Can a 80 watt receiver put out more than 80 watt?

[ski2xblack]

Most people have more modest power needs, don't you think?

Probably, but it all depends. You cannot mitigate the reality that a +20db peak requires a hundredfold increase in power, so if the average levels are half a watt, the 50 w amp would cover the peaks without clipping. Even if the average level was a wee bit above half a watt, resulting in occasional clipping, it still probably wouldn't matter. My own rigs fall into that territory, I even have the same amp as a couple of you, the AT602. My room is rather large, and I like it loud-ish but not ridiculous, and the speakers I use are north of 95db/w, so it works. So sure, I agree with caveats, as whether there is enough power depends on speaker sensitivity, distances involved, and the listener's preference for spl.

Although he expressed curiosity about the tech side of this, I think these discussions, while germane, are off in the weeds and may have either bored the OP to death or scared him away. @RHD , you still tuning in? Did you get what you were asking for?

 

[AcuDefTechGuy]

I tried to spell that out in my post#32, that it basically depends on the correct interpretation of what you are saying. Would you mind reading that post again and let me know which part I need to clarify further? Thank you for your patience.

If an amp is rated at 100WPC "RMS" or "Average Power" into 8 ohms at 0.1% THD, then Peak Power is 200WPC into 8 ohms at 0.1% THD.

But we don't know what the Clipping THD% is.

Clipping THD% could be 1%, 2%, 3%, etc.

Right?

But there are exceptions. I think the Benchmark amp example shows that Peak Power = Clipping Power = Average Power because regardless of THD%, the output line is almost a vertical line. I think.

 

[ski2xblack]

Clipping THD% could be 1%, 2%, 3%, etc.

Right?

Strictly speaking, clipping is whenever there is any waveform deformation of the peaks, however minuscule, in the output. What matters is what's actually audible. If the THD is characterized by high, odd order harmonics, most listeners can hear 1% THD on pure sine waves, and it makes pure tones sound like a neon sign. Typical class a/b amps, which have been the predominant type in the market for decades, exhibit that high, odd order behavior when clipped, so it makes sense that they use the lowest THD ratings.

But there are exceptions. I think the Benchmark amp example shows that Peak Power = Clipping Power = Average Power because regardless of THD%, the output line is almost a 90 degree vertical line. I think.

I think this goes towards the design of the supply. Fully regulated vs. more loosely regulated result in differences in available headroom and the ability to "double down" into lower impedance loads. That Benchmark looks like it uses the more of the fully regulated type.

 

[mtrycrafts]

If an amp is rated at 100WPC "RMS" or "Average Power" into 8 ohms at 0.1% THD, then Peak Power is 200WPC into 8 ohms at 0.1% THD. But we don't know what the Clipping THD% is.

That is an interesting question and supposition as we can see THD/power plots where THD changes from the smallest signal input to where the plot stops at some THD% and power still increasing. We don't see the sine wave transitioning to a flatter top.
And, perhaps that Benchmark is an interesting example.

Clipping THD% could be 1%, 2%, 3%, etc.

Right? ...

That would be my assumption until better data surfaces.

 

[AcuDefTechGuy]

Strictly speaking, clipping is whenever there is any waveform deformation of the peaks, however minuscule, in the output. What matters is what's actually audible. If the THD is characterized by high, odd order harmonics, most listeners can hear 1% THD on pure sine waves, and it makes pure tones sound like a neon sign. Typical class a/b amps, which have been the predominant type in the market for decades, exhibit that high, odd order behavior when clipped, so it makes sense that they use the lowest THD ratings.

I see.

And for most of us sensible people, we would immediately turn it off or down when we can hear this 1% THD.

But for those other people, clipping could continue at 2%, 3%, etc., which I think @Irvrobinson was saying.

 

[mtrycrafts]

Strictly speaking, clipping is whenever there is any waveform deformation of the peaks, however minuscule, in the output.

