Dragonfly USB DAC under 9.1-RELEASE
Hans Petter Selasky
hps at bitfrost.no
Sun Apr 21 15:55:51 UTC 2013
On 04/21/13 01:53, Craig Leres wrote:
> Has anybody tried a Dragonfly USB DAC with FreeBSD 9.1-RELEASE? I picked
> up one last week can't quite get it to work
> My streamer is a Barix instreamer. I normally feed it with 48 KHz PCM
> from a Sirius Satellite radio receiver via toslink. I can also feed it
> directly with 44.1 KHz from VBR MP3s downloaded from amazon.com or 48
> KHz RIFF/WAVE files.
> I'm using the multimedia/xmms port with the OSS plugin. I use mpg123 to
> play MP3s. I think it uses OSS too. And obviously ossplay uses OSS.
> The DACs I have previously used are Realtek ALC883 and ALC888's on the
> motherboard of my desktop machines. With the Dragonfly plugged in,
> /dev/sndstat says:
> ice 327 % cat /dev/sndstat
> FreeBSD Audio Driver (newpcm: 64bit 2009061500/amd64)
> Installed devices:
> pcm0: <ATI R6xx (HDMI)> on hdaa0 (1p:1v/0r:0v)
> pcm1: <Realtek ALC883 (Analog 7.1+HP/2.0)> on hdaa1 (1p:2v/2r:1v)
> pcm2: <USB audio> at ? (1p:1v/0r:0v)
> (The Dragonfly is pcm2.)
> The first issue was a pop every 5 seconds. I noticed the LED was magenta
> which indicated the DAC was running at 96K so I looked at
> /sys/dev/sound/usb/uaudio.c and found that thd driver was defaulting to
> the highest sample rate the DAC reports. This meant my 48K input source
> was being upsampled.
> Looking at the driver a bit more I changed:
> sysctl hw.usb.uaudio.default_rate=48000
> and removed/inserted the DAC and that fixes it at 48K (confirmed by a
> blue LED) and the 5 second pops are gone.
> Now I have noticeable audio glitches about ever minute or so. I don't
> think it's source material related. For example, if I play the same
> sound file over and over and note the number of seconds into the song
> when a glitch happens, it rarely happens at the same time.
> I tried to attach a short wav file of an example glitch but got a funny
> bounce ("550 5.7.1 Size too green"?) so I put a copy here:
> Thinking it might be a ground loop problem, I got an Olimex USB-ISO USB
> isolator. It works ok but the glitches are still present.
> The Dragonfly sounds very nice so I hate to send it back; does anyone
> have suggestions for me? I called Audio Quest but the tech I talked to
> admitted he had only been trained for Windows and OSX.
There are multiple options for debugging this issue.
1) Look at the usbdump utility for dumping the data communication for
usbdump -i usbusX -f Y -s 65536
I suspect your device uses rate adaption, and that it does not work
usbconfig -d X.Y dump_curr_config_desc
I use a Fasttracker over USB having eight 24-bit tracks at 96KHz, and
that works just fine. Also all the additional mixer functionality is
supported through extended pcm mixer sysctls.
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