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Wattage and dB scale

post #1 of 16
Thread Starter 
I know this may be a really stupid question, but I might as well ask to get this out the way.

Amp volume scale 0 - 99 on information display
Amp deliver 100w x 2.
Where is 1. 50w
2. 100w or max. wattage and
3. Clipping on the scale

Or is there no direct relationship?
post #2 of 16
It's not a direct relation nor is it no relation. It is a relative relation to the source.
post #3 of 16
Quote:
Originally Posted by William View Post

It's not a direct relation nor is it no relation. It is a relative relation to the source.
+1. CD's are recorded at different compression rates. A highly compressed CD will play louder w/much less power.smile.gif
post #4 of 16
Quote:
Originally Posted by Heinrich S View Post

I know this may be a really stupid question, but I might as well ask to get this out the way.

Amp volume scale 0 - 99 on information display
Amp deliver 100w x 2.
Where is 1. 50w
2. 100w or max. wattage and
3. Clipping on the scale

Or is there no direct relationship?

No direct relationship, even if the system has been calibrated.

The program material whether music or drama, has a lot to do with the power coming out of the speaker terminals of the amp.

For example, there are commercial recordings where the signal on the media never goes above FS -3 dB. There are others where the recorded signal bangs on FS incessantly. The recording that never goes above -3 dB FS is not going to be able push even a calibrated system to its full rated output power. The 100 wpc power amp is for all intents and purposes limited to 50 wpc.

In uncalibrated system, you can't count on anything. We see people who complain about having to turn their system up to 8 to get it loud enough, and odds are that calibrating some internal trims could turn that around in a dramatic fashion. Furthermore, there is no guarantee that all automated calibration schemes have the same results.
post #5 of 16
Quote:
Originally Posted by Class A View Post

+1. CD's are recorded at different compression rates. A highly compressed CD will play louder w/much less power.smile.gif

It will play louder at a lower volume setting but to achieve a particular spl requires the same power whether the cd averages -3 dBFS or -10 dbfs.
Of course we hear something like the rms as the loudness at any time so if the average is equal the less compressed cd will actually use more power for brief peaks because they may be 10 dB above the average rather than just 3dB as the more compressed cd limits them.
post #6 of 16
You may want to reference what follows to answers I've given to you in other recent threads.
Quote:
Originally Posted by Heinrich S View Post

I know this may be a really stupid question, but I might as well ask to get this out the way.

Amp volume scale 0 - 99 on information display
Amp deliver 100w x 2.
Where is 1. 50w
2. 100w or max. wattage and
3. Clipping on the scale

Or is there no direct relationship?

Let's go through a hypothetical example. Connect a CDP directly to a 100W/8R power amp with nothing in between and connect a set of 90dB/W/8R speakers. With a full scale signal (0dBFS) the CDP outputs 1Vrms, and the power amp needs 1Vrms top produce 1W. Assume they are all perfect for the example.

Put in and play a CD with a recorded 0dBFS test signal. The CDP will output 1Vrms, the power amp will put 28.28Vrms at the terminals and the 8R load will then draw 100W. [P=V²/R = 28.28²/8 = 100W]. As the speaker is 90dB/W and it is getting 100W, then the SPL will be 110dB. As well as power being expressed directly in watts, it can also be expressed in dB referenced to 1W or dBW. 100W is 20dBW [dBW = 10*log(watts/1W) = 10*log(100) = 20dBW]

Now take a recording with a lot of dynamic range, say Beethoven's 9th with the very largest amplitude being encoded at 0dBFS. Averaged across the duration of the piece, the average level is probably something like -30dBFS and the average power into the speakers, 0.1W (80dB SPL), peaking at 110dB SPL and the lowest probably down at 40db SPL or so.

