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Single PC solution - Use of 2 USB sound cards as crossovers using PAX Rack
Single PC solution - Use of 2 USB sound cards as crossovers using PAX Rack
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Old 11th June 2019, 11:20 PM   #51
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by arcgotic View Post
Do you know, in Windows is possible this? Using multiple USB soundcards?
I design usb scopes and LC meters.
Each device has a VID and PID and if two devices have the same ones then they will clash.
There may be a way around it, I am not sure.
Either way the USB devices needs to know which one the data is for.
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Old 12th June 2019, 07:53 AM   #52
phofman is offline phofman  Czech Republic
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Quote:
Originally Posted by nigelwright7557 View Post
Each device has a VID and PID and if two devices have the same ones then they will clash.
VID and PID are info for the USB core driver to load the correct higher-level device driver. The USB core driver uses bus -> port -> dev IDs for identifying the devices:

Code:
hestia@hestia:~$ lsusb -t
/:  Bus 08.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/:  Bus 07.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
    |__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/6p, 480M
    |__ Port 6: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
        |__ Port 4: Dev 3, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
        |__ Port 4: Dev 3, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/6p, 480M
If windows USB driver stack could not distinguish two devices with identical VID/PID, it would be a very bad design. Hooking several identical keyboards/mice/USB hubs etc. would not work.

In linux device names are used while it is possible to assign fixed distinct names to identical devices in different USB ports via those udev rules. Is anything like that available in windows?

Last edited by phofman; 12th June 2019 at 07:57 AM.
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Old 12th June 2019, 11:10 AM   #53
Tfive is offline Tfive  Germany
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Quote:
Originally Posted by Tromperie View Post
Oops, I realised after about 10 minutes after posting. It doesn't show up in the dropdown box.
can you please post the output of "pactl list sinks", preferrably to a pastebin... with the combined soundcard active in pulseaudio of course.
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Old 12th June 2019, 11:20 AM   #54
phofman is offline phofman  Czech Republic
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Please do not forget to run

Code:
pactl load-module module-alsa-sink device="multidev"
first to load the PCM device into pulseaudio. By default PA loads sound cards only, not the additional PCM devices created by alsa configs.
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Old 12th June 2019, 11:28 AM   #55
Tfive is offline Tfive  Germany
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Quote:
Originally Posted by phofman View Post
Please do not forget to run

Code:
pactl load-module module-alsa-sink device="multidev"
first to load the PCM device into pulseaudio. By default PA loads sound cards only, not the additional PCM devices created by alsa configs.
...or put the load-module line into default.pa...
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Old 12th June 2019, 11:52 AM   #56
phofman is offline phofman  Czech Republic
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A minor difference is calling the pactl command directly tells whether loading the device was successful or not. The same problem in config file would have to be identified from PA logs I guess. For testing I would prefer the direct-feedback procedure.

One more thing regarding the GUI - upon loading the sink the new device does not appear in hardware list, but in output selection list. The "pactl list sinks" command lists it too.
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Old 12th June 2019, 11:59 AM   #57
Tfive is offline Tfive  Germany
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I guess output selection means in the config dialog for outputs in PaXoverRack. What do you mean by hardware list?
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Old 12th June 2019, 12:09 PM   #58
phofman is offline phofman  Czech Republic
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My .asoundrc defines virtual balanced inputs/outputs device called symmetric:

Code:
hestia@hestia:~$ pactl load-module module-alsa-sink device="symmetric"
21
Mint Hardware tab = Configuration tab in pavucontrol - the device is not listed there (probably because it requires no configuration). It is listed in Outputs tab in both GUI tools. I have not tried PaXoverRack.
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Old 12th June 2019, 12:10 PM   #59
DACMan1 is offline DACMan1  South Africa
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This should be trivial to achieve with brutefir, but you will never have the exact same timing between the two devices - they will always drift. I cannot imagine getting very good stereo imaging with this sort of setup.
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Old 12th June 2019, 12:40 PM   #60
phofman is offline phofman  Czech Republic
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Why should USB-adaptive soundcards connected to single USB controller drift apart?
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