Raspberry Pi & DIY
Jan 12, 2013 at 2:54 AM Post #62 of 65
I tried both of my DACs with and without a powered hub and it made no difference to the noise. In its current state, I feel that the Pi doesn't seem suitable as an audio solution unfortunately. It's always possible that this issue could be debugged and fixed by someone in the Linux community in future.
 
Jan 12, 2013 at 3:22 AM Post #63 of 65
I did have a quick search of the thread and didn't see any mention of this, but did anybody try setting their USB speed to 1.1? I recall reading about it a little while ago and a fair number of people said it gave them crystal sound when they did (it does however kill the ethernet speed). I believe that this issue is supposed to be fixed on the revision c boards too.
 
Cheers
 
Jan 15, 2013 at 4:57 PM Post #65 of 65
Hello,
  I've been reading the thread while I choose a DAC that's a little more up market and difficult to drive because it will be 24bit/192khz.  I have two Raspberry Pis running without any extra noises.  One is running the SMSL DAC I mentioned earlier and the other is an Aureon 5.1 external soundcard (only for stereo.)  Both are set up the same.  When I first played with a Pi I didn't have a suitable power supply because of this I got the problems mentioned here plus network drop outs etc.  I read that the Pi needs a 2amp power supply.  I bought these from that-auction-site.  Search for 'white 2 amp uk 3-pin micro USB mains charger'.  There is a problem on the original model B's too.  I haven't tried to fix it but here is the detail:
 
http://himeshp.blogspot.se/2012/07/raspberry-pi-usb-power-issues-ultimate.html
 
This is how I set up my Pi.  The early distributions of GNU/Linux for the Pi weren't great for web browsing etc.  I bought one for the kids and one for me to try Squeezeslave on.  I gave up on using the Pi as a GNU/Linux for the kids.  For setting up Squeezeslave you don't need a monitor and keyboard.  I only use those until the point I have SSH running.  It could be that people who are having problems are using their Pis connected through HDMI.  From SSH, I disable the on board audio and reboot.  The DAC will be seen as hw1,something.  You can change it so that it the DAC is hw0,something but it's not necessary.
 
I use this:
 
/usr/local/bin/squeezeslave-1.2-381 -v off --mac 00:00:00:00:0a:0b -R 192.168.0.3 --latency 1000
 
from the lnx-armel distribution on:
 
http://sourceforge.net/projects/softsqueeze/files/squeezeslave/
 
Because I've disabled the onboard sound I don't have point the software at the DAC but this:
 
~# /usr/local/bin/squeezeslave-1.2-381 -L
Output devices:
* 0: (ALSA) S.M.S.L  SD-1955+: USB Audio #1 (hw:0,1) (10/42)
 
will list devices.
 
Other things that might make a difference:
 
o I run squeezeslave as root.
o I've played with nrpacks.  Setting to 1 causes noise.  Not setting and setting to 10 gives the same great performance.
 
Maybe I'm lucky.  Maybe my USB cables are super duper audio USB cables (I doubt it).  I would have been very upset if the sound was awful on the DAC, headphone amp and headphones that cost me £500.  It worked first time with the Aureon though.
 
To the person who would like a prescription for perfect audio on the Pi without any investment of time:  I'd rather struggle with this than queue on a Saturday to argue the toss with a spotty 'Genius' at the Apple bar.  This is way cheaper too.
 
I'm going to write up a start-from-scratch recipe when I get my new DAC.  I suspect that the Pi having so much hardware on its USB bus maybe too much if I add 192khz to the mix.  I'll post a link here whether it works or not.
 
[edit] I believe 192khz will need a 3.7.1 Linux kernel for asynchronous USB.
 

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