Now change nothing except add a volume control between the CDP and the amplifier. A simple potentiometer could be added into the cable and make a perfectly functioning VC; put this in a box with some connectors and an input selector and you have what is known as a 'passive preamp'. Pots like this tend to be quite non linear, is with every degree of rotation they should produce the same extra dB of attenuation but because of how they're made that is very difficult so they're usually 3 or 4 linear resistances in series that approximate the desired logarithmic function. Another thing to note is that by nature VCs are attenuators, ie, they reduce signal. Assume it's perfect for the example.

Reduce the volume via the VC to -10dB and play the same Beethoven's 9th. Average SPL will now be 70dB, peak 100dB and lowest down around 30dB. I'm sure you can see how it goes if you adjust the VC differing amounts. Now play a CD from the early 80's when some were terrified of digital clipping and the max level anywhere on the CD may be more than 10dB down, so the peak SPL from that disc might be 100dB. Or a recent compressed to hell disc and whilst you'll still get the same 110dB SPL max potential, the average will be much higher even 25W (6dB dynamic range).

Now is where it gets complicated; apart from THX there are and have never been any real standards for signal levels in consumer audio gear. When CD first came out there was what is known as the Red Book CD standard and part of that specified that CDPs should output a level of 2Vrms for 0dBFS, but it was never really enforced and it certainly isn't today so CDPs can and do have quite different output levels: I've personally seen from 1-6Vrms though most are still 1-2Vrms because this is a convenient value. Likewise power amps have varying gains even for the same power output. If the poweramp in the first example above had a gain of 20 instead of 28.28 but was still rated at 100W, you'd never get more than 50W out of it because you aren't supplying it enough signal and so you're output would peak at 107dB instead of 110dB.

If you inserted a commercial preamp into the first example and it had a digital volume display, the display would tell you nothing really useful about SPL. Preamps tend to have some amplification built into them so that you can compensate for that low recorded CD I mentioned earlier, provide more signal out because your poweramp has low gain or to make that old badly recorded cassette you still have loud enough or a combination of all three. The designer makes some guesses about how you might use that system but he can have no idea at all of what you will actually connect to it. A gain of 20x is not uncommon. Referring to the earlier example with the test signal playing in the CDP and the preamp installed, you would have the VC at 20dB attenuation to give full power (unclipped) to the speakers. But how has the designer set the display? Is unity gain -20dB on the display or 80 out of 100 or something else? You can't know without measuring. The best you can do is hope the steps are 1dB on the display so you can get a 'relative' level between 2 settings on the display. If 60 is a comfortable level (display = 0 to 100) that doesn't wake the kids and 80 is your rock out level, any other value will give you an idea of the difference, but not exactly.

AVRs change this a bit. An AVR is the aggregation of the above system: apart from the CD spinner/drive, the DAC, preamp/VC and poweramps are all in the one box. AVRs are usually completely digital: they take analogue sources via an input selector, digitise them through an ADC and send the digital signal to the DSP. Digital signals are the same with the exception of the ADC. All signal processing is done in the DSP, including the volume control. Processed signals are sent to the DACs, power amps and the speakers. Because the unit is now all-in-one the designer now has much more control over the display relative to the signal level. Some AVRs when they measure to do room correction, distance etc can set the display up so that 0dB is reference. But of course it would only play reference (105dB SPL at LP) if the signal was 0dBFS and the speakers were capable of reproducing it.
post #7 of 16
Thread Starter 
Wow, thanks for the reply A9x-308!! eek.gif That explains a whole lot. Makes sense. So it really has more to do with the source, and the volume at which it was recorded, which means one can't calculate how much wattage is being used at a particular MV setting.

I do need to research the calculations and equations you posted, because I don't understand them. Thank you to all who posted, I do appreciate it.

On another slightly unrelated note, a question concerning power supply sections on amps. I took a look at SoundAndVision amp tests and I wanted to ask you guys a question. I looked at Yamaha amps, Denon amps and Onkyos, but for some reason the Yamaha amps post very poor results when running all channels simultaneously on the test bench. Denon and Onkyo models post numbers that are usually much higher.

