5 ms·

Raspberry Pi gets its own sound card

48 points by neya 13y ago

bananas 13y ago
I love the fact that a whole ecosystem has appeared around patching up the holes in the Pi's architecture[1]. Unfortunately by the time you've purchased them all, you probably could have bought a BeagleBoard instead. [1] The built in codec and filtering is absolutely horrible making it pretty useless for audio applications.
- beagle3 13y ago
  I have a beaglebone black, but I can't get it to encode FullHD video in realtime. Am I missing something? or is there actually a justification for both the RasPi and the BeagleBone?
  - gardarh 13y ago
    The raspi has a hardware video decoder for some codecs (e.g. H.264) whereas the bbb doesn't. Hence the bbb is not very practical for htpc setup.
- throwawayaway 13y ago
  usually when people do [1] or something like that it's to a link. to my ear the audio out of the pi's hdmi port is perfectly fine. i think the DAC used in the RCA jack is probably not very good. I would pay for a HDMI audio to DAC adapter rather than $33 for another soundcard that just works with the pi.
  - nitrogen 13y ago
    Are there any sub-$100 HDMI DACs that do 5.1 or 7.1? That would be amazingly useful if so.
    - rasz_pl 13y ago
      yes, check ebay http://www.ebay.com/itm/AC3-HDMI-Dolby-HDCD-5-1-2-1-96KHz-24Bit-Digital-Audio-Decoder-Home-Theater-/190974716250?pt=US_Cable_TV_Boxes&hash=item2c76fae95a http://www.ebay.com/itm/AC3-HDMI-Dolby-HDCD-5-1-2-1-96KHz-24... almost every HDMI decoder chip has 4x I2S outputs and just spits out digital audio for example ADV7604 Cheap chinese HDMI-2-VGA adapters use chinese made hdmi receivers, those lack proper i2s outputs and provide only 2 channel SPDIF. example: http://www.taker.im/up/138624609420664378890.jpg http://www.taker.im/up/138624609420664378890.jpg http://lontiumsemi.com/English/ProductShow.asp?ProductId=4 http://lontiumsemi.com/English/ProductShow.asp?ProductId=4
  - jrabone 13y ago
    usually when people do [1] or something like that it's to a link Offtopic, but footnotes predate the web by quite some time. If only we had a easy way of formatting super/subscript...
    - arm 13y ago
      No need for formatting; you can easily get superscripts and subscripts in plain text. See Unicode’s Superscripts and Subscripts Block¹. ―――――― ¹ — https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
  - asb 13y ago
    Audio via HDMI is digital so there really are no problems there. The 3.5mm audio jack is just a simple PWM (see plots at http://www.crazy-audio.com/2013/11/quality-of-the-raspberry-pi-onboard-sound/ http://www.crazy-audio.com/2013/11/quality-of-the-raspberry-...). Sound quality is actually quite improved upon the first release, but it's never going to be great.
- the_ancient 13y ago
  If you using it for HTPC then beagleboard is useless as it has no hardware based video decoding. That is why the Pi is so popular for HTPC's, built in H264 decoding hardware
  - makomk 13y ago
    The Beagleboard's probably a bad example in this case, but I've got a Cubieboard with hardware video decode and line-in/line-out that cost me less than the Pi + this board. (I believe it also has SPDIF on one of the pin headers. All of this was essentially free - the SoC it uses has built-in audio DAC/ADC, Ethernet controller, SATA, and a bunch of other neat stuff.) Plus a lot of early Pi purchasers won't be able to use this without buying another Pi, since the original version doesn't expose the I2S interface required by this.
VexXtreme 13y ago
Nice. PI's built in audio processing is extremely crappy and the analog 3.5mm output is almost unusable for music.
- jablan 13y ago
  How can I actually hear this? I am no audiophile, but I can't notice any audio problems with my Pi.
  - throwawayaway 13y ago
    apparently the DAC for the RCA out is 11bit - but I can't really find any definitive proof of that.
    - jrabone 13y ago
      That should be pretty easy to demonstrate by feeding the output back into a decent 16-bit soundcard - the noise floor should reveal any dithering going on (and if there's no dithering it will be painfully obvious that there's only 2048 discrete output values...) I might have a go tonight.
      - throwawayaway 13y ago
        http://www.raspberrypi.org/phpBB3/viewtopic.php?p=103330 http://www.raspberrypi.org/phpBB3/viewtopic.php?p=103330 Might be of interest to you.
    - jablan 13y ago
      RCA? Isn't the RCA output for video only? I was referring to 3.5mm green audio output.
      - throwawayaway 13y ago
        right you are - that's what I meant.
  - 13y ago
ctz 13y ago
Link: http://uk.farnell.com/wolfson-microelectronics/wolfson-audio-card/audio-card-for-use-with-raspberry/dp/2347264 http://uk.farnell.com/wolfson-microelectronics/wolfson-audio... It's disappointing that this doesn't support v1.0 boards. I hadn't realised that RPis had been fragmented like that.
- omh 13y ago
  It looks like the P5 header that it uses was only added in rev2, and "intended to be a suitable attachment point for ... audio codec boards"[1]. It's definitely a shame that things are fragmented, I was considering adding audio to my old Pi. But at least they're cheap enough to justify buying a second one :-) [1] http://www.raspberrypi.org/archives/1929 http://www.raspberrypi.org/archives/1929
nitrogen 13y ago
What bus is used to communicate with the sound card? The obvious candidate is USB, but the Pi's USB bandwidth is limited and I don't recall whether USB is available on the pin headers.
- miahi 13y ago
  If it uses the P5 header, then it's I2C - so there are no USB issues. I remember reading about (other?) Wolfson DACs on Raspi and they were using I2C.
  - asb 13y ago
    It's actually I2S primarily. I2C would be used for control (volume etc I suppose)
- lxa2 13y ago
  there is no USB on the pin headers, unfortunately (Schematic: http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspbe...)
DiabloD3 13y ago
Raspberry Pi has USB right? So why not just get a Schiit Modi? A very high quality DAC that can be entirely USB powered.
- TkTech 13y ago
  The USB on the Pi has some issues. A lot of devices need to use an external, powered USB hub because the board can't supply enough. Your ethernet is also going through the USB hub.
  - yetihehe 13y ago
    The issue with usb on rpi is that it's unstable. It can drop messages. For ethernet it doesn't mean much, because packets will be retransmitted, but for audio it means sound will occasionally stop for a moment. It's very annoing.
- pretz 13y ago
  The Schiit Modi is double the cost of the Wolfson card and has no audio input capabilities. Seems like for uses outside of an HTPC the Wolfson card provides a lot more flexibility.

