RPI + 2x USB FDA amps - time synch OK or issue?

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#41
JMF11 said:
Not lucky this time... I have found a small USB hub. Plugged the 2 amps on it. I can play each one individually. But not together.

When I launch the music to the second one, it fails with
Code: 
ERROR:  Connecting chainsetup failed: "Enabling chainsetup: AUDIOIO-ALSA:
... Error when setting up hwparams: Broken pipe"

The USB structure, with the USB hub is:
Code: 
jmf@orangepipc:~/ecasound$ lsusb -t
/:  Bus 08.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ohci/1p, 12M
/:  Bus 07.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ohci/1p, 12M
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ohci/1p, 12M
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ohci/1p, 12M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ehci/1p, 480M
    |__ Port 1: Dev 3, If 0, Class=Hub, Driver=hub/4p, 480M
        |__ Port 2: Dev 5, If 0, Class=Audio, Driver=snd-usb-audio, 12M
        |__ Port 2: Dev 5, If 1, Class=Audio, Driver=snd-usb-audio, 12M
        |__ Port 2: Dev 5, If 2, Class=Human Interface Device, Driver=usbhid, 12M
        |__ Port 3: Dev 4, If 0, Class=Audio, Driver=snd-usb-audio, 12M
        |__ Port 3: Dev 4, If 1, Class=Audio, Driver=snd-usb-audio, 12M
        |__ Port 3: Dev 4, If 2, Class=Human Interface Device, Driver=usbhid, 12M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ehci/1p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ehci/1p, 480M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=sunxi-ehci/1p, 480M

The hub is a 2.0 one, not powered (but the amps should not pull too much current)...

I feel that there is no need to continue to insist in that implementation. It is not a robust design.

JMF
Click to expand...
Wow, that is really unfortunate. I also own an Orange Pi PC and I did do some basic testing of it but nothing very extensive. I did not realize that there were multiple USB busses on board and that two DACs could end up on different busses randomly, and therefore not play back in sync (if I am understanding the problem correctly!).

Perhaps it's time to try a Raspberry Pi 2 or 3?

The OrangePi PC would still work for other uses that either have a multichannel DAC or you just want stereo output from a single DAC.
 
#42
I must say that I had a good experience with the Orange Pi PC with armbian. It worked well out of the box.

However, There must be something wrong with using 2 FX-Audio D802 on the same USB bus, even using USB audio 1.0 "low speed". I had this issue yesterday with a USB hub on the Orange Pi. But I also had the same type of issue in my early prototyping stage on my laptop (http://www.diyaudio.com/forums/pc-b...rtual-multi-channel-device-3.html#post4732180). So not sure at all that it would work on the RPi.

It is not critical as I now think that it is not a good design, but I would be happy to know that is the real issue behind this. May it come from the USB amps ?

I'm disappointed that the USB hub trick does not work...

JMF
 
#43
In general use it does not matter that the USB frame is too small for two configuration packets - what is the chance of initializing two usb soundcards simultaneously within 1ms. Yeah, I would agree that the design requires features above specifications of the underlying technology.
 
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