Hi, first post in YONKS

Disclaimer: The figures here may not be exactly correct, I am interested in the workings outings, the numbers are quite arbituary. So, I have 2 amplifiers in my lounge, a Sony STR-D515 and a Yamaha RX-V795 (oh boy does this one sound good). I also have 2 sets of speakers, some 80W Mach Monitor Speakers (8 ohms) and some 8 ohm 100W Kef's (oh boy do these sound good )

Prior to yesterday, I ran all 4 speakers from the Yamaha amplifier. Trouble is, having no neighbours, and liking Electronic Dance Music, I tend to hoon it out at high volume, and this would sometimes mean the Yamaha would click its relay and go into protect mode. No probs, turn it down a bit and turn it back on...

Now, I have the Sony running the Mach's, and the Yamaha running the Kef's (oh boy does my lounge sound good). Question is, how much extra power would this be using, at (roughly) the same perceivable volume, if any?

The Sony is rated at 70w+70w into the main speakers, and the Yamaha I think 85w+85w. The Yamaha says it will draw ~350w on the back. The Sony doesn't say anything.

What was happening before? Was I drawing 170W (we'll pretend it was running at full twat)?
Am I now drawing 310W with it running full twat?
How do you calculate these things? For ref, I never used - or use - the 'surround' / 'centre' / 'sub' part of the amplifier, just the 2 sets of stereo 'Main' speakers.

Cheers guys

Try a Kill-A-Watt?

Probably not.



Mostly we don't. Maybe someone measures it. Hence the Kill-a-watt suggestion in the other post.



What is your real question?

Just idle curiosity?

Afraid of hurting something?

I guess the real calculation is what is the ratio between electric wattage and rms wattage?

And yes, just curiosity, no fear.

*In addition to that, amplifiers are using different methods for amplifying and also have different ways of drawing power. Class B amplifiers only draw the power that it's really using, but it's not of great quality. Class A amplifiers draw the same wattage no matter how loud you play, and it's of a better quality than Class B. Then theres some other implementations that combine these or use different methods to preserve quality and efficiency, but I couldn't really find any useful information on these, probably because most methods are proprietary.

This is why I suggest you use a Kill-A-Watt instead of guessing. Personally I don't know the Kill-A-Watt since we don't use this in my country, but cheap wattage measure devices sometimes report incorrect usage, so make sure you measure using a proper device. In my country they can be lended from energysuppliers and librarys.

(*This is what I myself measured using a cheap device, since I have not yet tried the proper Kill-A-Watt. I think I googled some evidence that this was normal behavior of some amplifiers. I will measure this properly and reply in the thread about my findings)

Wikipedia

Actually, probably most implementations are AB, combining high quality of A at low volumes and relative energy efficiency of B at high volumes.

Not sure, but I think it's difficult to speculate at one remove, although it is measurable. If one amplifier were an audiophile-approved but painfully inefficient Class A design, it's spending more of its energy budget acting as a heating unit than a sound-maker. OTOH, a Class D design is unbelievably efficient by comparison and will be far less power-mad on a watt-for-watt power output basis.

That assumes all other things are equal. Logic control, scrolling displays, LEDs everywhere and more may account for a small, but significant, changed in the demands by the amplifier. Were you to compare two products poles apart in design terms, one could be many times more efficient at transferring electrical power into amplifier power than the other.

In other words, ratio... what ratio?

It's not that simple. As others have pointed out, receivers draw a fair amount of current just sitting there, running the signal processing and idling the output stages.

When you turn up the volume, the impedance curves of the loudspeakers and the dynamics of the music come into play.



For the ca. $25 price, the Kill-A-watt would be a good tool for satisfying some of your curiosity. There are now both 120 volt and 240 volt versions.

Well if both amplifiers are of class AB design (typical) and both running on similar internal rail voltages and if your previous arrangement was both speakers in parallel then there's actually a good theoretical case that the total power consumption of the two amplifiers combined will be similar to that of the previous single amplifier. As others have pointed out there's a lot of if's involved here. Also note that I am referring to the case where you are listening at your typical (apparently loud) levels, obviously ay very low load or no load you'll have more "standby" power consumption with the two amplifier set up.

Thanks very much for all the replies peeps, gave me some interesting reading to do. The Kill-A-Watt sounds like an ideal investment

I just measured my H/K AVR130.

Rated: 2x55W (5x45W in multichannel mode)

In idle and with normal volume, it measured roughly 50W. If I turned it somewhat loader it reached 65W, but I was a little hesitant, as I have neighbors I think it would reach about 80W if I really crank it up to it's max and don't use ReplayGain.

Weird thing is, according to the specs: 68W idle, 540W maximum (2 channels driven)

Also I couldn't find which kind of Class it's using.

Not weird. The 540 maximum is based on a sine wave test of all channels.

Music always has about 10 times or less (IOW even less power than 1/10) power than the comparable sine wave.

Just guessing, but lest say that your power amp is 50% efficient for any power it puts out over some very minimal (less than 1 watt) power level. You found 15 watt additional power draw, which relates to 8 watts actual power delivered to the load, which could have a peak value of 80 watts (40 wpc) or more. You may have already pushed your amp into clipping.



I'd put money on Class AB.