Power consumption v/s output power

Hi friends,
When we come across specs. of amps and av receivers of different brands, it is noticed that many of them shows same output (min rms power) but consumes different electric power. Is there any thumb rule for the min. rms can be obtained for a particular input power (wattage)
For example Yamaha RX-V 661 outputs 90 watts into 7 channels while it consume 380 watt electric power.
But Harman Kardon AVR354 take an input of 890 watts to output 75 watts into 7 channels.
(both drives all channels at 20Hz – 20kHz into 8 ohms)

What will be the reason for this much difference in power consumption?

Ajith lal

Ajith,
I'm confused by your specs on the Yamaha. If it consumes 380 w, I don't know how it can output 630 w (7x90w). Are you sure about the numbers?

Here it goes:
GENERAL
• Power Supply
[U.S.A. and Canada models] ............................. AC 120 V, 60 Hz
[General model]
....................................... AC 110/120/220/230–240 V, 50/60 Hz
[Asia model]
.................................................. ... AC 220/230–240 V, 50/60 Hz
[China model] .................................................. .. AC 220 V, 50 Hz
[Korea model] .................................................. .. AC 220 V, 60 Hz
[Australia model] ............................................... AC 240 V, 50 Hz
[U.K. and Europe models] ................................. AC 230 V, 50 Hz
• Power Consumption
[U.S.A. and Canada models] ................................. 380 W/480 VA
[Other models] .................................................. .................. 390 W
• Standby Power Consumption ....................................... 0.1 W or less
• Maximum Power Consumption [General model only]
6ch, 10% THD .................................................. .................. 800 W
• AC Outlets
[U.S.A., Canada, and China models]
.................................................. ........ 2 (Total 100 W maximum)
[Asia, General and Europe models] ...... 2 (Total 50 W maximum)
[Australia and U.K. models] ............... 1 (Total 100 W maximum)
• Dimensions (W x H x D) ................................ 435 x 171 x 393 mm
(17-1/8 x 6-3/4 x 15-1/2 in)
• Weight .................................................. ............ 11.6 kg (25 lbs 9 oz)
* Specifications are subject to change without notice

Dear Mr.Ajith

The reason why HK has less watt is they normally rate their power in ampere , I think AVR 354 is 75watts @ 25 ampere . When i went to the JBL showroom in Mumbai , i can see that when the volume is just above minimum , i can hear the sounds from all the speakers and the clarity is much more then the yamaha or marantz or denon . For the last few days i have been auditioning many system in lot places in mumbai and Pune.
As far as the AVR is concern i will suggest HK to any one any day, Just audition them .

vijay.

Vijay,
I'm not intended to buy HK AVR.
But Power should be absolute whether in terms of ampere or voltage.
I'm talking about ratio of out put power to the input.
Nobody commenting on that.
This is just not the case with HK and yamaha.
I know HK stating output power in true way.
Ajithlal

Here the specs of HK354:Power Requirement : AC 120V/60Hz
Power Consumption : 118W idle, 890W maximum (7 channels driven)Front L & R Channels : 75 Watts per channel @ <0.07% THD, 20Hz – 20kHz into 8 ohms
Center Channel : 75 Watts @ <0.07% THD, 20Hz – 20kHz into 8 ohms
Surround Channels (L & R Side, L & R Back) : 75 Watts per channel @ <0.07% THD, 20Hz – 20kHz into 8 ohmsHigh Instantaneous Current Capability (HCC) : ±35 Amps

From faqs of HK site:

A Harman Kardon 50-watt amplifier will sound better, louder and cleaner than most 100-watt amplifiers from other companies. The reason is very simple. We give "true" wattage ratings, and our amplifiers utilize something called High-Current Capability (HCC). Please see the comparison below for further explanation. Other companies (100 watts):
Many companies have found new, convenient ways to get "big" wattage ratings on their amplifiers. They may take one frequency or tone (1kHz) and push it through one channel of amplification. This way the power supply only needs to supply power to one tone and one channel (no one listens to one tone through one speaker). This is not a difficult task for a power supply, so you get a nice, high rating like 100 watts. Now let's feed that one tone (1kHz) into 2 channels. Now the power supply has to supply power to 2 channels. The wattage rating is drastically reduced. Now let's take that one tone and make it ALL tones (pink noise). The power supply now has to supply power to all frequencies in both channels. Again, the wattage rating is drastically reduced. Now, your 100-watt amp is suddenly 50 watts (approximately).

Let's take it one step further. When you turn the amp up and begin to average the 50 watts of power, what happens to all of the dynamics/peaks in the sound? It can't get any louder, because the amp has hit its "ceiling," so the sound gets "clipped." The human ear typically can?t hear this clipping because peaks pass by so quickly but, nonetheless, the dynamics are gone.

Our amplifiers (50 watts):

We still rate our amplifiers the old-fashioned way - all frequencies with both channels driven. So "50 watts" is 50 watts. Twenty-five years ago, a 50-watt amp was very powerful. These days you can go to a store and hear a "300 watt" receiver and it won't impress; it lacks dynamic punch.

Now let's take it that extra step. When you turn the amp up and begin to average the 50 watts of power, the amp still needs to put out much more power every time a snare drum, triangle, or movie dynamic (e.g., hand slapping a face) hits. Our amps are able to instantaneously put out 20-100 amps (depending on the model) of high current to the speakers, allowing those dynamics to come through loud and clear, without any distortion. This brings the overall decibel average up, making it seem even louder that 50-watts.

yes ajithlal
even marantz sr 7002 consum 780 w but even pioneer vsx 1018 and pioneer LX71 consume only 380w power ,HK,MARANTZ,consume more power

I was harmon kardon owner 4 years back and take my word - irrespctive of claimed lower wattege so sound blooooooooodyyyyy powerfullll!!!

Also beleive on your ears only - infact If you have elders or toddlers at home I will advise you against buying too powerful system!!

Hemant

Let me try to throw some light:

In most home theater receivers, the manufacturer assumes that not all the channels would be active at any given point in time. A good manufacturer often considers the Left, Right & Center, plus an active sub. Hence an amp may be rated to consume 670Watts while at max. volume it would output 330 watts, through either or all the channels.

Which is why many manufacturers of receivers quote the output with only L & R channels, and not with all channels.

But some manufacturers only consider the left and right to be active, which is the case of the yamaha receivers.

According to them when you are playing a DVD, its quite likely that the sound track never demands all the channel to be active.

Hence we may say that they're over subscribing. That is a way to economize the cost of manufacturing.


Finally, when it comes to sound quality, there are other factors such as filters employes, which often provide additional boost to the lows and highs, which often makes consumers fall for these products. however, do remember that these may sometimes be at the expense of distortion.

when purchasing, one should be sure of the total power output at 0.1% THD with atleast the sum of the power output of L, R & C should be 50% or less than the power input. Such an amp is said to be decent enough.

Ofcourse if the sum of power output of all channels is about 50% of the total power input at 0.1THD, then that's the best receiver to go for, however, so far, I've only seen such amps with stereo receivers.

In the above comparisons I'm assuming a continous power output from 20Hz-20000Hz frequency range at full power.