USB soundcard...Finally good (non HDMI) Analog Audio

[ski522]

Well...took a bit of work, but I finally have decent sound out of my el-cheapo USB card. I couldn't take the popping between songs with the onboard analog port any more. So I bought a cheap CM802 based USB card. The one I got was Meritline http://www.meritline.com/usb-sound-adap ... 60824.aspx.

The PI reconginzed the card right away, but I was getting static playing songs or using Pianobar (Pandora shell app). So I did a few steps to fix it

1) Demoted the onboard card to the second device by

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sudo nano/etc/modprobe.d/alsa-base.conf 
Made the following entries in the file
#options snd-usb-audio index=-2
options snd_bcm2835=-2

exit
reboot

2) Then I had to add the following to the /boot/cmdline.txt

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dwc_otg.speed=1

3) Created ~/.libao file in my home directory and entered the following:

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driver=alsa
dev=default

4) Lastly created a ~/.asoundrc in my home directory and entered the following:

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pcm.!default {
              type asym
              playback.pcm "defaultplayback"
              capture.pcm "defaultrec"
                hint{   show on
                   description "default play and rec koko"
                }
      }

      pcm.defaultrec {
              type plug
              slave {
                  pcm "hw:0,0"
                  rate 48000 
                  channels 2
                  format S16_LE
              }
                hint{   show on
                   description "default rec koko"
                }

      }

  pcm.defaultplayback{
          type rate
          slave.pcm mix1
          slave.rate 48000 

          #Intel(R) Core(TM)2 Duo CPU     E7500  @ 2.93GHz:

            #converter "samplerate_best"     # perfect: 16%cpu, maybe overkill
            #converter "samplerate_medium"   # almost perfect: 6%cpu
            #converter "samplerate"          # good: 4%cpu, definitely usable
            #converter "samplerate_linear"   # bad: 2%cpu, way better than default wine resampler
            #converter "samplerate_order"    # very bad: 2%cpu, like the default wine resampler

          converter "samplerate"

            hint{   show on
                   description "default play koko"
            }
  }

    pcm.mix1 {
            type dmix
            ipc_key 1024
            slave {
                pcm "hw:0,0"
                rate 48000
                periods 128
                period_time 0
                period_size 1024 # must be power of 2
                buffer_size 65536

            }
    }

Perfect sound and can now listen to pianobar from my PI and place all my CD's I ripped in FLAC. My next step will be tackling XBMC which requires some hacks from what I see in this post http://forum.stmlabs.com/showthread.php?tid=1052.

Slowly my PI is becoming a mini-media center I was looking for.

[Argon]

So, with this USB soundcard, no pops and no noise !?
I use Squeezeplug in the bathroom with the 3.5 audio out and I get always a lot of background noise when I play something...

[ski522]

Nope...none of that, no popping between songs, no static in music either once I got the configuration figured out.

BTW minor typo in my setting above

options snd_bcm2835 index=-2

forgot "index" in my original post.

[redhawk]

I have what looks like an identical USB dongle except it's black and based on the CM108 chipset.

Did you have any luck getting the buttons to work the volume control??

Richard S.

[ski522]

Yes, I beleive that are exactly the same (other than color), fairly certain mine has the CM108 as well. As for the volume controls, I don't need to use them since I'm connected to my home stereo, but just did a quick test and they don't seem to work. I set up my volume initially using alsamixer.

[Argon]

Alright, I purchased also one. Now 3 / 4 weeks waiting untill it arrieves...

[ski522]

Okay, while the sound is vastly better than the on board sound, still not a 100%...maybe 95% happy. Decided now the best thing to do is just run digital to my home receiver and let it's DAC handle the conversion. So just threw down $14 to buy this guy http://www.aliexpress.com/store/product ... o_detail_a which should work with the PI.


What is nice about this card is that it has TOS and Coax ports...should have it in 2 weeks.

On a different note, it seems that the PI's USB interface has serious problems, since adding the sound card I'm seeing a lot of issue with the PI dropping network connection. More can be found at this thread http://www.raspberrypi.org/phpBB3/viewt ... b+elephant. I had to put in a script to automatically reboot the PI every time it loses network connectivity...seeing this message constantly in the log

smsc95xx 1-1.1:1.0: eth0: Failed to write register index 0x00000014

I admit I'm getting to the point of wishing I hadn't bought the PI and just got a Roku XD...my cost would have be less now at this point! But I have the PI so I'm going to see if I can make this thing a good audio media player while hoping not to throw much more money at it!

[Fixnode]

Hey

I ordered the same sound card that you have, it will arrive in the next few days. I wanted to ask if you found a reliable way to get good sound in XBMC? I want to use this solution for a Car-PC project and wanted to know if this sound card is good with XBMC sound drivers

Let me know,
Phillip K

[ski522]

You need to follow this thread to get XBMC to work with external sound cards
http://forum.stmlabs.com/showthread.php?tid=1052

[computaholic]

For those who care about HiFi Performance: http://www.thomann.de/de/behringer_ucontrol_uca_202.htm

[RaTTuS]

For those who care about HiFi Performance: ...

Use the HDMI device as it was intended ;-p

[ski522]

For those who care about HiFi Performance: ...

