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Topic: Power Consumption of Hifi Amplifiers (Read 10748 times) previous topic - next topic
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Power Consumption of Hifi Amplifiers

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

Power Consumption of Hifi Amplifiers

Reply #1 –
Try a Kill-A-Watt?
Can't wait for a HD-AAC encoder :P

Power Consumption of Hifi Amplifiers

Reply #2 –
Quote from: Lev on
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?


Probably not.

Quote
How do you calculate these things?


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

Quote
For ref, I never used - or use - the 'surround' / 'centre' / 'sub' part of the amplifier, just the 2 sets of stereo 'Main' speakers.


What is your real question?

Just idle curiosity?

Afraid of hurting something?

Power Consumption of Hifi Amplifiers

Reply #3 –
I guess the real calculation is what is the ratio between electric wattage and rms wattage?

And yes, just curiosity, no fear.

Power Consumption of Hifi Amplifiers

Reply #4 –
*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
Can't wait for a HD-AAC encoder :P

Power Consumption of Hifi Amplifiers

Reply #5 –
Quote from: odyssey on
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.

Actually, probably most implementations are AB, combining high quality of A at low volumes and relative energy efficiency of B at high volumes.
Ceterum censeo, there should be an "%is_stop_after_current%".

Power Consumption of Hifi Amplifiers

Reply #6 –
Quote from: Lev on
I guess the real calculation is what is the ratio between electric wattage and rms wattage?

And yes, just curiosity, no fear.


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?

Power Consumption of Hifi Amplifiers

Reply #7 –
Quote from: Lev on
I guess the real calculation is what is the ratio between electric wattage and rms wattage?


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.

Quote
And yes, just curiosity, no fear.


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.

Power Consumption of Hifi Amplifiers

Reply #8 –
Quote
Question is, how much extra power would this be using, at (roughly) the same perceivable volume, if any?


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.

Power Consumption of Hifi Amplifiers

Reply #9 –
Thanks very much for all the replies peeps, gave me some interesting reading to do.  The Kill-A-Watt sounds like an ideal investment

Power Consumption of Hifi Amplifiers

Reply #10 –
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.
Can't wait for a HD-AAC encoder :P

Power Consumption of Hifi Amplifiers

Reply #11 –
Quote from: odyssey on
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)


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.

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


I'd put money on Class AB.

Power Consumption of Hifi Amplifiers

Reply #12 –
Neat topic.  Here I was surfing the 'net, and came across this.

Ballparking power consumption is not so hard of a thing to do.

Power (watts) = Volts * Amps

Measuring power consumption with a meter won't show you the real peaks - they're too fast.  I saw some interesting readings for average or nominal power consumption (by Odyssey).  (~65 watts when loud - that makes sense).  That's also really loud.   

You need to know the 1 watt rating for your speakers to do this.

Example: speakers: 90 dB/1 watt, 8 ohms

Each increase by 3 dB requires twice the wattage to drive.  At 1 watt per channel, each example speaker produces 90 dB SPL.  At that level, each additional speaker adds 3 dB, and so with two 90 dB speakers playing at 1 watt, that's 93 dB in the room.  With four speakers, it would be 99 dB at 1 wpc.  Also, this is measured at a distance of 1 meter.

At 1 wpc, there is 93 dB with two speakers.  At 2 wpc, its 96 dB.  At 4 wpc, its 99 dB.  At 8 wpc, its 102, and at 16 wpc, its 105.  At 32 wpc, its 108, and at 64 wpc, its 111, which should contribute to lifelong hearing loss in short order. 

Dynamic headroom represents 10 dB over the average output as a rule of thumb.  Its ballparky, and speakers can change the rules a bit, and so can how far we've traveled from where we started (the numbers skew).  Electronically, the dynamics are why this application is such a bitch for amplifiers.  On the one hand, we may have an average power consumption of 50 wpc (when VERY loud and in the process of blowing the speakers).  On the other hand, a 10 dB headroom means 500 wpc peaks.  After the 10 dB, I add 3 dB as a "crest factor", which means multiplying the average consumption by 20 (instead of 10) to get the peak wattage, which in this case would be 1000 wpc.

