are these ratings consistent -- over the years ?

the back plate on my 10 year old panny egg says 57 watts -- it got LOTS of power --

if a 25 year old traditional box also said 57 watts -- would it have the same output ?

thanks

people often use the power rating on the back. It has NOTHING to do with the AUDIO power output. It is the total power consumption if everything is turned on, at 3/4 volume. The "typical" IC's are between 5-15 watts PEAK. And think about it, if it runs on D cells, it won't last very long!

Just thought I'd pass it along.

Very few boxes list output power ratings on the back panel although some do.
If it gives a number followed by "x2" or "output" safe to assume is output wattage.
if it only says "45 watts" chances are that is power consumption.

ok - thanks kitt and TA

Both 57W boxes would have similar ouput power in watts since the amp section spend the major amount of watts.
Sound presure level perhaps is different, and it depends of the speaker system design.
The same power would appear like a lot or a little to the human hear depending of the speaker sensibility.
Old tube amps, with only 4.5W reach higher presure levels using high sensibilitry speakers with 12 inch paper cones that are ligthweigth.
Listeing they, and comparing they against a 15W BBX perhaps you would feel the same amount of energy, because the different speaker performance, that waste in the BBX and save in the tube amp.

Another example was the RS4300. Before reading a brochure I was sure that the unit was somewhere betwen 5 and 8 watt per channel.
The brochure says 2.2W+2.2W !!!!. Sound as louder as other 6W+6W Panasonic I have !!!!!!
Speaker and cabinet design perhaps makes the difference.

RBJ, that is the maximum power in watts that the radio is capable of drawing at any one moment. It has no relevance to the actual amp IC capabilities.

The IC amp is the section wich takes more watts (power) from the supply of the BBX.
A tipical BBX has 3 ohms speakers. So driving both channels would eat as much power as HDC*HDC/3
Where HDC is the half of the voltage when you operate with batteries. So if DC is 12V, the the amp chip eats 12W. For 15V eats 18W.
That is both channels driven at the maximun rated power and signal a sine wave.

No other section in the BBX takes this amount of power form the tranformer.

You can notice in a BBX with light, or VUMETER in batt position, that only when volume is loud, the power goes down (the light decrease its brigth folling the music) ... that because the AMP is selfish ...

Motor, turner, preamp, would add 2 more watts to the final BBX consuption.

quote:

Originally posted by SUCCESS:
The IC amp is the section wich takes more watts (power) from the supply of the BBX.
A tipical BBX has 3 ohms speakers. So driving both channels would eat as much power as HDC*HDC/3
Where HDC is the half of the voltage when you operate with batteries. So if DC is 12V, the the amp chip eats 12W. For 15V eats 18W.
That is both channels driven at the maximun rated power and signal a sine wave.

No other section in the BBX takes this amount of power form the tranformer.

You can notice in a BBX with light, or VUMETER in batt position, that only when volume is loud, the power goes down (the light decrease its brigth folling the music) ... that because the AMP is selfish ...

Motor, turner, preamp, would add 2 more watts to the final BBX consuption.

While your statements are valid on its face, you've missed a critical piece of the equation and you are assuming that every device is 100% efficient. Those class A/B amps are barely 45% efficient from that time frame considering that and ideal class A/B design mostly approaches 79% under perfect conditions.

When you factor that some amps could be class A, now efficiency is around 30%. You can not correlate amp power consumption via ohms law as a direct translation. These electronics from this era do not operate as efficient device, most of the output power is dissipated as heat.

Just some food for thought.

Ok, I didn't want to be boring ... of course no amp is 100% eficient. Worse then, I need more watts from the supply to reach 12 W RMS.

They key fact is the large amount of watts are spent by the AMP section. So, at same power consuption from the mains, similar power output is expected (electrycally). Then speaker efficiency plays a lot. Same output power don't shields the same SPL ...

And finally I assumed that the egg and the brick have similar IC's, so similar efficiency (or wasted power in the other hand) is expected too.

Ic's launched lots of years are still in production ... and cheaper as the times passes, are likely to be used in mass consumer electronics rather the new ones.