Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-24 Thread Bill Unruh
On Sat, 24 Nov 2007, Darrell Bellerive wrote:

> On Friday 23 November 2007 10:35, Bill Unruh wrote:
>> On Fri, 23 Nov 2007, Gene Heskett wrote:
 On 2007.11.22 at 17:54:19 -0800, Darrell Bellerive wrote next:
> Also while the Audiophile 24/96 does sample at 96 KHz, the audio
> bandwidth of the card is limited to 22 Hz to 22 KHz +/- 0.4 dB.
>> Of course there is no aliasing problem at sampling at 96K and having the
>> frequency go up to 40K. There is an aliasing problem if you then
>> downconvert that to 48K or 44.1K but surely the downconverter should handle
>> that not the soundcard. Mind you why you want more than 22K I have no idea.
>> For sound sources, that is all that you can hear. (NOt me, my ears are old
>> and have trouble with 10K, but if you have little children they might
>> appreciate the extra few KHz, but probably not since they already have to
>> tune out that annoying 15.7KHz scream from the TV.
>
> I use the audio card as a spectrum analyzer for electronics work. By mixing
> radio frequency (RF) signals down to audio frequencies, one can look at a
> section of the RF spectrum. For some tests, the wider the bandwidth the
> better.
>
> Baudline, a great audio analyzer application, will handle sampling rates as
> high as 192 kHz. An analog channel that was flat from 0 Hz to 96 KHz would be
> wonderful. Not to mention a card with a very low noise floor, excellent
> dynamic range, and extremely low distortion.
>
> Now if only such a sound card existed .

Spectrum analysers for the PC deliver far bigger bandwidths than that. Of
course you probably want to go on the cheap and use a sound card, rather
than buy a spectrum analyser card. Going on the cheap means you accept the
limitations. For sound spectra which is what sound cards are for, a cutoff
at 22KHz is very sensible, since almost all sounds are mixed down to CD
quality and the aliasing distortion is attrocious if not properly taken
care of.

So, stop looking at sound cards. 
(Now of course if your interest was dolphin or whale or bat sounds, a far
wider range would be nice, but consumer grade items are unlikely to cater
to that audience.)


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Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-24 Thread Darrell Bellerive
On Friday 23 November 2007 10:35, Bill Unruh wrote:
> On Fri, 23 Nov 2007, Gene Heskett wrote:
> >> On 2007.11.22 at 17:54:19 -0800, Darrell Bellerive wrote next:
> >>> Also while the Audiophile 24/96 does sample at 96 KHz, the audio
> >>> bandwidth of the card is limited to 22 Hz to 22 KHz +/- 0.4 dB.
> Of course there is no aliasing problem at sampling at 96K and having the
> frequency go up to 40K. There is an aliasing problem if you then
> downconvert that to 48K or 44.1K but surely the downconverter should handle
> that not the soundcard. Mind you why you want more than 22K I have no idea.
> For sound sources, that is all that you can hear. (NOt me, my ears are old
> and have trouble with 10K, but if you have little children they might
> appreciate the extra few KHz, but probably not since they already have to
> tune out that annoying 15.7KHz scream from the TV.

I use the audio card as a spectrum analyzer for electronics work. By mixing 
radio frequency (RF) signals down to audio frequencies, one can look at a 
section of the RF spectrum. For some tests, the wider the bandwidth the 
better.

Baudline, a great audio analyzer application, will handle sampling rates as 
high as 192 kHz. An analog channel that was flat from 0 Hz to 96 KHz would be 
wonderful. Not to mention a card with a very low noise floor, excellent 
dynamic range, and extremely low distortion.

Now if only such a sound card existed .

-- 
Darrell Bellerive

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Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-23 Thread Gene Heskett
On Friday 23 November 2007, Bill Unruh wrote:
>On Fri, 23 Nov 2007, Gene Heskett wrote:
>> On Friday 23 November 2007, Vladimir Mosgalin wrote:
>>> Hi Darrell Bellerive!
>>>
>>> On 2007.11.22 at 17:54:19 -0800, Darrell Bellerive wrote next:
 I have never been happy with this card. While it works okay for playing
 basic sound, getting it to do anything more sophisticated is pure black
 magic. For example, I have never gotten full duplex to work.
>>>
>>> Well now, when pulseaudio era came, hopefully it's not true anymore.
>>>
 Also while the Audiophile 24/96 does sample at 96 KHz, the audio
 bandwidth of the card is limited to 22 Hz to 22 KHz +/- 0.4 dB.
>>>
>>> How does that matter when all is needed is digital output?
>>>
>>> Anyway, in analog mode, are you sure there is no option to switch off
>>> bandwidth filter?
>>
>> No one in their right mind would want to do that as the aliasing would
>> drive you up a wall.  The other delay distortions the filter might give
>> are 100's of times more tolerable to listen to.
>
>Of course there is no aliasing problem at sampling at 96K and having the
>frequency go up to 40K. There is an aliasing problem if you then
>downconvert that to 48K or 44.1K but surely the downconverter should handle
>that not the soundcard. Mind you why you want more than 22K I have no idea.
>For sound sources, that is all that you can hear. (NOt me, my ears are old
>and have trouble with 10K, but if you have little children they might
>appreciate the extra few KHz, but probably not since they already have to
>tune out that annoying 15.7KHz scream from the TV.
>
I'm 73, and my ears aren't in that good a shape.  The last time I was tested I 
had a Carhart notch over 120 db deep at 4 kilohertz, rising back up to about 
15 db down at around 7khz, and another notch at 15.735 khz about 40 db deep, 
but then I was the CE at a tv station for around 30 years, with 10 to 25 
monitors in the control room, all screaming at or about that frequency, you 
can hear the doppler shift as the satellite carrying the signal wanders 
around in it box in the sky, and it was back up to about -20 db at 22 khz.  I 
can still hear that stuff very plainly as I also have many years of using SSB 
on chicken band radio where cheap filters let a lot of the opposite sideband 
thru.  So if those badly worn ears can hear and identify it, pity the child 
who hasn't yet worn out 3 centerfire rifle barrels before he figured he'd 
better be wearing some earmuffs.  That BTW is the cause of the Carhart Notch.