Another interesting posit. Plots do not show sine wave deformation, just x%THD. And, THD, however minuscule, happens from the start, no?

What matters is what's actually audible. If the THD is characterized by high, odd order harmonics, most listeners can hear 1% THD on pure sine waves, and it makes pure tones sound like a neon sign. Typical class a/b amps, which have been the predominant type in the market for decades, exhibit that high, odd order behavior when clipped, so it makes sense that they use the lowest THD ratings.

Yes, this would be up to each individual then. Low frequency distortion would be noticed at a different level then midband and high frequency. What a conundrum.

 

[ski2xblack]

And for most of us sensible people, we would immediately turn it off or down when we can hear this 1% THD.

Yes, of course. Fortunately we listen to music, and not pure sine waves! With music, distortion doesn't become audible until a slightly higher %THD than pure tones (higher crest factor mean less clipping for shorter durations, which is far less noticeable) and thankfully manifests at lower power than that gross square wave full blown hard clipping discussed in previous posts, which fries speakers. So you were absolutely correct with an earlier post directed to the OP: if it starts to sound bad, turn it down immediately.

 

[Irvrobinson]

I see.

And for most of us sensible people, we would immediately turn it off or down when we can hear this 1% THD.

But for those other people, clipping could continue at 2%, 3%, etc., which I think @Irvrobinson was saying.

I doubt very much that anyone could hear 1% THD on real program material in a way that makes them want to turn it down. On individual sine waves you can hear it, but on even a single instrument, I doubt it. There used to be a web site that had 1KHz test tone files with 1%, 2%, and 3% THD, but now I can't find it. Even the 3% THD test tone was not as overt as one would expect.

Edit: remember, 1% THD is 40db below the fundamental. So if you play a test tone at 70db, the distortion will be at 30db, which is the background noise level for a very quiet room. 3% THD will be at 40db in the same test.

 

[PENG]

If an amp is rated at 100WPC "RMS" or "Average Power" into 8 ohms at 0.1% THD, then Peak Power is 200WPC into 8 ohms at 0.1% THD.

But we don't know what the Clipping THD% is.

Clipping THD% could be 1%, 2%, 3%, etc.

Right?

But there are exceptions. I think the Benchmark amp example shows that Peak Power = Clipping Power = Average Power because regardless of THD%, the output line is almost a vertical line. I think.

Seem like you missed my post#32, in which I referred to you very point and I stated:

Regarding ADTG's, it could simply be a matter of interpretation. Under the following assumptions, ADTG would be correct.

1. Define clipping as when THD exceeds a defined % level, example: 0.1%.
2. By RMS power, he meant average power the amp is rated for at the defined THD % level mentioned in 1.
3. By 2X RMS power, he meant the peak power that is 2 X the so called continuous RMS power.

If by 2X RMS power he meant whatever the amp is rated in RMS/average power output at the defined THD level considered, clipping wouldn't occur until the RMS/average output exceeded 2X the rated output, then I would disagree with him too.

If you want to reference a % THD as "clipping" that is significant enough to worry about it, then you have to define (arbitrarily unfortunately..) what that % is. To me, 0.1% seems reasonably because when "clipping" is so slight, it is unlikely the resulting THD is going to be offensive, even it is predominantly high order odd harmonics.

So if you are okay with this assumption then let's look at the following example:

You can see that the AVR-X3300W, based on defining clipping as >=0.1% THD, delivered 165 W into 4 ohms, 2 channel driven, using the 1 kHz sweep, or 154 W full bandwidth sweep.

I have to use the 4 ohm graph because Gene did not include the 8 ohm graph.

Since the measured output were "average", i.e. the so called rms, the amp therefore clipped at 2X165 W = 330 W peak. Note that if you define clipping as >= 0.08% THD, the measured output would drop only slightly.

I hope you can see why I said it depends on how we interpret your reference of 2XRMS.

