Linux Audio the way to go!?

[soundcheck]

@ mafro

as mentioned earlier in the thread:

Brutefir I use as a sound engine and crossover.
And of course digital volume control.
I wrote my own little player, a wrapper script, which uses brutefir
as an engine.


@ peufeu

Good to see you over here again. How are you doing with your
ethernet-dac-project?

Firewire:
Perhaps I should try FW under Linux. I could start on the cheap side. There is quite a nice FW interface from Mackie. Onyx. It's sold for approx. 150€ all over the place. For original 400-500$ it was said to be a real bargain. Parameters are not super high-end.
The good thing though, It'll most probably run under Linux. With the Mackie you'd have a nice multichannel interface.

An alternative could be a Terratec Phase X24 FW.

Both of them seems to have real nice MIC pre-amps.

Good to see that my 48kHz story makes somewhat sense to
somebody. I need to try it again with my Ecdesigns reclocker.
Unfortunately it's not that easy to change the frequency with this module.

Could you shed a bit more light on the frequency sinx/x story.

If that's what you're saying is a case, we're back to the question, what's the less of two evils: A slightly shifted frequency response or heavy jitter?

Cheers

[SunRa]

Hello,

I've tried moc and it is indeed a bit spartan from a visual point of view . I couldn't point out differences between moc and audacious however I don't have a high resolution sistem. It's like puting a V8 on a bike.

I am trying to learn FPGA and general dsp coding in the hope I'll be able to put together something in the line with what peufeu is doing. With a proper digital crossover I'll maybe finish my speakers. (It seems really weird to buy high quality passive crossover components costing as much as DIY'ing an amplifier)

Soundcheck, when do you estimate putting together the updated wiki page?

[soundcheck]

Wiki will be up-to-date as soon as Hardy Studio is released.
Ubuntu Hardy is scheduled for 24th of April.

I'll do a from scratch installation to verify if everything works.

Cheers

[peufeu]

Originally posted by soundcheck

@ peufeu

Good to see you over here again. How are you doing with your
ethernet-dac-project?

Good to see that my 48kHz story makes somewhat sense to
somebody. I need to try it again with my Ecdesigns reclocker.
Unfortunately it's not that easy to change the frequency with this module.

Could you shed a bit more light on the frequency sinx/x story.

If that's what you're saying is a case, we're back to the question, what's the less of two evils: A slightly shifted frequency response or heavy jitter?

Cheers

DigiKey shipped the parts yesterday so finally there is going to be some action, lol.

And, you are using a DDDac, right ? This is non-oversampling if I remember.

So, with any sample & hold DAC, which means any actual DAC, the frequency response of the thing is sin(x)/x with x = 2Pi F/Fs, with Fs the sample frequency. So, at F = Fs/2, frequency response is 0.

This is why non-oversampling DACs have a bad high-frequency response (lots of rolloff at high freqs), see the curve :



Oversampling avoids this by shifting the sampling frequency of the DAC very high so the audible part of the spectrum ends up on the flat top part of the curve.

And I plotted the 44.1k (red), 48k (green), 88.2 (blue), 176.4 (cyan) sampling frequencies. As you can see there will be a small difference in the high frequency response between 44.1k and 48k, about 1-1.5 dB between 10K and 15K. So, it is natural that it sounds differently, just like using a different pair of tweeters. You are having no hallucinations

(Note that I did not include the response of the oversampling filter which normally limits the bandwidth to 20k, this is just the response of the DAC, you can multiply that with the response of the oversampling filter of your choice, which is usually, but not always, a brick wall filter).

Switching to 88.2K sample frequency or more (with SRC in the computer) would also sound different, probably much more different and not subtle at all.

[ssmith]

Originally posted by soundcheck
Wiki will be up-to-date as soon as Hardy Studio is released.
Ubuntu Hardy is scheduled for 24th of April.

I'll do a from scratch installation to verify if everything works.

Cheers

great, look forward to it

[anbello]

@ peufeu

maybe i'am wrong but i remember that the envelope of the response with sin(x)/x is with x = Pi*F/Fs and so we have 0 at Fs and near -3db at Fs/2 for NOS DAC.

ciao
andrea

[peufeu]

Come on, have some respect for the old man Nyquist

Nope, a DAC working at Fs (44100 Hz) is not capable of reproducing Fs/2 (22050 Hz), the zero is at Fs/2.

Everything above Fs/2 is aliasing crap.

[anbello]

@ peufeu

Maximum respect for Nyquist

A sampled system with Fs can reconstruct signal only with F < Fs/2 above this we have aliasing. A NOS DAC is a zero-order hold system and for this sin(x)/x is the envelope of the frequency responce (not the freq. resp. itself) with x = Pi*F/Fs.
This can be seen also experimentally measuring the freq. resp. of a NOS DAC with Fs=44100 obtaining near -3db at 20KHz.

ciao
andrea

[soundcheck]

Hi folks.

Interesting read about SRC:

http://www.mega-nerd.com/erikd/Blog/.../progress.html

http://www.mega-nerd.com/erikd/Blog/...c_compare.html

This has been updated recently:

http://src.infinitewave.ca/


Cheers

[soundcheck]

Hi folks.

To follow up on the last post:

As you might have seen by following above links, the Secret Rabbit Code SRC in version 1.3. is performing much better then before.
I thought it's worth to tell the less experienced folks over here how to get it installed via sources.

Below a brief HowTo about updating libsamplerate.
libsamplerate is used by quite some applications and can affect the soundquality heavily . Unfortunately the Ubuntu guys don't really keep it up2date. My Ubuntu-Studio still had 0.1.1 installed.

Below "Quick and Dirty" instructions assuming that you had it running before, so check with:

$ ls -l /usr/lib | grep libsample

if it's there.

You'll get an output showing beside other lines :

/usr/lib/libsamplerate.so.0.1.1


Now we start:

Download the tar.gz file from here:

http://www.mega-nerd.com/SRC/download.html

$ cd <downloaddir>
$ sudo cp libsamplerate-0.1.3.tar.gz /usr/src
$ cd /usr/src
$ sudo tar xvvf libsamp*gz
$ cd libsample*

Below steps must run error-free so please check the outputs

$ sudo ./configure --prefix /usr
$ sudo make
$ sudo make install

Check:

$ ls -l /usr/lib | grep libsample

should now output:

-rw-r--r-- 1 root root 1517714 2008-04-18 18:31 /usr/lib/libsamplerate.a
-rwxr-xr-x 1 root root 855 2008-04-18 18:31 /usr/lib/libsamplerate.la
lrwxrwxrwx 1 root root 22 2008-04-18 18:31 /usr/lib/libsamplerate.so -> libsamplerate.so.0.1.3
lrwxrwxrwx 1 root root 22 2008-04-18 18:31 /usr/lib/libsamplerate.so.0 -> libsamplerate.so.0.1.3
-rw-r--r-- 1 root root 112196 2007-05-24 14:49 /usr/lib/libsamplerate.so.0.1.1
-rwxr-xr-x 1 root root 1505875 2008-04-18 18:31 /usr/lib/libsamplerate.so.0.1.3


You can see that the .so is now linked to the new 0.1.3 version the old 0.1.1 is sitting idle

if you type:

$sndfile-resample

it'll print out that it uses the 0.1.3. version

Good luck.

Cheers