How High of a Sample Rate is Enough?

[Fitzcaraldo215]

Incidentally, JA has an interesting article in Septermber's Stereophile, but it is more on A-D performance, but also digital filters, hirez, and on MQA. Provocatively, he connects Charles Hansen and Robert Stuart, apparent enemies, in terms of parallels in sonic effects of their filter philosophies.

One main point, with which I think I agree, is that higher sampling rates lessen the audibility of some adverse effects of digital filters, particularly in the time domain.

Also, Kal has some interesting reviews and comments, as always. Plus, there are the usual, informative JA measurements of gear, some rather poor to mediocre.

 

[March Audio]

Right. And a bandlimited square wave is a series of sines waves up to the cut-off freq. That's ok, but there should not be any artifacts, which isn't easy for digital generators (see this AP article). I have a nice, cheap signal generator app which is great for sine waves and noise, but the square waves are full of aliasing, so useless. I'm not a DSP engineer, but apparently it's not easy to do properly. Perhaps Amir can generate a nice square wave with his new AP ?

Well obviously the harmonics that are generated need to be of the correct level, but what are we using square waves for in audio? It's an artificial signal. If you are concerned about the quality of square wave generation for test purposes, just generate a signal with bunch of sine waves, with some that stretch into the ultrasonic region.

If we are talking about instruments that do have harmonics that stretch above the notional 20kHz hearing limit, I don't see the issue. You can't hear those harmonics, your ears have filtered them. Not to mention that the microphones used rarely have responses above 20kHz, let alone your speakers. You only have to analyse a few 24/96kHz recordings to realise there is rarely anything at any level (apart from noise) above 20kHz.

So my view is that unless aliasing or IM occurs at significant levels within your audible range, you won't hear a difference

 

[March Audio]

OK here are 2 files one a fundamental at 800Hz and the other 800Hz plus ultrasonic tones. Can you hear the difference? Obviously you will need to test blind with something like Foobar ABX. I haven't tried this myself yet.

http://alanmarch.asuscomm.com:5000/sharing/1HGUv7l2G

As replayed on my Motu 8A

Whilst there is some very low level IMD around the ultrasonic tones (+-800Hz sidebands), the in band is very clean.

 

[Krunok]

Something you can try with the signals I prepared is on those where your sons heard differences reduce the level a few decibels and see if they still hear a difference. The threshold for those higher harmonics like at 22 khz would be rather high. So reducing the signal say 10 db might then prevent them from hearing a difference as the higher frequency probably won't be heard by them at reduced loudness.

Do you mean that I play the file at lower level or that I reduce the level of 22kHz signal in the file?

 

[restorer-john]

...but what are we using square waves for in audio? It's an artificial signal...

For amplifier testing- low frequency behaviour, stability, HF response, slew rate, rise times, etc.

If you are concerned about the quality of square wave generation for test purposes, just generate a signal with bunch of sine waves, with some that stretch into the ultrasonic region.

Or use an analogue signal generator- their square waves are about as perfect as they get for my purposes.

 

[March Audio]

For amplifier testing- low frequency behaviour, stability, HF response, slew rate, rise times, etc.



Or use an analogue signal generator- their square waves are about as perfect as they get for my purposes.

All very true of course, but I sort of meant in the context of US audibility as the discussion.

 

[restorer-john]

but I sort of meant in the context of US audibility as the discussion.

Fair enough. Nobody wants to listen to the damn things and they sure don't exist in nature.

I tell you what though, an amplifier that shows me a signal (square wave) that looks like the one that went in, is one I want to listen to.

 

[Krunok]

I tell you what though, an amplifier that shows me a signal (square wave) that looks like the one that went in, is one I want to listen to.

And why would I want an amplifier with frequency range higher than say 30kHz? What's to listen above that?

Unless of course you like to start your day by listening "Best of Square Waves - Vol. 1".

 

[Wombat]

And why would I want an amplifier with frequency range higher than say 30kHz? What's to listen above that?

Unless of course you like to start your day by listening "Best of Square Waves - Vol. 1".

Huh?

 

[solderdude]

And why would I want an amplifier with frequency range higher than say 30kHz? What's to listen above that?

You would want an amplifier to not have any roll-off nor phase shifts in the audible band.
To achieve this the cut-off points will need to be well outside of the audible range.
This means a frequency response well below and well above the audible range.
This has nothing to do with sample rates though.

 

[Krunok]

You would want an amplifier to not have any roll-off nor phase shifts in the audible band.
To achieve this the cut-off points will need to be well outside of the audible range.
This means a frequency response well below and well above the audible range.
This has nothing to do with sample rates though.

Sure, but usually say 70kHz is sufficient to do that, which is still far from enough to cope with square signal.

 

[March Audio]

Fair enough. Nobody wants to listen to the damn things and they sure don't exist in nature.

I tell you what though, an amplifier that shows me a signal (square wave) that looks like the one that went in, is one I want to listen to.

Well I suppose that's mostly about bandwidth. Where do you personally place limits and why?

 

[solderdude]

Sure, but usually say 70kHz is sufficient to do that, which is still far from enough to cope with square signal.

But why would one want to reproduce something that does not exist in nature (square wave) nor is it present in any existing recording.
Microphones nor speakers able to record and reproduce such signals as well.

The only devices capable of reproducing such a signal are filter-less NOS DAC's.
And they should not be able to produce such as it does not exist in any recording.

It is only an artificial signal that shows limits and behavior of amplifiers. It does not have to be perfect, just good enough.

 

[Krunok]

It is only an artificial signal that shows limits and behavior of amplifiers. It does not have to be perfect, just good enough.

I'm an electrical engineer so that's clear to me. But he didn't say "good enough", he said: " an amplifier that shows me a signal (square wave) that looks like the one that went in", and in my eyes this is unreasonably high requirement that is completely unnecessary.

 

[DonH56]

Unless it is ideal, a square wave does not have infinite bandwidth nor zero raise/fall time. I think we can take a step back and recognize a reasonable response, both written in a post here, and in an amplifier's square-wave response.

A 100 Hz square wave does not have much energy up at 10 kHz and above and is close enough to ideal for me. Not sure except just for "fun" or to debug an oscillation/stability issue that I have ever applied a square wave above 1 kHz for that matter. The input is typically bandlimited, either by the generator itself or by a filter someplace after (external or within the component). I want a fast (but bandlimited to maybe 20-40 kHz) edge and then long flat-top both to see the LF behavior and to provide an area to see if any unwanted wiggles happen after that fast edge.

You may be thinking of applying a square wave with fundamental frequency up near the top of the audio band; that is not used IME (except in the aforementioned debugging case).

FWIWFM - Don

 

[mikehoopes]

I also mostly listen to rock and jazz music but I rarelly go to concerts so recreating the "space" is not really my thing. Besides, I don't really think that jazz and rock music can be compared with classical in terms of necessary "space" in concerts.



I share your opinion. Only the most expensive movie productions seems to make a decent usage of the surround technology.

Even then, the surround effects often call attention to themselves. I did enjoy the experience of watching "A Ghost Story", with the Windows 10 Dolby Atmos Headphone spatializer handling the 5.1-channel emulation, despite the lack of Atmos encoding on that particular Amazon stream. I thought the sound design was well-done, with generous, yet tasteful use of the whole sound field.

 

[watchnerd]

Also this BS of upsampling makes little sense to me. Taking a 16/44 and upsampling it to 24/192 or 8xDSD will not add magical or missing data.

But but...khz vs Mhz, dude!