What makes a high end audio amp "better" then a low end unit?

[Zero999]

Impedance match? Not necessary for audio cables and differences in length of cable between the channels won't matter.

Hun? Non matched left and right impedance speaker cables.  Say you total Left wire is 0.3 Ohm and your Right's total is 0.6 Ohm, with 4 ohm speaker load on each, wont the left be a little louder than the right?

I don't buy that.

I doubt you'll be able to tell the difference between a loss of 7% and 13%, on the left vs right channels, although I'd aim for lower losses than that.

Say you total Left wire is 0.3 Ohm and your Right's total is 0.6 Ohm

That 0.3 Ohm difference equates to 10 meters of 1.5mm² cable. That's more than what most people would have in total.

True. If it's an issue. The answer is thicker cable.

[BrianHG]

Impedance match? Not necessary for audio cables and differences in length of cable between the channels won't matter.

Hun? Non matched left and right impedance speaker cables.  Say you total Left wire is 0.3 Ohm and your Right's total is 0.6 Ohm, with 4 ohm speaker load on each, wont the left be a little louder than the right?

I don't buy that.

I doubt you'll be able to tell the difference between a loss of 7% and 13%, on the left vs right channels, although I'd aim for lower losses than that.

With ease.  Even without a blindfold.  Maybe even with 1 ear covered.
As for aiming for lower loss, yes, 7% & 13% is what should be an impossible extreme.

[oldway]

And the balance setting, what is it for? 

[rdl]

I you go look at high end audio equipment, everything - not just amps, has a lot of money and effort put in to making it look good. I wouldn't be surprised if more is spent on looks than on parts.

[Zero999]

Impedance match? Not necessary for audio cables and differences in length of cable between the channels won't matter.

Hun? Non matched left and right impedance speaker cables.  Say you total Left wire is 0.3 Ohm and your Right's total is 0.6 Ohm, with 4 ohm speaker load on each, wont the left be a little louder than the right?

I don't buy that.

I doubt you'll be able to tell the difference between a loss of 7% and 13%, on the left vs right channels, although I'd aim for lower losses than that.

With ease.  Even without a blindfold.  Maybe even with 1 ear covered.

I doubt it. The ratios between the signal seen at the amplifier and speaker are: R_CABLE = 0.6R = 4/4.6 = 0.8696, R_CABLE = 0.3R 4/4.3 = 0.93, which may seem significant, but human hearing is logarithmic, so it makes more sense to look at it in decibels:  log₁₀(0.8696) = -0.061dB,  log₁₀(0.93) = -0.0315dB, a difference of just 0.03dB. The difference in, audio levels on each track, the sensitivity between the left and right ear, the position of the listener in the room and acoustics will easily exceed a 0.03dB difference in attenuation between channels, caused by the cable.

[oldway]

An audio amplifier is neither more neither less than equivalent to an operational power amplifier
No secrets, nor magic here ....

If a power amp sounds better than another, there must be a parameter of the amplifier that causes it.

What is this parameter?
If there is a difference between two audio power amplifiers, this difference must be measurable because the measuring instruments are more accurate, more sensitive and more reliable than the hearing.

I agree that there are certain differences with regard to preamplifiers: tonal corrections for example ... (bass + trebble or bass + midrange + trebble, correction Db, inflection points, signal / noise ratio , ...)

This topic is full of non technical audiofoolery and of arbitrary and subjective considerations.

[Seekonk]

I have a pair of Magnaplaner speakers.  When I still had good hearing, there was no noticeable difference between a really cheap amp and an expensive one using them.  The Magnaplaner speakers are almost pure resistance.  Few amps handle inductance well.

[oldway]

Few amps handle inductance well. Speakers have a low value inductance (low value because there is a gap between the coil and the magnet) in serie with a large value resistance. They are mostly resistive.

[Seekonk]

Perhaps I should have said motor, same thing.  Anyway, speakers are not resistors.