Use the HDMI device as it was intended ;-p

I would if it wasn't hooked up to my TV...I don't want to have to turn on my 100W TV everytime I want listen to Pandora via my stereo receiver...kind of defeats the whole concept of a low powered device.

[ski522]

For those who care about HiFi Performance: http://www.thomann.de/de/behringer_ucontrol_uca_202.htm

Moot point if I'm planning on using the SPDIF/TOS connection and let my receiver, which has a high quality DAC, do the conversion. That card would would do the job if I wanted to run analog signals to my stereo instead.

[speculatrix]

That looks like quite a fat USB device. Does it block the other USB port?

And do you think it would be possible to drive a small 8ohm or 4ohm speaker directly from the headphone jack?

[redhawk]

Most audio dongles are too chubby and would obstruct the other USB port so a cable extender is certainly a requirement.
As for audio output they're nice and loud for headphones but not so for speakers due to their lower impedance however still better than the PI on-board crap.

Richard S.

[speculatrix]

Thanks for the info. Probably not going to work for me, then.

I'm building a 'dawn clock' - actually an upgrade of a current one based on an Arduino and wave shield. I need to be able to play MP3s programmatically. I tried amplifying the headphone output with one of these mono amps, but it doesn't work (don't know why). No output at all (although I've checked the amp works with other sources). My needs are simple - mono will do. I just want to get the Pi's audio output to a small 8ohm speaker. Why should that be so hard?

[ski522]

Okay got my new board in and it works great! Actually shipping from China wasn't so bad...ordered the Oct 29th, received it yesterday Nov 10th.



No problems when testing SPDIF via the the coax and TOS connections. The sound quality is excellent and I can't tell the difference from my main HTPC which has a more expensive sound card...that horrendous popping noise you get on the Pi's analog output between songs is gone now running this board's SPDIF connections ! I haven't tested the analog connection on the board, not something I actually need to use.

The only problem I have is dealing with the USB elephant issue (see post http://www.raspberrypi.org/phpBB3/viewt ... t=elephant) to see what I'm talking about.

The USB issue rears its ugly head when I try to run CPU intensive apps like XBMC. Pianobar (Pandora Client) and playing rip FLAC CD's via mplayer doesn't cause problems. I hope they get the USB issues resolved soon, the PI will then make a pretty decent media server!

So anyone looking for great sound digitally and can't use the HDMI connection can't go wrong with this card, especially for $14! Next step is to figure out good way to mount it and/or find a small case to fit the card in.

[zbicin]

@ski522

Can you test the analog output, please? I'm really interested in the result

[Argon]

+1 !

[Metatronin]

I couldn't take the popping between songs with the onboard analog port any more.

You can get rid of this by matching the impediance between the rpi and your stereo receiver, that is if the receiver doesn't have this built in already. Usually takes a capacitor and resistor to ground, per channel. The Pi seems not to have any active impedance matching or any type of amplification.

[ski522]

@ski522

Can you test the analog output, please? I'm really interested in the result

Okay, took a few minutes to test the analog port...this card is a winner! The sound is excellent out of the analog port, almost as good at the digital PCM out of the SPDIF connection. It was actually so good that I thought my stereo was masking/improving the analog output, so I plugged in a decent pair of headphones into the card to make sure and music through the headphones was excellent as well! Can't hear any background hiss during quiet moments in songs and no popping at all between songs...everything from ripped FLAC to Pandora sounded great!

The DAC on this board is based on TI's PCM2704 which seems to get decent reviews in general. More info on the chip can be found http://www.ti.com/product/pcm2704c.

As a side note, the dimensions for the card are wrong on the web link I provided, it's actually smaller than what's listed being 5.4cm x 5cm (L x W), next step is finding a decent way of mounting or enclosing the board.

[ski522]

I couldn't take the popping between songs with the onboard analog port any more.

You can get rid of this by matching the impediance between the rpi and your stereo receiver, that is if the receiver doesn't have this built in already. Usually takes a capacitor and resistor to ground, per channel. The Pi seems not to have any active impedance matching or any type of amplification.

I believe the problem occurs within the audio driver itself when it initializes/de-initializes between songs and not so much a impedance problem IMHO. I actually found a way around the popping for the onboard analog port by install pulseaudio. Pulseaudio keeps the sound driver active all the times so the popping between songs disappears. The only thing I didn't like about pulse was that there was about 300ms delay between the start of a playing a song to actually hearing the music.

At the end of the day, I'd rather let my stereo do the conversion to analog using it's DAC, so the $14 I spent on this board was well worth it!

[Argon]

Is the front of the dac a normal usb connector? I don't see this on the picture.

[ski522]

Is the front of the dac a normal usb connector? I don't see this on the picture.

No, it's a type B adaptor. The link I provided on the DAC shows additional pics.



Also for new readers, my original post was regarding an el-cheapo card that plugged into the USB port of the PI. It was okay, but I didn't really like the card and my last few post are regarding this card I got at http://www.aliexpress.com/store/product ... o_detail_a

[Metatronin]

Wierd. Why would the sound not always be on? I'm just asking because I have never had this problem as of yet. Maybe my stereo is masking it with some type of "electrical thump" protection on the inputs? I don't hear it through my DIY headphone amp either.