What makes a receiver sound better than others??

[PENG]

People were mentioning things like THD and SNR and frequency response. Something else not mentioned, which isn't measured for, is how quickly notes start and stop. I've never seen a measurement for that. But you can make this happen yourself if you stick a resistor in series with the output, I think. Doing so will make voltage transitions take longer.

That is incorrect. A resistor in series will drop the voltage so the load behind the resistor will see a lower voltage.

 

[Josuah]

Something else not mentioned, which isn't measured for, is how quickly notes start and stop.

Yes, but that is a speaker issue. And, with that moving, dynamic music, I bet you would not be able to use that single trait to differentiate components with the same speakers, unless the basic component design is faulty.

No, it's not only a speaker issue. This is why current-based DACs are considered better than voltage ones, IIRC. They can switch much faster. Using all the same gear, you can hear this difference. At least I can. And I don't have crappy gear.

Yes, but visual difference not necessarily translate to audible differences.

The analog output stage that created audible noise for me translated into very minute voltage differences on the oscilloscope. When the DAC output is in the 1Vp-p range, a dozen mV or so will be audible.

That is incorrect. A resistor in series will drop the voltage so the load behind the resistor will see a lower voltage.

Um, yes. That's true, but it'll also have the effect I'm talking about. Take a square wave and run it through a very low resistor like 30 ohms. You'll see the edges of the square wave round off.

 

[mtrycrafts]

No, it's not only a speaker issue. This is why current-based DACs are considered better than voltage ones, IIRC. They can switch much faster. Using all the same gear, you can hear this difference. At least I can. And I don't have crappy gear.
The analog output stage that created audible noise for me translated into very minute voltage differences on the oscilloscope. When the DAC output is in the 1Vp-p range, a dozen mV or so will be audible.
.

Of course this was confirmed through a credible DBT listening evaluation for audible differences?
Or, is the the example when you used your wife?

 

[TLS Guy]

People were mentioning things like THD and SNR and frequency response. Something else not mentioned, which isn't measured for, is how quickly notes start and stop. I've never seen a measurement for that. But you can make this happen yourself if you stick a resistor in series with the output, I think. Doing so will make voltage transitions take longer.

And single-blind level matched testing is fine for me, thank you very much. If I can pick out my eyeglasses using single-blind testing, I can do the same with my gear. Also using two oscilloscope channels in difference mode will be non-flat if the outputs are different.

The analog output on a cheap DVD player is extremely audible. No need for any measurements there. Additional noise coming out of nowhere.

There is a grain of truth in what you say, however it goes to band width, (frequency response and stability). The fact is this is a spec. seldom published these days. This speaks to Seth's thread about dumbing down!

The spec. which always used to be published, is the 1 KHz square wave response. Not only that but the square wave response into inductive and reactive loads typical of loudspeakers. Under these conditions good amps have nice sharp up and down stroke with clean corners and no wiggles across the top and bottom, especially at the corners. This test really sorts them out. I think most receiver manufacturers would rather you didn't know what it looks like, especially into real world loads.

Fortunately for them most of this is hidden in a sea of loudspeaker imperfection.

One thing you can glean from the spec is the ability to provide current to complex loads. This tends to be where receivers really fall short. If a receiver provides 100 watts into 8 ohms, then it should provide 200 watts into four ohms, certainly not activate protection. This is important as speaker impedance ratings are virtually meaningless. There are big dips more often than not in the impedance curve of nominally eight ohm speakers. We had a case recently where the speakers were rated at 8 ohms, bit in fact the impedance dropped as low as 2.9 ohms! The minimum impedance of a speaker is far more significant than the so called nominal impedance, and yet seldom revealed. Not only that in speaker loads voltage and current are not in phase and so current demands are frequently higher than calculations from ohms law would suggest.

 

[Seth=L]

There is a grain of truth in what you say, however it goes to band width, (frequency response and stability). The fact is this is a spec. seldom published these days. This speaks to Seth's thread about dumbing down!

The spec. which always used to be published, is the 1 KHz square wave response. Not only that but the square wave response into inductive and reactive loads typical of loudspeakers. Under these conditions good amps have nice sharp up and down stroke with clean corners and no wiggles across the top and bottom, especially at the corners. This test really sorts them out. I think most receiver manufacturers would rather you didn't know what it looks like, especially into real world loads.

