confusing watts

[jayantadak]

Hi,

In my Denon AVR-1604 manual guide the Power amplifier rating output stated is as under:

Front: 75 W + 75 W (8#/ohms, 20 Hz - 20 Khz with 0.08% THD)
130 W + 130 W (6#/ohms, EIAJ)

Centre 75 W (8#/ohms, 20 Hz-20 Khz with 0.08%THD
130 W (6#/ohms, EIAJ)

Surround: --- same as FRONTS --

I fail to understand what is the exact wattage of my AVR. Ideally speaking it is said as 75 W x 5 . Then what is '130 W' which is specified in the second line. Would our HFV members let me know ?

P.S. I wasn't having the proper symbol font on my key-board hence used the '#' symbol.

Regards,

JAYANT ADAK

 

[venkatcr]

Sound is sent as an electrical current by the amplifier to the speaker. The speaker, in turn, has resistance to the current measured as 'x' ohms. Most speakers have 4, 6 or 8 ohms. The higher the resistance, for the same energy sent by the amplifier, the speaker will deliver a lesser amplitude of sound. The amplitude is measured as Watt.

Thus the same amplifier can drive a speaker with 6 ohms resistance to 130 watts, and a speaker with 8 ohms resistance to 75 watts. In both cases, this is the maximum capacity of the amplifier, which hopefully you will never get to use.

Cheers

 

[navin advani]

EIAJ refers to Electronic Industries Association of Japan.

When manufacturers publish specifications they are expected to do so as per a set of standards (DIN, EIAJ, CEA, FTC etc..). A common standard is RMS (aka Root Mean Square) which is derived from the average power of a sinusoid.

Some standards are more stringent like FTC's standard which says something similar to this "A manufacturers stated power rating in RMS must be met, with ALL channels driven, into a given load, over the advertised frequency range usually 20 Hz to 20 kHz at no more than the rated total harmonic distortion (or THD)"

So you would get a manufacturer stating that their amplifier can produce "100W RMS both channels driven into 8 ohms (nominal), 20Hz TO 20Khz at THD < 0.01%"

THD numbers are frequency dependant and most transistors produce more THD at frequency exttremes (20Hz and 20kHz) than at 1kHz.

EIAJ standards are far more leinient something like "single channel driven at 6 ohms at 1 kHz with 1% THD clipping".

Hence a STEREO amplifier that produces 100W RMS (both channels) at 8 ohms at 20-20kHz at 0.1% THD (aka FTC) will produce about 200W at 6 ohms (single channel) at 1kHz at 1% THD.

EIAJ is sorta like a halfway house between FTC standards and the famous "PMPO" ratings. DIN, CEA, etc.. are other standads. Google can tell you more than I can.

 

[fusseltier]

Rms is not the average power of a sine wave, it is the root mean square of the peak of a sine wave, which is 0.707 x peak.
(peak is half of the sine wave)

Average power is 0.637 x peak.

There is a difference.

PMPO is an imaginary term used for marketing to confuse people and make them think they are getting a powerful amplifier.
Peak Mean or peak Music Power Out
Is only one specific frequency at one specific instance in time.
There are no conversion formulas for PMPO.
I usually divide PMPO by 85 for rms, but it could be 150 since it's only an exaggeration of power to sell something.

Just realize, if ot says 22,000 watts PMPO, a 220vac 60 amp service to a house only provides 13.2kw, so you'll blow the breaker if you played it loud.
Plus, the stereo is made of plastic and so are the speakers, so it would need serious cooling or it would melt.