It would be less confusing if you rephrase your point by comparing average/rms to average/rms, or peak to peak. In that case, the DUT is rated 105 W into 8 ohms full bandwidth, and was measured on Gene's bench exactly 105 W, 2 channel driven, at 0.1%, so clipping actually occur at it's rated output, not 2X. You can see it clipped at 2X105, or 210 W, but then the amp was rated 210 W peak to begin with, so still not 2X, just 1X.

As ski said in post#43: "Strictly speaking, clipping is whenever there is any waveform deformation of the peaks.."

If we stick to that factual statement, then your question would become moot.

 

[ski2xblack]

Another interesting posit. Plots do not show sine wave deformation, just x%THD. And, THD, however minuscule, happens from the start, no?

A THD/freq graph doesn't show a waveform at all. You're right about something always being there, but remember that THD graphs are THD+noise, not just harmonic distortion. All amps, even the Benchmark, have at least some noise. Noise dominates THD+N graphs at the far left side and exists throughout. How much nonlinear distortion also occurs down there is not provided.

 

[M Code]

To date the majority of comments & graphs are related to an amplifier clipping into a fixed 8 Ohm resistive load..
Unfortunately a loudspeaker is not a resistor but rather a reactive load which puts a much more complex load on the amplifier compared to a resistor... In my experience we have found that an amplifier may clip @ significantly less than rated power output when driving a highly reactive load. Thats why certain amplifier actually have a LED indicates when an amplifier may be clipping.. This LED circuit basically tracks the top of the wave swing and if corrupted the LED will trigger or flash, that's why many of the experienced amplifier designers use what is called the PowerCube test.. Putting out a certain RMS voltage into an 8 Ohm resistor can be very different than a loudspeaker.. Here is a link to more info from Audio Precision which provides the majority of amplifier test equipment used throughout the world by the major audio brands & testing labs..

https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/
.

Just my $0.02...

 

[PENG]

To date the majority of comments & graphs are related to an amplifier clipping into a fixed 8 Ohm resistive load..
Unfortunately a loudspeaker is not a resistor but rather a reactive load which puts a much more complex load on the amplifier compared to a resistor... In my experience we have found that an amplifier may clip @ significantly less than rated power output when driving a highly reactive load. Thats why certain amplifier actually have a LED indicates when an amplifier may be clipping.. This LED circuit basically tracks the top of the wave swing and if corrupted the LED will trigger or flash, that's why many of the experienced amplifier designers use what is called the PowerCube test.. Putting out a certain RMS voltage into an 8 Ohm resistor can be very different than a loudspeaker.. Here is a link to more info from Audio Precision which provides the majority of amplifier test equipment used throughout the world by the major audio brands & testing labs..

https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/
.

Just my $0.02...

Fair point, but the graph I posted was for a 4 ohm load.

 

[Irvrobinson]

that's why many of the experienced amplifier designers use what is called the PowerCube test.. Putting out a certain RMS voltage into an 8 Ohm resistor can be very different than a loudspeaker.. Here is a link to more info from Audio Precision which provides the majority of amplifier test equipment used throughout the world by the major audio brands & testing labs..

https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/

Ah yes, the Power Cube test. Peter Aczel used to make a big deal out of presenting them in The Audio Critic.

Their bad example is probably a tube amp. I can't imagine a modern solid state amplifier that would measure that way.

 

[M Code]

Fair point, but the graph I posted was for a 4 ohm load.

Noted...
But still it is a resistor not a loudspeaker.
Over the years, I have led amplifier product development teams @ Marantz, JBL, Kenwood, Carver, HK, Onkyo, QSC, Peavey, Crown and had the privilege of interfacing with some of the more noted & visible amplifier designers. They each had their own personalty, uniqueness, design approach & priorities but I learned a great deal from them. But 1 thing that always came up in the equation was the product's FOB cost and the top corporate brass would always ask can we cost it down....

Just my $0.02...

