Raspberry Pi as a USB audio capture device

The Raspberry Pi’s hardware and software support has come a long way in the few months it has been in the wild. I first tried this application in the summer, and the results were dismal. Now, thanks much improved USB driver support under Raspbian, I’m pleased to say it works flawlessly.

Earlier this year, I bought a turntable (ack!) for transferring vinyl to mp3. I have a TC-772 USB phono preamp, which spits out a 48 kHz stereo audio stream. If you plug the USB output of the preamp into a Rapberry Pi (running Raspbian Wheezy with all the updates), it’s instantly recognized as an audio device:

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. 
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. 
Bus 001 Device 004: ID 08bb:2902 Texas Instruments Japan PCM2902 Audio Codec

If you install the ALSA recording utilities (sudo apt-get install alsa-utils pulseaudio – this should pull in a whole bunch of necessary packages), you can record directly from this device with the following command:

arecord -D 'pulse' -V stereo -c 2 -f dat -d 900 out.wav

which records from the ‘pulse’ audio device, displaying a stereo text VU meter (handy for setting levels), writing to a two channel 16-bit 48 kHz file called ‘out.wav’ for a maximum of 900 seconds (15 minutes). arecord has a baffling number of recording source options; arecord -L will show them. ‘pulse’ was the first one I tried.

So how does it sound? Here’s a 30 second excerpt from the only single I owned for years, The Music Tapes‘ “The Television Tells Us/Freeing Song by Reindeer”: Freeing Song by Reindeer – excerpt [mp3]. I’ve saved an even smaller snippet as lossless FLAC so you can see that the waveform’s pretty clean: FreeingSongbyReindeer-tiny_excerpt [flac].

Sounds pretty good. Not quite as good as having Julian play it in your house, I’ll allow, but not bad for a first try with a $35 computer.

6 thoughts on “Raspberry Pi as a USB audio capture device”

  1. Have you tried live playback? Either through the audio jack or streaming over the network?

  2. WI get a similar USB audio device recognized as you do. but ,where did you get the ‘pulse’?When I do arecord -L , All I see is a list of usb audio types, like default and and cant find out how to select my device.

  3. I was hoping to use this to record audio for a short film I’m making. do you think this is the best way to make an audio recording device?

  4. It’ll undoubtedly work to capture audio , but whether it’s the best depends on what your needs and resources are.

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