48 points by neya 13y ago

I love the fact that a whole ecosystem has appeared around patching up the holes in the Pi's architecture[1]. Unfortunately by the time you've purchased them all, you probably could have bought a BeagleBoard instead. [1] The built in codec and filtering is absolutely horrible making it pretty useless for audio applications.

beagle3 13y ago
I have a beaglebone black, but I can't get it to encode FullHD video in realtime. Am I missing something? or is there actually a justification for both the RasPi and the BeagleBone?
- gardarh 13y ago
  The raspi has a hardware video decoder for some codecs (e.g. H.264) whereas the bbb doesn't. Hence the bbb is not very practical for htpc setup.
throwawayaway 13y ago
usually when people do [1] or something like that it's to a link. to my ear the audio out of the pi's hdmi port is perfectly fine. i think the DAC used in the RCA jack is probably not very good. I would pay for a HDMI audio to DAC adapter rather than $33 for another soundcard that just works with the pi.
- nitrogen 13y ago
  Are there any sub-$100 HDMI DACs that do 5.1 or 7.1? That would be amazingly useful if so.
  - rasz_pl 13y ago
    yes, check ebay http://www.ebay.com/itm/AC3-HDMI-Dolby-HDCD-5-1-2-1-96KHz-24Bit-Digital-Audio-Decoder-Home-Theater-/190974716250?pt=US_Cable_TV_Boxes&hash=item2c76fae95a http://www.ebay.com/itm/AC3-HDMI-Dolby-HDCD-5-1-2-1-96KHz-24... almost every HDMI decoder chip has 4x I2S outputs and just spits out digital audio for example ADV7604 Cheap chinese HDMI-2-VGA adapters use chinese made hdmi receivers, those lack proper i2s outputs and provide only 2 channel SPDIF. example: http://www.taker.im/up/138624609420664378890.jpg http://www.taker.im/up/138624609420664378890.jpg http://lontiumsemi.com/English/ProductShow.asp?ProductId=4 http://lontiumsemi.com/English/ProductShow.asp?ProductId=4
- jrabone 13y ago
  usually when people do [1] or something like that it's to a link Offtopic, but footnotes predate the web by quite some time. If only we had a easy way of formatting super/subscript...
  - arm 13y ago
    No need for formatting; you can easily get superscripts and subscripts in plain text. See Unicode’s Superscripts and Subscripts Block¹. ―――――― ¹ — https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
- asb 13y ago
  Audio via HDMI is digital so there really are no problems there. The 3.5mm audio jack is just a simple PWM (see plots at http://www.crazy-audio.com/2013/11/quality-of-the-raspberry-pi-onboard-sound/ http://www.crazy-audio.com/2013/11/quality-of-the-raspberry-...). Sound quality is actually quite improved upon the first release, but it's never going to be great.
the_ancient 13y ago
If you using it for HTPC then beagleboard is useless as it has no hardware based video decoding. That is why the Pi is so popular for HTPC's, built in H264 decoding hardware
- makomk 13y ago
  The Beagleboard's probably a bad example in this case, but I've got a Cubieboard with hardware video decode and line-in/line-out that cost me less than the Pi + this board. (I believe it also has SPDIF on one of the pin headers. All of this was essentially free - the SoC it uses has built-in audio DAC/ADC, Ethernet controller, SATA, and a bunch of other neat stuff.) Plus a lot of early Pi purchasers won't be able to use this without buying another Pi, since the original version doesn't expose the I2S interface required by this.