An example :

Onkyo NR828 ($1099)

2 Channels Continuously Driven, 8 ohm loads 147 watts
2 Channels Continuously Driven, 4 ohm loads 204.4 watts
5 Channels Continuously Driven, 8 ohm loads 109.9 watts

Yamaha A-1020 ($1200)

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 113.5 watts
1% distortion at 129.2 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 63.9 watts
1% distortion at 73.2 watts

Denon E400 ($599)

2 Channels, 8 Ohms 130.0 watts
2 Channels, 4 Ohms 93.3 watts
5 Channels, 8 Ohms 70.0 watts
7 Channels, 8 Ohms 62.3 watts

Yamaha RXV-A730 :

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 115.5 watts
1% distortion at 134.7 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 32.4 watts
1% distortion at 67.2 watts

Seven channels driven continuously into 8-ohm loads:
0.1% distortion at 27.1 watts
1% distortion at 33.3 watts

So my question is, why do the Yamaha amps post such poor numbers in these tests, where the other brands seem to be doing much better?
post #8 of 16
Quote:
Originally Posted by Heinrich S View Post

Wow, thanks for the reply A9x-308!! eek.gif That explains a whole lot. Makes sense. So it really has more to do with the source, and the volume at which it was recorded, which means one can't calculate how much wattage is being used at a particular MV setting.

I do need to research the calculations and equations you posted, because I don't understand them. Thank you to all who posted, I do appreciate it.

On another slightly unrelated note, a question concerning power supply sections on amps. I took a look at SoundAndVision amp tests and I wanted to ask you guys a question. I looked at Yamaha amps, Denon amps and Onkyos, but for some reason the Yamaha amps post very poor results when running all channels simultaneously on the test bench. Denon and Onkyo models post numbers that are usually much higher.

An example :

Onkyo NR828 ($1099)

2 Channels Continuously Driven, 8 ohm loads 147 watts
2 Channels Continuously Driven, 4 ohm loads 204.4 watts
5 Channels Continuously Driven, 8 ohm loads 109.9 watts

Yamaha A-1020 ($1200)

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 113.5 watts
1% distortion at 129.2 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 63.9 watts
1% distortion at 73.2 watts

Denon E400 ($599)

2 Channels, 8 Ohms 130.0 watts
2 Channels, 4 Ohms 93.3 watts
5 Channels, 8 Ohms 70.0 watts
7 Channels, 8 Ohms 62.3 watts

Yamaha RXV-A730 :

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 115.5 watts
1% distortion at 134.7 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 32.4 watts
1% distortion at 67.2 watts

Seven channels driven continuously into 8-ohm loads:
0.1% distortion at 27.1 watts
1% distortion at 33.3 watts

So my question is, why do the Yamaha amps post such poor numbers in these tests, where the other brands seem to be doing much better?

First of, you have data from so few Yamaha amps (only two of the dozens that they have on the market) that it is easy to argue that it is not representative. It may be, it may not.

All of the numbers you collected are irrelevant to the ability of these AVRs to play music loudly without distortion. They all appear to have been collected from bench tests involving pure sine waves, not actual use involving music and loudspeaker loads. Sine waves stress power supplies and heat sinks an absolute minimum of 2 to 4 times harder than music, and multiples of 10 or more are possible. Loudspeaker loads stress power supplies and heat sinks at least 50% harder and up to twice or more.

The worst thing you can say about the Yamaha equipment about whom you gathered the above data is that they are optimized for playing music.
post #9 of 16
Quote:
Originally Posted by A9X-308 View Post

You may want to reference what follows to answers I've given to you in other recent threads.

AVRs change this a bit. An AVR is the aggregation of the above system: apart from the CD spinner/drive, the DAC, preamp/VC and poweramps are all in the one box. AVRs are usually completely digital: they take analogue sources via an input selector, digitise them through an ADC and send the digital signal to the DSP.

