RMS Wattage Vs Power Consumption

Law of conservation of energy is at times broken by some manufacturers of Hifi amps :). The power rating of your 6 ch amp may not be the continous output of all the 6 channels driven simultaneously, induvidually they may be capable of delivering 100W RMS. A class AB amp which most of the AV amps are can easily achieve an overall efficiency of 50% which in turn can lead to a maximum power consumption of 400W for producing 100rms * 2 for a stereo application.

International Hi Fidelity (IHF) had specified certain norms for the manufacturers in publishing the out put of amplifiers. Dynamic Power as per IHF spec is the power that an amp can produce for 20ms into specified load impedences (8,6,4,2 ohms) This data is used to figure out how well the amp performs into different frequency driven impedence variations of most loudspeakers.

Higher power output need not give you higher decibel(sound pressure) it again depends on efficiency of speakers and room acoustics.

Hi! Koka,
U have answered ur question by urself. Exactly how can the amp deliver 6 x 100 when the power con is only 400W. THis is because when they say 6 x 100, they actually mean that one channel driven will give u 100, so you must assume that it will give 6 x 100! but it will be about 65w RMS all channels driven. Gimmicks buddy .

Now look at an hi-end amp like a ARAGON 8008 which is a 200w rms/channel stereo amp. Do you know that the power con is 1500w. Now thats reality.

Only very few mid-end amps give u pwr figures for all channels driven.

Rgds

Prithvi

So, it does not mean 100 watts output per channel simultaneously. All it means is each of the channels can output 100 watts not necessarily at the same time. In case of my Yamaha receiver at 100% efficiency the most it will output is 400 Watts. In practice, it is probably 320 Watts at 80% efficiency. Am I right?

My other question is:
If my receiver needs 400 watts of power at the volume knob turned all the way up to max will it consume 200 watts if the volume knob is turned only half way up? The reason I am asking this question is by doubling the input wattage one would have a 3dB increase in SPL. If I am listening at say 74dB I would like to know roughly how much electricity the receiver is consuming.

To put the question in other words, will it always consume 400 watts of power. If the volume knob is only half way down, then the rest of the input power is wasted! I guess it will consume proportionately.

HI Koka,

The 400w is the nominal power requirment of the amp, it is like say a 1200w Iron box, the iron box may draw a maximum power of 1200W while its thermostat is on, same is the case with your airconditioners, the pwer req may be stated as 3000w but the equip may draw lesser.

The position of the volume control need not be true indication of the power o/p produced by the amp, o/p depends on the drive signal voltage and type of signal. Sound pressure also varies , for eg. if you supply white noise (a signal consisting of complete freq starting from 20hz - 20khz) the sound level produced by the amp at the same volume position will be different from that of a single freq of say 3khz.