>-
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-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Mix's Law:
There is nothing more permanent than a temporary building.
There is nothing more permanent than a temporary tax.

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Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-23 Thread Bill Unruh
On Fri, 23 Nov 2007, Gene Heskett wrote:

> On Friday 23 November 2007, Vladimir Mosgalin wrote:
>> Hi Darrell Bellerive!
>>
>> On 2007.11.22 at 17:54:19 -0800, Darrell Bellerive wrote next:
>>> I have never been happy with this card. While it works okay for playing
>>> basic sound, getting it to do anything more sophisticated is pure black
>>> magic. For example, I have never gotten full duplex to work.
>>
>> Well now, when pulseaudio era came, hopefully it's not true anymore.
>>
>>> Also while the Audiophile 24/96 does sample at 96 KHz, the audio bandwidth
>>> of the card is limited to 22 Hz to 22 KHz +/- 0.4 dB.
>>
>> How does that matter when all is needed is digital output?
>>
>> Anyway, in analog mode, are you sure there is no option to switch off
>> bandwidth filter?
>
> No one in their right mind would want to do that as the aliasing would drive
> you up a wall.  The other delay distortions the filter might give are 100's
> of times more tolerable to listen to.

Of course there is no aliasing problem at sampling at 96K and having the
frequency go up to 40K. There is an aliasing problem if you then
downconvert that to 48K or 44.1K but surely the downconverter should handle
that not the soundcard. Mind you why you want more than 22K I have no idea.
For sound sources, that is all that you can hear. (NOt me, my ears are old
and have trouble with 10K, but if you have little children they might
appreciate the extra few KHz, but probably not since they already have to
tune out that annoying 15.7KHz scream from the TV.

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Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-23 Thread Gene Heskett
On Friday 23 November 2007, Vladimir Mosgalin wrote:
>Hi Darrell Bellerive!
>
> On 2007.11.22 at 17:54:19 -0800, Darrell Bellerive wrote next:
>> I have never been happy with this card. While it works okay for playing
>> basic sound, getting it to do anything more sophisticated is pure black
>> magic. For example, I have never gotten full duplex to work.
>
>Well now, when pulseaudio era came, hopefully it's not true anymore.
>
>> Also while the Audiophile 24/96 does sample at 96 KHz, the audio bandwidth
>> of the card is limited to 22 Hz to 22 KHz +/- 0.4 dB.
>
>How does that matter when all is needed is digital output?
>
>Anyway, in analog mode, are you sure there is no option to switch off
>bandwidth filter?

No one in their right mind would want to do that as the aliasing would drive 
you up a wall.  The other delay distortions the filter might give are 100's 
of times more tolerable to listen to.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Pie are not square.  Pie are round.  Cornbread are square.

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Re: [Alsa-user] "best" card for "bitperfect" S PDIF I/O with external clock sync ?

2007-11-23 Thread Paolo Saggese
On Thursday 22 November 2007 21:01, Vladimir Mosgalin wrote:

> > I meant "M-Audio Revolution 7.1, and quite possibly M-Audio Revolution 5.1
> > allow you to use external clock source.
> 
> In theory, yes. In practice, I wasn't able to make my M-Audio Audiophile
> USB get clock from external source. Well it kinda works, but at some
> point distortions appear, and one must force clock resync or something
> like that by turning card off and on.

mmh... I guess the USB interface may be the problem source here.

Though USB could be operated in asynchronous mode, AFAIK most (all?) 
of the current USB audio devices operate it in synchronous mode, with
the clock provided from the PC.

Of course, if the USB interface (from which the digital audio stream 
is coming) is operated synchronously with source-based clock, then the
sound card MUST be somehow in sync with that stream clock... 

The only way to "loosen" the sync with that clock and try to sync to
another one is to do some sort of reclocking, but unfortunately that 
is not gonna work quite well.
In particular when the "upstream" clock is that of an USB connection 
which - apart from being usually "dirt" and not so stable - is at odd 
rates with respect to audio clocks.

The only real solution would be a sound card which connect to the PC 
through an _asynchronous_ interface (be it USB, firewire, Ethernet, 
HDMI or whatever else, as long as it's fast enough and asynchronous).

BTW, do you know if any such device exists?


> I wanted to create setup similar to this, and one of the things I learned that
> in order to reduce jitter, you'd want to have power as clean as possible.

indeed, absolutely.

> On-board soundchips produce lowest quality signal, pci/pcie boards have much
> better filtering and produce better signal, but if you want something better,
> you have to use card which isn't powered by PSU of your PC, and doesn't suffer
> from problems of its signal. So if you want best digital audio, you probably
> should look among external cards (usb/firewire) which aren't bus powered, and
> use external AC adapter. Interface doesn't matter as long as card doesn't get
> power from it, so choose most compatible card.

well, I have to disagree here. Interface would/should not matter 
ONLY if it is asynchronous. 

If the interface is synchronous, then the card has to lock itself
to the interface clock and, unfortunately, IMHO/IME no reclocking 
and/or resampling will ever be able to really clean up the mess.

For the USB, the standard bus clock frequency makes things even 
worse... don't know about firewire.


Ciao,
Paolo.

--
Skype: Paolo.Saggese
http://borex.lngs.infn.it/saggese
You can still escape from the GATES of hell: Use Linux!

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