True for analog signals but these days there is almost no purely analog media in actual use.
Quote:
Digital signals are the same with the exception of the ADC.

To further clarify, the pervasive nature of digital media for both recordings and broadcasts has vastly changed things. A modern audio system usual brings all media into itself as digital signals. Digital signals have a built-in reference - digital full scale. While the audio may be mastered to different peak levels and compressed or inherently have different average average levels, there is a built in highly accurate and stable reference point: Digital Full Scale (FS).
Quote:
All signal processing is done in the DSP, including the volume control.

Surprisingly not true. Yes, all signal processing is done by one or more DSPs, but volume controls are electronic, digitally controlled, but themselves analog. Therefore they follow the DACs and provide signals to the amplifiers and external line levels outputs, which exist for the subwoofer(s) but may or may not exist for other AVR outputs.
Quote:
Because the unit is now all-in-one the designer now has much more control over the display relative to the signal level. Some AVRs when they measure to do room correction, distance etc can set the display up so that 0dB is reference. But of course it would only play reference (105dB SPL at LP) if the signal was 0dBFS and the speakers were capable of reproducing it.

Excellent point. The mastering of the media can still be anything. It is not uncommon for recordings to peak at -3-4 dB FS. I sometimes find digital files on the web that peak at -10 dB FS, or less.
post #10 of 16
Thread Starter 
Quote:
First of, you have data from so few Yamaha amps (only two of the dozens that they have on the market) that it is easy to argue that it is not representative. It may be, it may not.

I gave you a Yamaha model retailing for $1200, which is well above entry-level, and compared it to a $500 garden-variety spec Denon AVR. I think it is safe to assume that the lower spec Yamaha models below the RX-A1020 would perform at a lower level. Not sure why you want me to post the numbers of all Yamaha AVRs ever made. If the A-730 and A-1020 are such poor performers in these kinds of tests, that should give you some indication of the other models.

Here is the Yamaha RX-V475 ($450) :

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 84.6 watts
1% distortion at 105.9 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 23.6 watts
1% distortion at 27.8 watts

Here is the Yamaha RX-Z7 ($2800)

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 63.0 watts
1% distortion at 66.3 watts

Seven channels driven continuously into 8-ohm loads:
0.1% distortion at 47.1 watts
1% distortion at 54.5 watts


Now that's four models, one costing $450, one costing $700, one costing $1200 and the final one is $2800 - that should give you a very good indication of their performance. A $2800 Z7 performs worse than the $599 Denon E400 in the 5 channel/7 channel testing! That's a basic spec model.

So again, based on this information, why are they performing so poorly in the 5 channels driven test? I understand the testing is not representative of real world use, but brands like Onkyo, Denon and Marantz don't suffer such poor performance in the same tests.
post #11 of 16
They perform that way because they are poorly designed for driving real speakers (as opposed to a resistor). IMO ALL Yamaha receivers are crap, relative to most of the competition. Those numbers certainly reinforce my opinion, but power ratings are not the whole story anyway.

If you look at NAD and Cambridge Audio receivers, you will see that they GIVE honest RMS power specs for ALL CHANNELS DRIVEN, which none of the Yamaha, Pioneer, or Sonys even attempt to give.

The advice I give anyone who has the sense to listen is this; buy a NAD or Cambridge Audio AVR or be satisfied with poorly-designed trash that will not properly drive most speakers and will sound lousy (no matter what the supposed "power rating" may be).

Power ratings alone do not tell the whole story in any case; there are many design factors that determine the ability to drive real-world speakers, and which determine sound quality.

Anyone who goes by power ratings alone is not very smart, because there are many different ways to arrive at a power rating, and most of them are deceptive in that they do not reflect how well the amplifier really drives speakers.

Put a Bryston 150-watt power amplifier next to a "150-watt" Yamaha or Pioneer receiver, and if you can't immediately tell the difference in SOUND QUALITY, you have a serious problem.