Let's say that its the same speakers as above; 90 dB/1 watt, 8 ohms.  A very high voltage for a speaker might be around 40.  The voltage, which in this case would cycle from +40 to -40 and back again, is also the physical position of the driver.  Where 40 volts is the speaker max, At +40, the driver is fully extended forward, at 0 it is centered, and at -40 it is all the way recessed.  If you want to know how far your woofer is traveling, you can stand perpendicular to it, and this will give you a visual on its current range of linear travel.  Typically, you won't be able to see movement from straight on, as its moving way faster than your eye.  Once it reaches its max travel, it's done, and it won't produce any more output regardless of how much power you have.  After that, it goes into "compression".  Normally, there's 10 dB of headroom for peak transients, but not anymore.  If the driver is capable of 105 dB (as configured), and the average output is 105 dB, then the driver is fully compressed, because all of the peaks will be at 105 dB.  In fact, there's one or two dB added during the compression phase, since the average is more accumulated.  The dynamics will be gone.  The speaker will also most likely become tonally imbalanced, since woofers will most often go into compression long before the tweeters.

Something in this thread made me think of this...  There's always a lot of talk about how big and powerful an amplifier needs to be to be as big and powerful as we need them to be.  How big and powerful is that?  Well, in fact the average power consumption in the home is less than 1wpc, such as when playing at around 75 or 80 dB, which is quite a bit below 1 watt.  At 75 dB, even the peaks are at 85 dB, which is about 1/4 wpc on a 90 dB speaker PEAK!  Meanwhile, like so many, you want to drive your speakers to max, which can be done actually with a 30 watt amp (running at twice its rating), but can only be done cleanly with more power.  A 30 wpc amp will generally drive any speaker to its max, but more than that makes the sound more clear.  Actually, 60 wpc from a 30 wpc amp would most likely be at or near 100% THD.  I've heard it done.  I couldn't make out the song, or the vocals, or much beyond a beat, but I heard it. 

Dynamics internally to the electronics just have a way of messing with internal values, along with the clarity and quality of the sound, until they are properly dealt with.  Dynamics also turn audio into a much higher wattage affair.  And for what... A split second?  Jeesh.  EE's roll over in their grave when they first hear of the watts we like to play with.

Hope that helps.  A RatShack SPL meter might be fun to play with.

My speakers are rated at 87.5 dB/1 watt, 5 ohms.  Marantz btw is good for 4-8  ohms for sure, but at 4, its pushing it if you like it loud. I have a Marantz sr7002 that doesn't seem to fret about my 5 ohm speakers.  I know that they will max at 108 dB for the pair, at about 7 wpc nominal (average), 70 wpc peak, and 140 wpc with a little crest factor.  140 wpc into 5 ohms is the number I use for these speakers needs.  Meanwhile, every manufacturer makes their own ratings.  Caveat emptor on that one.  Check the power when tested in a review, and see if the manufacturer is full of it.  A fully qualified power rating must state: wattage, THD, driven or not, rms or peak, what frequency range, and into what load (ohms).  If it doesn't say all 6 things, then its missing something.  "RMS wattage" was created by MFRs in the 60s, there is no such thing as an RMS wattage.  RMS only applies to AC voltage, whereas RMS wattage is an MFR concoction that attempts to "RMS" the current as well, which I think is really flaky.

Cheers, and happy listening -
Mark

Power Consumption of Hifi Amplifiers

Reply #13 –
I think what was being asked back when this thread first appeared is a little more complex than you are painting it as.

If you measure power consumption at the speaker terminals, it doesn't factor how much power is lost through dissipated heat. That varies according to amplifier design. A Class D design is notionally at least 90% efficient, but a Class A amp design can never be better than 50% efficient and is often closer to 25% efficient or worse. So, if you measure and calculate your amplifier is using 10W to drive your loudspeakers to a given sound pressure level, the amplifier's true power consumption under those conditions might be as much as 40W (possibly more) depending on design used.

Worse still, when you get further down the loopy audiophile path, because these are often designed by one person (who got his or her EE training decades ago, possibly out of a book and a degree mill), you will find arguments like "because Class A is the ideal amplifier, we have used the same uncompromising linear electronics throughout the FartKnocker 6000 amplifier". This means you might end up with a highly inefficient power feed for a display. This is why you can get something like a Krell FBI integrated amplifier, which has a claimed power output of 300W per channel and power consumption ratings of 1.8kW at full tilt, 185W when idle and 70W on standby! I think if you run one of those for a decade, Krell will ship you (for a modest fee) what's left of the polar ice cap, and a free martini glass to store it in.

Power Consumption of Hifi Amplifiers

Reply #14 –
No, I hadn't considered that concern here.

While you mention it, the world is so much class B, that makes a fairly easy rule of thumb for that, at 75% efficient, 25% lost to heat.

Power Consumption of Hifi Amplifiers

Reply #15 –
Gag,
You know I had to re-read your post.  I can say this - that I have recoiled from the power consumption of class A equipment.  Very "ouch", as Austin Powers would say.

I heat my house with propane, not electric.  I suppose if I went with class A, I would tend to look for propane-based amplifiers instead of electric ones.