VexXtreme 13y ago

Nice. PI's built in audio processing is extremely crappy and the analog 3.5mm output is almost unusable for music.

jablan 13y ago
How can I actually hear this? I am no audiophile, but I can't notice any audio problems with my Pi.
- throwawayaway 13y ago
  apparently the DAC for the RCA out is 11bit - but I can't really find any definitive proof of that.
  - jrabone 13y ago
    That should be pretty easy to demonstrate by feeding the output back into a decent 16-bit soundcard - the noise floor should reveal any dithering going on (and if there's no dithering it will be painfully obvious that there's only 2048 discrete output values...) I might have a go tonight.
    - throwawayaway 13y ago
      http://www.raspberrypi.org/phpBB3/viewtopic.php?p=103330 http://www.raspberrypi.org/phpBB3/viewtopic.php?p=103330 Might be of interest to you.
  - jablan 13y ago
    RCA? Isn't the RCA output for video only? I was referring to 3.5mm green audio output.
    - throwawayaway 13y ago
      right you are - that's what I meant.
- 13y ago

ctz 13y ago

Link: http://uk.farnell.com/wolfson-microelectronics/wolfson-audio-card/audio-card-for-use-with-raspberry/dp/2347264 http://uk.farnell.com/wolfson-microelectronics/wolfson-audio... It's disappointing that this doesn't support v1.0 boards. I hadn't realised that RPis had been fragmented like that.

omh 13y ago
It looks like the P5 header that it uses was only added in rev2, and "intended to be a suitable attachment point for ... audio codec boards"[1]. It's definitely a shame that things are fragmented, I was considering adding audio to my old Pi. But at least they're cheap enough to justify buying a second one :-) [1] http://www.raspberrypi.org/archives/1929 http://www.raspberrypi.org/archives/1929

nitrogen 13y ago

What bus is used to communicate with the sound card? The obvious candidate is USB, but the Pi's USB bandwidth is limited and I don't recall whether USB is available on the pin headers.

miahi 13y ago
If it uses the P5 header, then it's I2C - so there are no USB issues. I remember reading about (other?) Wolfson DACs on Raspi and they were using I2C.
- asb 13y ago
  It's actually I2S primarily. I2C would be used for control (volume etc I suppose)
lxa2 13y ago
there is no USB on the pin headers, unfortunately (Schematic: http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspbe...)

DiabloD3 13y ago

Raspberry Pi has USB right? So why not just get a Schiit Modi? A very high quality DAC that can be entirely USB powered.

TkTech 13y ago
The USB on the Pi has some issues. A lot of devices need to use an external, powered USB hub because the board can't supply enough. Your ethernet is also going through the USB hub.
- yetihehe 13y ago
  The issue with usb on rpi is that it's unstable. It can drop messages. For ethernet it doesn't mean much, because packets will be retransmitted, but for audio it means sound will occasionally stop for a moment. It's very annoing.
pretz 13y ago
The Schiit Modi is double the cost of the Wolfson card and has no audio input capabilities. Seems like for uses outside of an HTPC the Wolfson card provides a lot more flexibility.