + 3TB USB drive
    Display Samsung UN65KU6491 65"/UN55MU7000 55"
    Speakers Front:PSB Image T-45/400/Alphas,Center:PSB Image 8C/100C,Surrounds:PSB Image 1B/RBH A600
    Subwoofer Rythmic LV12-R/PSB Subsonic 5/Energy XL-S8

  4. #4
    Administrator Tracy Rainwater's Avatar
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    I am no engineer but here are some basics that I think are accurate.

    When comparing an AVR's amp section to a dedicated power amp, there are a few things to consider but the biggies are the power supply and output transistors.

    An AVR has to do many things.
    Power 5 -12 Channels
    HDMI Switching
    Audio Signal Processing
    Video Signal Processing
    Auto Setup
    Maybe even an AM/FM/Satellite Radio Tuner

    All this takes up space inside the box so space for large components such as power transformers, audio and power capacitors, and heatsinks, are at a premium. So, the engineers have to scale a good many things down. The smaller transformer can't produce as much power as a larger one and some of that power has to be used to take care of all the other functions of the AVR as well.

    In the end, there is less available power (voltage) to run solid power to all 5-12 channels at the same time, in many cases.

    Add to this, the output sections of each channel are also scaled down. Even if the power supply had more voltage to offer each channel, if the output section particularly the output transistors may not be able to effectively use that power to create more wattage.

    Now, do you need equal power to all channels? Yes and no and it really depends.

    The largest considerations to me would be room size, speaker efficiency, and if you are running them full range or not. Add to that, I can think of some action films that have a pretty demanding soundtrack for all the speakers, not just the LCR channels.

  5. #5
    Senior Member 3dbinCanada's Avatar
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    I would have to agree with you generally but I still think the ACD test on the upper tier AVR is more dependent on the conservativeness of the protection circuit than anything else. However, the same power supply is being used for both ACD and 2 channel tests. If an AVR excels ( goes far beyond rated output) in the 2 channel test, but doesn't do well in ACD tests, then the only thing that I can think off is that the protection circuit used to limit power is a bit too reactive which is determined by the manufacturer.


    As an example, read through the power analysis done by Audioholics on the old RX-A3000.. It outpowered an Emotiva power amp on 2 channels driven test but the RX-A3000 didnt score well in the ACD test. This fact was mentioned in the review and the reasons reflect my thinking in this case.

    https://www.audioholics.com/av-recei...0-measurements

    Main/2nd/3rd System
    AVR Yamaha RX-V1800/RX-V1900/RX-V1500
    Turntable ProJect Xpression III with Ortofon Red
    Cassette Deck Yamaha KX-800U/
    KX-800U/KX-630
    BluRay Yamaha BD-S681/Sony UBP-X800
    Media Player Iomega + 1TB internal drive/WD TV Live Plus + 3TB USB drive
    Display Samsung UN65KU6491 65"/UN55MU7000 55"
    Speakers Front:PSB Image T-45/400/Alphas,Center:PSB Image 8C/100C,Surrounds:PSB Image 1B/RBH A600
    Subwoofer Rythmic LV12-R/PSB Subsonic 5/Energy XL-S8

  6. #6
    Administrator Tracy Rainwater's Avatar
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    The protect circuit may be part of the equation. I tend to look at power ratings and the reasons why AVRs generally don't fare as well in the ACD tests and relate it to the water in your house.


    Think of the AVR's power supply was your main water supply and all those individual channels (5-11 or more) as faucets. With residential plumbing, what usually happens is that your main water supply is delivered to your home in a larger diameter pipe than what runs to each individual faucet. So, you have this larger pipe (AVR's power supply) running in different directions in smaller pipes to all sorts of things in your home (the AVR's individual speaker channels).

    I'm not going to relate this to water pressure but to flow. If you deliver the water (voltage) via smaller pipes (output transistors etc.) you are going to have less flow (wattage with multiple output devices active). You may have a decent wattage rating into 2 channels even though it has those smaller output stages because the transformer doesn't have to work as hard and all its power is directed to those 2 channels. If you run the total power from that power supply into 5-11 or more channels at the same time, the output stages of each channel severely restrict the power, build up heat, and cause distortion because the power supply cannot push the power out through all those channels at the same time without compromise.

    Heck, maybe we're both right, each having 1/2 of the equation. Maybe the designers of these AVRs know the limitations (which I'm sure they do) and build the protection circuit around the system's inadequacies.

    "We'll just shut her down with the protect circuit before she goes into thermal nuclear meltdown".

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