 

[M Code]

Ah yes, the Power Cube test. Peter Aczel used to make a big deal out of presenting them in The Audio Critic.

Their bad example is probably a tube amp. I can't imagine a modern solid state amplifier that would measure that way.

Hmm..
Can't comment much about tube amplifiers as most of my projects were consumer & pro audio Class A-B stuff.. Though over the last 15 years we have jumped into the Class D amplifiers which is a whole different, unique subject..

Just my $0.02...

 

[Irvrobinson]

...the last 15 years we have jumped into the Class D amplifiers which is a whole different, unique subject..

Yeah, I've been a bit fascinated by Class D amps, but they're difficult to study, since most of the implementations appear to be different and proprietary. By comparison, most Class AB look alike (with some obvious exceptions like the Quads, some Thresholds, some Pass amps, and perhaps the Benchmark).

 

[M Code]

Yeah, I've been a bit fascinated by Class D amps, but they're difficult to study, since most of the implementations appear to be different and proprietary. By comparison, most Class AB look alike (with some obvious exceptions like the Quads, some Thresholds, some Pass amps, and perhaps the Benchmark).

IMHO...
Eventually Class D designs will be commonplace in quality home audio systems, they already dominate the subwoofer platforms.. They just offer so many positive things including smaller size, more efficient, higher power per $/LB, lower cost... And in the last 5 years, the Class D amplifier designers have dramatically improved their sonic delivery.. And in todays HT market where more channels and increased power @ a lower cost are expected, Class D will dominate. And for the pro-audio amplifier category Crown, Peavey, QSC have already made the changeover....

Just my $0.02...

 

[mtrycrafts]

...

As ski said in post#43: "Strictly speaking, clipping is whenever there is any waveform deformation of the peaks.."

If we stick to that factual statement, then your question would become moot.

Yes, but. Is deformation of the peak dependent on THD(THD+N?) If so, is that THD arbitrary based on audibility or something else?
Your power plot of that amp has a .08 THD at 2 watts
Would be interesting to also attach a scope and see the sine wave behavior.

 

[PENG]

Yes, but. Is deformation of the peak dependent on THD(THD+N?) If so, is that THD arbitrary based on audibility or something else?

Would be interesting to also attach a scope and see the sine wave behavior.

Agreed, that's why in my earlier response to you (Post#38), I state: "clipping should simply mean as soon as the sine wave cannot reach it's theoretical peak, and that could be low enough that it cannot be seen visually on a scope, without looking at the displayed value.", in trying to make the point ski made later, just differently.

Your power plot of that amp has a .08 THD at 2 watts

I thought you were serious until I noticed the emoticon lol..

You are right though, I was aware of the 2 W at the low end, but I thought everyone would know I was referring to the high end where it shows >150 W.

As we all (or most of us) know by now, class AB amps typically has their THD trending a little higher towards the low end, some would go much higher due to crossover distortions. At very low output level, it should behave much more class A, but even though the XOD is lower, as % it could get much higher due to the low output (the fundamental).

 

[PENG]

Noted...
But still it is a resistor not a loudspeaker.
Over the years, I have led amplifier product development teams @ Marantz, JBL, Kenwood, Carver, HK, Onkyo, QSC, Peavey, Crown and had the privilege of interfacing with some of the more noted & visible amplifier designers. They each had their own personalty, uniqueness, design approach & priorities but I learned a great deal from them. But 1 thing that always came up in the equation was the product's FOB cost and the top corporate brass would always ask can we cost it down....

Just my $0.02...

Agreed previously (long time ago I guess..), and now.. However, I would add that the additional burden an amplifier faced a reactive load is mostly the heat due to higher % of power that has to be dissipated in the output transistors. Obviously if poorly designed there could be other issues, e.g. stability issues. The extra heat issue could be dealt with to certain extent by additional cooling. That's why I always put fans on top of my amps regardless, even my 5 W amp.