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What power?

post #1 of 9
12/12/12 at 8:19am
Thread Starter 
I get the power ratings now days on recievers and AVRs being very optomistic sometimes but, I am currious about two older recievers I have. The first is a 1984 vintage Akai unit that I know puts out 40 wpc. On the back panel, it states total wattage usage as 120. The second is a slightly newer Pioneer unit that I think was rated at 50 wpc and the wattage usage is 190! So, where does the extra 40 and 90 watts respectively go in these units? Thats a lot! Or were these under rated?
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post #2 of 9
12/12/12 at 10:47am
The difference is dissipated as heat. But amplifiers and receivers don't draw the full power from the AC outlet all the time.

--Ethan
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post #3 of 9
12/12/12 at 12:54pm
Different companies use sufficiently different designs for their receivers that it's difficult to guess where the additional power is being used. The additional power might be available to the speakers, or it might be dissipated in the receiver's other circuits.
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post #4 of 9
12/12/12 at 1:00pm
Thread Starter 
I can understand maybe 10-20 watts but up to 90 (or more!) seems a lot to me.
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post #5 of 9
12/12/12 at 1:41pm
You need to look at the details of how they quote the amplifier power. Too often older receivers were rated with their "dynamic" power (thus needing only a small power supply) and not continuous, full bandwidth, all channels driven simultaneously (thus needing a much more robust power supply).
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post #6 of 9
12/12/12 at 2:23pm
Quote:
I can understand maybe 10-20 watts but up to 90 (or more!) seems a lot to me.
Just because an amp is rated at 100 wpc does not mean it cannot deliver more than that.The "official" power rating is a convention meant to allow apples to apples comparison of amps on some measure. A full power spec has several conditions attached to it, including bandwidth and distortion, not to mention the continuous power requirement. Relax any of those conditions, and the amp may well deliver more than the advertised power.
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post #7 of 9
12/12/12 at 4:14pm
As I understand it, you could take the same amp and swing the power requirement at least that far just by changing the bias to the out[ut transistors. Heat em up deeper into the class A end of AB and you use more power, and get less clean headroom as an added "bonus." (this from a guy who prefers his guitar amp's tubes biased moderately hottish 'cause it sounds so good when you turn up stupid loud).
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post #8 of 9
12/13/12 at 5:55am
If you want good estimation of how much power you can get from a receiver taketotal power consumption value (which has to be correctly stated by law), multiply by 0.6 (which is average efficiency of conventional AB class amplifier) and divide to number of channels. Independently published measurment results are usually close to the resulting value.
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post #9 of 9
12/13/12 at 9:17am
Thread Starter 
Quote:
Originally Posted by ap1 View Post

If you want good estimation of how much power you can get from a receiver taketotal power consumption value (which has to be correctly stated by law), multiply by 0.6 (which is average efficiency of conventional AB class amplifier) and divide to number of channels. Independently published measurment results are usually close to the resulting value.

Using this formula, that puts the Akai at 36 wpc and the Pioneer at 57 wpc. Which is kind of close to their published ratings.
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