[oldway]

Few amps handle inductance well.What do you means with this ? Can't "handle" a complex load like a speaker ? An audio amplifier is designed to "handle" a load like a speaker....A transistor amplifier has a voltage feedback, so the kind of load does not matter.
What's the problems ? Instability ? Oscillations ? Never measure anything like this ?

[coppice]

Few amps handle inductance well.What do you means with this ? Can't "handle" a complex load like a speaker ? An audio amplifier is designed to "handle" a load like a speaker....A transistor amplifier has a voltage feedback, so the kind of load does not matter.
What's the problems ? Instability ? Oscillations ? Never measure anything like this ?

Instability is a common issue with power amps and complex loads. It doesn't just affect speaker amps. Even little headphones amps frequently have problems. Plug one pair of headphones in and they sound great. Plug a different model of headphones in and it sounds like someone blowing raspberries. Plug those headphones into a different model of amp and they sound great. This issue is very common with notebook computers. A notebook might not be the first thing you'd go to for super hi-fi results, but the sound some notebook + headphone combinations produce is really awful.

[IanMacdonald]

There is no question that amplifiers do sound different. One of the most offputting kinds of sound artifact is sibilance on vocals, and whilst you might think it results from too much snake oil being put in, it actually results from a tendency to parasitic oscillations when excited at a critical frequency. It is hard to measure such things on the test bench, and they don't show up in specifications.

It is often described as the sound being 'too bright' and is a reason for preferring valves over solid state.

I don't think this is a failing of transistors themselves, rather it is a side effect of specmanship -Designing amps that have the best possible paper specs at the expense of poor HF stability.

Quad equipment is noted for its smooth sound, and I think one reason is that they don't try to achieve silly HF responses. (22kHz is the rolloff IIRC)

[oldway]

Few amps handle inductance well.What do you means with this ? Can't "handle" a complex load like a speaker ? An audio amplifier is designed to "handle" a load like a speaker....A transistor amplifier has a voltage feedback, so the kind of load does not matter.
What's the problems ? Instability ? Oscillations ? Never measure anything like this ?

Instability is a common with power amps and complex loads. It doesn't just affect speaker amps. Even little headphones amps frequently have problems. Plug one pair of headphones in and they sound great. Plug a different model of headphones in and it sounds like someone blowing raspberries. Plug those headphones into a different model of amp and they sound great. This issue is very common with notebook computers. A notebook might not be the first thing you'd go to for super hi-fi results, but the sound some notebook + headphone combinations produce is really awful.

Give me some examples of commercial audio amplifiers with transistors that are unstable when connected to speakers .... I'm curious, I've never met .... tube amplifiers, okay, they are inherently unstable because of the phase shift of the transformer, but the amplifiers with transistors, no.

[oldway]

There is no question that amplifiers do sound different. One of the most offputting kinds of sound artifact is sibilance on vocals, and whilst you might think it results from too much snake oil being put in, it actually results from a tendency to parasitic oscillations when excited at a critical frequency. It is hard to measure such things on the test bench, and they don't show up in specifications.

It is often described as the sound being 'too bright' and is a reason for preferring valves over solid state.

....

This is another subject: the difference between a tube amplifier and a transistor amplifier.

A transistor amplifier behaves like a voltage source. Because of its high feedback rate, it maintains its output voltage equal to that of the input signal.
It does not control the current that passes through the speakers, it imposes the voltage on their terminals.

We all know that if we apply for example a square wave to a partially inductive load, the current will not be a square wave.
But the displacement of the membrane tends to follow the current's value.
There is therefore a weakness of the transistor amplifier on this point.

The tube amplifier behaves more like a current source, in particular because of its low rate of feedback and its high internal impedance. (low damping factor)

It is an essential difference between these two technologies that explains the difference in sound between the two and it is perfectly measurable, by measuring the internal resistance of the amplifier and its damping factor.

