Digital Volume Control - Best Practice

[sonorejr]

**OBSOLETE POST**

Vortexbox Player (and most other MPD clients) allow you to contol volume digitally. When playing back ripped cds in 16/44.1 it's best not to employ digital volume control as you drop 8 bits of data. The solution is to add 8 bits in the first place so nothing is lost when digital volume control is employed. MPD can do this and it's pretty easy to do without much cpu usage. Further upsampling may be cpu intensive. Also, keep in mind that a 16 bit dac may have an issue with this change. The old saying applies…trust, but verify!


If you want to try it out add the following to the mpd configuration file in your output section between { }:


format "*:24:*"
mixer_type "software"


Then add add the following to the mpd configuration file outside of the output section:
samplerate_converter "Best Sinc Interpolator"



sonorejr

[donberryman]

Please pardon my ignorance, but I have two questions:




Where is the mpd configuration file?




Will this work with the Audio Advantage Micro USB Sound Card connected to teh VBA?




Thanks

[sonorejr]

donberryman, do you have the dac up and running? FYI when you have the computer volume sit to max it will send a 24 bit signal to your dac. If you have a 16 bit dac it will not work. So if it works will depends on your dac.




sonorejr

[Ron Olsen]

donberryman said:

Where is the mpd configuration file?



/etc/vortexbox-player/mpd0.conf

[donberryman]

Thanks.


I don't know if my DAC is 16 or 24 bits,, so I'll give it a try when I get home tonight. I assume that since I am sending a digital signal to my reciever, that that is where my DAC resides. S/PDIF is either a 20 or 24bit

[donberryman]

looking /etc/vortexbox-player/mpd0.conf, the contents are:



# Created by VortexBox on February 10, 2010, 4:59 pm
# If you edit this file it will be over written the next time you make changes in the GUI.
#
music_directory "/storage/music/flac"
playlist_directory "/var/lib/mpd/playlists"
db_file "/var/lib/mpd/database"
log_file "/var/log/mpd.log"
pid_file "/var/lib/mpd/pid"
state_file "/var/lib/mpd/state"
sticker_file "/var/lib/mpd/sticker.sql"
port "6600"
zeroconf_enabled "no"





I don't see any 'output section between:{ }'


What is the syntax I need for adding an 'output section'?

[sonorejr]

donberryman, in the web gui click on the second to the last icon (speaker with vortexbox icon) and let me know each name you see and the corresponding audio device. Just the stuff under the green bar!




sonorejr

[donberryman]

sonorejr


name VortexBox Player


mac adress 00:04:00:00:00:01


audio device Default




ALSA device list


0 [default ]: USB-Audio - USB Sound Device
C-Media INC. USB Sound Device at usb-0000:00:1d.0-2, full speed
1 [Intel ]: HDA-Intel - HDA Intel
HDA Intel at 0xfea38000 irq 16


List of audio device ports

2: : timer
3: : sequencer
4: [ 0- 0]: digital audio playback
5: [ 0] : control
6: [ 1- 2]: digital audio capture
7: [ 1- 0]: digital audio playback
8: [ 1- 0]: digital audio capture
9: [ 1- 0]: hardware dependent
10: [ 1] : control

[sonorejr]

donberryman, replace default with hw:0,0 and submit. The open the mpd0.conf file again and it should look like this:



music_directory "/storage/music/flac"
playlist_directory "/var/lib/mpd/playlists"
db_file "/var/lib/mpd/database"
log_file "/var/log/mpd.log"
pid_file "/var/lib/mpd/pid"
state_file "/var/lib/mpd/state"
sticker_file "/var/lib/mpd/sticker.sql"
port "6600″
zeroconf_enabled "no"


audio_output {
type "alsa"
name "vortexbox Player"
device "hw:0,0″
}


modify it to look like this:



music_directory "/storage/music/flac"
playlist_directory "/var/lib/mpd/playlists"
db_file "/var/lib/mpd/database"
log_file "/var/log/mpd.log"
pid_file "/var/lib/mpd/pid"
state_file "/var/lib/mpd/state"
sticker_file "/var/lib/mpd/sticker.sql"
port "6600″
zeroconf_enabled "no"


samplerate_converter "Best Sinc Interpolator"


audio_output {
type "alsa"
name "vortexbox Player"
device "hw:0,0″
format "*:24:*"
mixer_type "software"
}


save the conf file and restart the unit.




sonorejr

[donberryman]

Thanks,




Now I have added the new items and my conf file is



# Created by VortexBox on March 9, 2010, 6:54 pm
# If you edit this file it will be over written the next time you make changes in the GUI.
#
music_directory "/storage/music/flac"
playlist_directory "/var/lib/mpd/playlists"
db_file "/var/lib/mpd/database"
log_file "/var/log/mpd.log"
pid_file "/var/lib/mpd/pid"
state_file "/var/lib/mpd/state"
sticker_file "/var/lib/mpd/sticker.sql"
port "6600"
zeroconf_enabled "no"
samplerate_converter "Best Sinc Interpolator"

audio_output {
type "alsa"
name "VortexBox Player"
device "hw0,0"
mixer_type "software"
format "*:24:*"
mixer_type "software"
}