What are the most important performance factors you look for in a power amplifier?

[PristineSound]

Several scientific literatures cites that .1% THD+N is the threshold of audibility. I understand that Amir's POV is that if an amplifier manufacturer get their SINAD low, there is a good chance they did everything else right.

Almost no half-way decent, solid state, modern-day power amp has THD+N worse than .1%. Having said all that, what is the top performance factor that you look for in power amplifiers, would you still put THD+N/SINAD as your top choice?

Take the following factors out of the equation:

• Cost
• Aesthetics
• reliability, QA/QC, after sales support
• Brand reputation
• Assume all the options that you won't select aren't egregiously terrible.
• Assume 2-channel stereo power amp. (doesn't matter if it's dual mono or not)

If you think this poll is flawed, not applicable, comment below. I also understand that many of the options below are inter-related.

 

[JPA]

Signal to noise ratio. If I can hear hiss at the speakers when no music is playing, that's a fail.

 

[SIY]

Power, and suitability for the intended load.

 

[PristineSound]

Signal to noise ratio. If I can hear hiss at the speakers when no music is playing, that's a fail.

That would fall under THD+N/SINAD.

 

[Cogito]

Signal to noise ratio. If I can hear hiss at the speakers when no music is playing, that's a fail.

Buy less efficient speakers

 

[Chr1]

Plenty of Watts and cool VU meters

 

[MaxwellsEq]

Can you describe the difference between:

Linear FR and THD+N that are load invariant
Linear FR and THD+N that are frequency invariant

 

[Cbdb2]

Has sufficient current supply if you have low impedance speakers, dost get too hot when driven hard, dosnt make noise, ie dosnt have a fan or a noisy transformer.

 

[PristineSound]

Can you describe the difference between:

Linear FR and THD+N that are load invariant
Linear FR and THD+N that are frequency invariant

Some amplifiers' THD+N and FR changes depending on the frequency and the load impedance.

It's not always X for 20Hz to 20kHz.

 

[MaxwellsEq]

Some amplifiers' THD+N and FR changes depending on the frequency and the load impedance.

It's not always X for 20Hz to 20kHz.

OK I understand the load-sensitivity issue, but I don't understand why "Linear FR and THD+N that are frequency invariant" is different. Both will have a flat frequency-amplitude curve, surely?

 

[rdenney]

Poll: What's most important to you in a car?

1. Engine.
2. Wheels.
3. Steering.
4. Brakes.
5. Seat.
6. Color

That's what I feel like these polls are.

I want enough power to never clip even when playing at the maximum capability of largish speakers. I want enough efficiency to make that power without having to run a separate circuit to power for the heat side effect. I want low enough distortion that I never have to worry about distortion under any circumstances. I want low enough quiescent noise that I can't hear when the amplifier is on, even when the preamp is off.

As to what specifications are important, that's another matter. It seems to me that slew rate is a matter of frequency response at the top of the range. At 20 KHZ, all waveforms are sine waves simply because all the harmonics are filtered out by lack of bandwidth or by the speakers. If the slew rate is sufficient for the zero crossing at 20 KHz, it's good enough. Okay, make it 30 KHz if it makes you feel good.

Stable power supply is the same measure as power output. If the power supply is inadequate, power output will sag and distortion will rise (steeply).

Damping factor is the ability of the amp to avoid being steered by the speakers. It requires very low output impedance. Most amps are abundantly adequate in that regard. But it's a related attribute to being able to preserve frequency response linearity in a range of loading conditions. So, linearity in a range of loading conditions is something I look for.

So, I want an amp with abundant power, low distortion, negligible quiescent noise, and load-invariant linearity. And I want it to be cheap and efficient.

I also want some features not on your list, first and foremost accurate clipping indicators.

But I don't care about aesthetics.

Take away even one of the things I want, and I say no, and it doesn't matter one bit just how good the other features are.

Rick "simplistic" Denney

 

[DWPress]

Totally depends on use. 1000 watts of class H for a sub and .3 distortion is fine vs 30 watts of class AB for an active horn tweeter you are looking at completely different amps.

 

[PristineSound]

Poll: What's most important to you in a car?

1. Engine.
2. Wheels.
3. Steering.
4. Brakes.
5. Seat.
6. Color

That's what I feel like these polls are.

I want enough power to never clip even when playing at the maximum capability of largish speakers. I want enough efficiency to make that power without having to run a separate circuit to power for the heat side effect. I want low enough distortion that I never have to worry about distortion under any circumstances. I want low enough quiescent noise that I can't hear when the amplifier is on, even when the preamp is off.

As to what specifications are important, that's another matter. It seems to me that slew rate is a matter of frequency response at the top of the range. At 20 KHZ, all waveforms are sine waves simply because all the harmonics are filtered out by lack of bandwidth or by the speakers. If the slew rate is sufficient for the zero crossing at 20 KHz, it's good enough. Okay, make it 30 KHz if it makes you feel good.