[Kleinstein]

Usually audio amps, like other low output impedance amps have no problem with inductive load. They can have a problem with a capacitive load. This especially true for amps build with super high feedback to get super low distortion up to frequencies in the 100 kHz range. Modern amps should handle all load swell, there is no real magic in getting this. A usual element to make it happen is an RL filter at the output.

An inductive load might become a problem when the amplifier is going into clipping or current / SOA limiting. At that level sound is terrible and usually way to loud anyway. I poor designs this might lead to damage to the amplifier.

With conventional speakers it is the cross over circuit that can make the impedance look odd, inductive and capacitive depending on the frequency. In a few nasty cases the load might also be nonlinear from inductors going close to saturation - but that would a fault of the speakers.

The one point where amps can be slightly different is output impedance - usually it should be low, as a low impedance source can dampen resonances of he speakers and tolerate a nonlinear load better. So a good amplifier should be at low impedance end.

However with passive crossover, the crossover circuit will usually dominate the impedance seem by the speaker drivers. To get the low impedance really to the separate speakers it takes active crossover - at least it is much easier that way. Some of the speakers / cross over networks (especially older ones) may be made to work better with a higher impedance amps. So a high output impedance and thus not really good amplifier might sound better. 

This is especially true when comparing with tube amps - they are generally high output impedance and thus are made for different sets of speakers.  So the speakers should be separated in those made for tube amps and those for transistor amp - the wrong combination is not a good idea.

[oldway]

I agree, I would add that the more the cross over is simple, the better it is.

What I like most is the 2-way system, a 12-inch dual cone speaker for bass and midrange and one or more tweeters for trebles.
The crossover is a simple unpolarized capacitor to protect the tweeter (s) against low frequency.

[Fungus]

Nowadays they make Class-D amplifiers with a single chip (digial input) 100+W output and <0.01% THD+N.  I dont even understand why there are amplifiers anymore. Seems so pointless. I believe that good quality active speakers are the way to go.

Yep. Class D has come on in leaps and bounds over the last decade. All the old class A and AB stuff is pretty much obsolete.

Modern MOSFETs mean class D amps can be amazingly efficient. Tiny sub-$10 chips can power big powerful systems with almost zero THD.

eg. http://www.ti.com/product/TPA3255/datasheet

So yeah, amplifier problem is solved. Look at speakers and room acoustics instead.

[Alex Nikitin]

After reading this thread I would like to ask - how many of "Oh it is so easy, Class D makes old technology obsolete, everything was solved 50 years ago" commentators did actually design a decent hi-fi amplifier for production? 

Cheers

Alex

[Zero999]

There is no question that amplifiers do sound different. One of the most offputting kinds of sound artifact is sibilance on vocals, and whilst you might think it results from too much snake oil being put in, it actually results from a tendency to parasitic oscillations when excited at a critical frequency. It is hard to measure such things on the test bench, and they don't show up in specifications.

It is often described as the sound being 'too bright' and is a reason for preferring valves over solid state.

....

This is another subject: the difference between a tube amplifier and a transistor amplifier.

A transistor amplifier behaves like a voltage source. Because of its high feedback rate, it maintains its output voltage equal to that of the input signal.
It does not control the current that passes through the speakers, it imposes the voltage on their terminals.

We all know that if we apply for example a square wave to a partially inductive load, the current will not be a square wave.
But the displacement of the membrane tends to follow the current's value.
There is therefore a weakness of the transistor amplifier on this point.

The tube amplifier behaves more like a current source, in particular because of its low rate of feedback and its high internal impedance. (low damping factor)

It is an essential difference between these two technologies that explains the difference in sound between the two and it is perfectly measurable, by measuring the internal resistance of the amplifier and its damping factor.

Are you sure that the position of the speaker's cone is proportional to the current, rather than the voltage?