Fortunately for them most of this is hidden in a sea of loudspeaker imperfection.

One thing you can glean from the spec is the ability to provide current to complex loads. This tends to be where receivers really fall short. If a receiver provides 100 watts into 8 ohms, then it should provide 200 watts into four ohms, certainly not activate protection. This is important as speaker impedance ratings are virtually meaningless. There are big dips more often than not in the impedance curve of nominally eight ohm speakers. We had a case recently where the speakers were rated at 8 ohms, bit in fact the impedance dropped as low as 2.9 ohms! The minimum impedance of a speaker is far more significant than the so called nominal impedance, and yet seldom revealed. Not only that in speaker loads voltage and current are not in phase and so current demands are frequently higher than calculations from ohms law would suggest.

This would fall into the category of a receiver being pushed past it's limits. Many of us here understand that speakers don't stay at one particular impedance, as the frequency changes the impedance typically varries as well. You are also correct that many mid to lower level receivers aren't the best equipped to handle lower impedances such as those mentioned. People where always wondering why the Klipsch Reference towers wouldn't sound that great with a typically mid-level receiver, it's because the impedance drops so low that the receiver can't appropriately handle it.

I'm not saying high dollar amplifiers and receivers don't have a place. However, most mid-level receivers are equipped to handle most speakers in most rooms without many problems.

 

[Josuah]

I recall seeing a polar plot of impedance + phase being used to describe the difficulties in driving a speaker. The distance from the center being proportional to the difficulty. I don't remember the exact method of calculating the polar coordinates though.

 

[TLS Guy]

I recall seeing a polar plot of impedance + phase being used to describe the difficulties in driving a speaker. The distance from the center being proportional to the difficulty. I don't remember the exact method of calculating the polar coordinates though.

We have covered this before , but the issue is that when voltage and current are out of phase, always in moving coil loudspeakers, there is stored energy. So there is true power and apparent power. Now the apparent power requires true current delivery, and is true power X cos phase angle. The problem is that the phase relationships are not generally published.

I have to say I think on the whole receivers short change people. I have to say making any amp these days that goes into protection driving a four ohm load is inexcusable.

If you look in the digi-key catalog you find that high current output devices are now very cheap.

I think a lot of the problem is heat, and having amps in the same case as sophisticated microprocessors. Amps just don't belong there. People don't realize that most speakers are complex loads no matter what the nominal impedance is. Having current limited receivers, really is limiting to overall results.

I really feel it is time to retire the receiver to history, in fact I think it's over due. If there was no prior history of receivers and someone came up with idea, they would be laughed off the design team.

Now, no one bats an eyelid that an LFE out is a pre out with no pre in. Subs have the amp in the speaker where it belongs.

I fail to see why it causes people such terrible psychological angst to put all amps in the speaker, one for each pass band and do away with passive analog filters. That really would bring about a big increase in performance.

It is of no help that people continue to put cabling in their walls, including professional installers, not in conduit. If cables are in conduit they can be easily changed. I would propose that the speaker connection be optical digital SDIF, that way ground loop problems would be avoided.

It will be a great pity if powered speakers like those made by ATC remain the province of the high end.

Bottom line NEVER put a cable in your walls that is not in conduit, EVER!

 

[PENG]

Um, yes. That's true, but it'll also have the effect I'm talking about. Take a square wave and run it through a very low resistor like 30 ohms. You'll see the edges of the square wave round off.

A pure resistor offers resistance to current flow, it does not change the waveform, but what you claimed could be true to a point in the sense that nothing is 100% pure, so a resistor is going to offer some inductive and capacitive characteristics. On the practical side, any such effects will be so negligible that it won't be audible to human.

 

[Josuah]

A pure resistor offers resistance to current flow, it does not change the waveform, but what you claimed could be true to a point in the sense that nothing is 100% pure, so a resistor is going to offer some inductive and capacitive characteristics. On the practical side, any such effects will be so negligible that it won't be audible to human.

Hm. I've tried sticking a small capacitor in series with the DAC output, say a dozen uF. That's probably more than what you'd find in a resistor in series, but it didn't sound good at all to me.

The passive analog output stage of the Twisted Pear Opus in its simplest form uses a design like that.

I think a resistor in series that is less than a few hundred ohms might be inaudible though, like you're saying. I should try it some time.