Stable power supply is the same measure as power output. If the power supply is inadequate, power output will sag and distortion will rise (steeply).

Damping factor is the ability of the amp to avoid being steered by the speakers. It requires very low output impedance. Most amps are abundantly adequate in that regard. But it's a related attribute to being able to preserve frequency response linearity in a range of loading conditions. So, linearity in a range of loading conditions is something I look for.

So, I want an amp with abundant power, low distortion, negligible quiescent noise, and load-invariant linearity. And I want it to be cheap and efficient.

I also want some features not on your list, first and foremost accurate clipping indicators.

But I don't care about aesthetics.

Take away even one of the things I want, and I say no, and it doesn't matter one bit just how good the other features are.

Rick "simplistic" Denney

When I was looking to buy a house, I told my real estate agent, it needs to be 4 bedroom, 3.5 bath, basement, in a great school district, short commute to work, 2 car garage, 3000sqft, oh not older than 20 years old.

The real estate agent came back with tons of options, they were all over $1.5m with a property tax over $25k/year.

Then I said, "You know, I don't need all of that, just in a good school district will do."

I guess because I said take the cost out of the equation, I supposed you can say you want all of that. But the purpose of the poll was trying to figure which performance factor is the absolute most important to you.

 

[rdenney]

When I was looking to buy a house, I told my real estate agent, it needs to be 4 bedroom, 3.5 bath, basement, in a great school district, short commute to work, 2 car garage, 3000sqft, oh not older than 20 years old.

The real estate agent came back with tons of options, they were all over $1.5m with a property tax over $25k/year.

Then I said, "You know, I don't need all of that, just in a good school district will do."

I guess because I said take the cost out of the equation, I supposed you can say you want all of that. But the purpose of the poll was trying to figure which performance factor is the absolute most important to you.

With all due respect, I reject the analogy with respect to amps, because amps that do everything on your list are readily available for not very much money at all in the grand scheme of things. A $700 Buckeye NC502MP isn't the best available but it's better than any amp that was available in my younger years. The power at 500 wpc into 4 ohms (incipient clipping) is abundant, distortion is below the level of human detection, quiescent noise is nonexistent, it uses most of its incoming power to make sound rather than heat (and the moreso the louder it gets), it has a clipping indicator (though if I see it my wife is already throwing a frying pan at my skull), linearity is excellent into the speakers I'm likely to own, and frequency response is dead flat. It would be a dream amp in 1977 when I bought my $125 bottom-of-the-line Kenwood amp--nothing even remotely affordable came close. And yet that Buckeye is the same price as that Kenwood in real dollars. Amps are especially where the relationship between capability and price is completely out of whack, as it is in most areas of the audio world.

Rick "compromising only on aesthetics and brand perception" Denney

 

[RayDunzl]

Lots of available power and inaudible faults fill the bill for me.

 

[MaxwellsEq]

The poll may have been useful in the 1960s, 1970s, 1980s etc. where high power, low noise, low distortion, low output impedance, flat frequency response were often compromises and could only be partially ameliorated by paying a lot. But these days, you can hit all the targets for virtually no money!

The one compromise in the budget space is sustained high output (i.e. greater than 80W) for long periods (where period = more than a few seconds). Solving for this still requires more expense: heavy mass, careful layout and/or fans.

 

[Mnyb]

The poll may have been useful in the 1960s, 1970s, 1980s etc. where high power, low noise, low distortion, low output impedance, flat frequency response were often compromises and could only be partially ameliorated by paying a lot. But these days, you can hit all the targets for virtually no money!

The one compromise in the budget space is sustained high output (i.e. greater than 80W) for long periods (where period = more than a few seconds). Solving for this still requires more expense: heavy mass, careful layout and/or fans.

This +1 the poll really does not cover it . The options seems mutually exclusive when in fact they are not .

Sustained power and longevity and reliability in the long term , may cost you some . But to drive your speakers with ”good enough” sq to please humans should not be that hard to achieve

 

[somebodyelse]

As others have said, there is no single factor. The amp needs to be 'good enough' in multiple areas, while a fail on any of them would disqualify it.

 

[PristineSound]

This +1 the poll really does not cover it . The options seems mutually exclusive when in fact they are not .

As others have said, there is no single factor. The amp needs to be 'good enough' in multiple areas, while a fail on any of them would disqualify it.

The purpose of this poll is trying to figure out what is truly the number most important factor that people look for in an amp, as mentioned in the OP, assuming everything else ain't too shabby and that all factors are inter-related to a certain extent.

 

[somebodyelse]

View attachment 460663

The purpose of this poll is trying to figure out what is truly the number most important factor that people look for in an amp, as mentioned in the OP, assuming everything else ain't too shabby and that all factors are inter-related to a certain extent.

My point is that the poll question is based on a false premise (that there is a single most important factor, when there isn't) so is fundamentally flawed. I'm responding as you asked in the OP:

If you think this poll is flawed, not applicable, comment below.