I thought, it's better to use a voltage source to drive the speakers, rather than a current source, because it damps the resonance. It's easy to make a solid state amplifier with a constant current output. I've never made one and tested it on real speakers though.

[oldway]

I dare not venture into the subject "speakers" because I am not a specialist in this matter.

But I find that many of my customers prefer the sound of a tube amplifier rather than transistors.

I think our ears may not prefer the most perfect sound ....

Looking to reproduce a perfect sound is perhaps not the best solution.

A transistor amplifier actually tends to force the speaker diaphragm to follow the signal.
But perhaps that makes the sound of a transistor amplifier drier, colder than that of a tube amp.
With a tube amp, the membrane is freer, it can vibrate according to its own resonances ...

Where is the right solution in all this? I do not know but I find that many of my customers prefer the sound "Tubes".

NB: see the Philips Motional Feedback Speakers.....

http://hifipig.com/philips-motional-feedback-speakers/

Also modifications of transistor amplifiers for current drive of speakers.

https://www.current-drive.info/9

I thought, it's better to use a voltage source to drive the speakers, rather than a current source, because it damps the resonance.

Today, all commercially available audio amplifier and loudspeaker equipment works on voltage drive principle without significant exceptions. This means that the amplifier acts as a voltage source and therefore exhibits low output impedance. Thus, the amplifier as though forces the voltage across the load terminals to follow the applied signal without any regard to what the current through the load will be.

However, both technical aspects and listening experiences plainly indicate that voltage drive is the wrong choice if sound quality is of any importance. The fundamental reason is that the vague electromotive forces (EMF), that are generated by both the motion of the voice coil and its inductance, seriously impair the critical voltage-to-current conversion, that in the voltage drive principle is left as the job of the loudspeaker.

https://www.current-drive.info/6

[Fungus]

After reading this thread I would like to ask - how many of "Oh it is so easy, Class D makes old technology obsolete, everything was solved 50 years ago" commentators did actually design a decent hi-fi amplifier for production? 

I never said it was "easy", I said it was "solved".

Whatever your feelings are about class D, this isn't the 1970s. Awesome parts are cheap and readily available. Reference designs abound. There's no need to "design" anything.

[Johnny10]

I think it all goes back to the OP Beamin...
He is an instigator !

[Alex Nikitin]

After reading this thread I would like to ask - how many of "Oh it is so easy, Class D makes old technology obsolete, everything was solved 50 years ago" commentators did actually design a decent hi-fi amplifier for production? 

I never said it was "easy", I said it was "solved".

Whatever your feelings are about class D, this isn't the 1970s. Awesome parts are cheap and readily available. Reference designs abound. There's no need to "design" anything.

Well, if you are OK with a crap sound, there is indeed no need  . Fortunately for manufacturers of that crap the majority of consumers don't give a #**! about the sound quality. Especially as it is "scientifically proven" that it does not matter.  And so it goes. I am quite happy to be in a minority who cares about quality sound.

Cheers

Alex

[Circlotron]

Are you sure that the position of the speaker's cone is proportional to the current, rather than the voltage?

I thought, it's better to use a voltage source to drive the speakers, rather than a current source, because it damps the resonance. It's easy to make a solid state amplifier with a constant current output. I've never made one and tested it on real speakers though.

After experimenting with this a bit on and off over the years I came to the conclusion that the voice coil *velocity* is proportional to the instantaneous signal voltage, and the voice coil *force* is proportional to the current. Voice coil instantaneous position is indeterminate because of suspension compliance, acoustic loading etc.  My opinion is that the ideal setup would be current drive to the voice coil and motional feedback. Kind of similar to current mode control in a SMPS - it completely takes an unknown voice coil position out of the loop.

[Circlotron]

And what complicates this further is if a dynamic mic was used in the original recording then peak signal voltage occurs at the mechanical zero crossing of the mic diaphragm whereas if a condenser mic was used then peak signal voltage occurs at max diaphragm excursion.