Anyone that says all amplifiers with a certain power rating sound the same has never been through engineering school or designed an amplifier; he is totally ignorant of the truth.



The oats is always cheaper after it has been through the horse.


Quote:
Originally Posted by Heinrich S View Post

I gave you a Yamaha model retailing for $1200, which is well above entry-level, and compared it to a $500 garden-variety spec Denon AVR. I think it is safe to assume that the lower spec Yamaha models below the RX-A1020 would perform at a lower level. Not sure why you want me to post the numbers of all Yamaha AVRs ever made. If the A-730 and A-1020 are such poor performers in these kinds of tests, that should give you some indication of the other models.

Here is the Yamaha RX-V475 ($450) :

Two channels driven continuously into 8-ohm loads:
0.1% distortion at 84.6 watts
1% distortion at 105.9 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 23.6 watts
1% distortion at 27.8 watts

Here is the Yamaha RX-Z7 ($2800)

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 63.0 watts
1% distortion at 66.3 watts

Seven channels driven continuously into 8-ohm loads:
0.1% distortion at 47.1 watts
1% distortion at 54.5 watts


Now that's four models, one costing $450, one costing $700, one costing $1200 and the final one is $2800 - that should give you a very good indication of their performance. A $2800 Z7 performs worse than the $599 Denon E400 in the 5 channel/7 channel testing! That's a basic spec model.

So again, based on this information, why are they performing so poorly in the 5 channels driven test? I understand the testing is not representative of real world use, but brands like Onkyo, Denon and Marantz don't suffer such poor performance in the same tests.

Edited by commsysman - 1/19/14 at 9:24am
post #12 of 16
Quote:
Originally Posted by commsysman View Post


Anyone that says all amplifiers with a certain power rating sound the same has never been through engineering school or designed an amplifier; he is totally ignorant of the truth.

Anyone that says that modern, properly designed solid state amplifiers don't the same has no experience with studying hearing bias or is totally ignorant of the truth.
post #13 of 16
Quote:
Originally Posted by Heinrich S View Post

So my question is, why do the Yamaha amps post such poor numbers in these tests, where the other brands seem to be doing much better?

The Harman Kardon AVR 1700 also has low numbers for 5 channels driven, Sound & Vision has done a review of the AVR 3700 (not online yet) and measurements are:

2 channels continuously driven 8 ohm loads: 0.1% THD 151.1 watts, 1.0% THD 170.2 watts
5 channels continuously driven 8 ohm loads: 0.1% THD 37.2 watts, 1.0% THD 40.2 watts
7 channels continuously driven 8 ohm loads: 0.1% THD 27.9 watts, 1.0% THD 33.8 watts
post #14 of 16
Quote:
Originally Posted by commsysman View Post


Put a Bryston 150-watt power amplifier next to a "150-watt" Yamaha or Pioneer receiver, and if you can't immediately tell the difference in SOUND QUALITY, you have a serious problem.

Or maybe it just means that you are not a fool.
post #15 of 16
Quote:
Originally Posted by Badouri View Post
 
Quote:
Originally Posted by commsysman View Post


Put a Bryston 150-watt power amplifier next to a "150-watt" Yamaha or Pioneer receiver, and if you can't immediately tell the difference in SOUND QUALITY, you have a serious problem.

Or maybe it just means that you are not a fool.

 

Notice, actually hooking it up is irrelevant to the improvement in sound quality.

post #16 of 16
If like me you use 10 or 20 watts for peaks the more capable amp like a Bryston will only be audibly different if one or the other is designed to depart from flat response in an audible way.or if they are driving really full range speakers without a sub and the speakers present a difficult load down low. Then the amp with lower output impedance, which is different from power, will perform better.

That Ohm's law thing guarantee that unneeded power has no effect. The physical laws of our dimensions of the universe prevent the more powerful amp from doing anything different at 20 watts than the less powerful amp at 20 watts.
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