[Toe Tag]

When I plug my Nexus 7, running USB Audio Player Pro (UAPP), into my ODAC, then onward to my Tralucent T1, it works great.
 
But when I plug the Nexus 7 (same cable) (mini-USB on end, into my hub, and then the hub into the ODAC, I get no music. UAPP seems to recognize that there is a DAC downstream. But actually I get like a 200 Hz (plus or minus) tone, and no music. Even if I unplug the power to the hub. And regardless of whether I plug the Nexus into the hub. 
 
I am just trying to inject some power into the devices, am I doing something fundamentally wrong?
 
EDIT: OK I got it partly working. If I only plug one downstream device (ODAC, or DACport LX) into the hub, its fine. But if I plug in a second device (e.g. the Tralucent, to power or charge it), no sound. Maybe this is an issue with UAPP, I will ask the author, who is present on head-fi. 
 
One question though, the Nexus 7 is not getting a charge back from the hub, do I need to do something special for this? It is just a USB OTG cable, to USB female, then a USB male to USB mini into the DAC. 

 

[Davy Wentzler]

  When I plug my Nexus 7, running USB Audio Player Pro (UAPP), into my ODAC, then onward to my Tralucent T1, it works great.
 
But when I plug the Nexus 7 (same cable) (mini-USB on end, into my hub, and then the hub into the ODAC, I get no music. UAPP seems to recognize that there is a DAC downstream. But actually I get like a 200 Hz (plus or minus) tone, and no music. Even if I unplug the power to the hub. And regardless of whether I plug the Nexus into the hub. 
 
I am just trying to inject some power into the devices, am I doing something fundamentally wrong?
 
EDIT: OK I got it partly working. If I only plug one downstream device (ODAC, or DACport LX) into the hub, its fine. But if I plug in a second device (e.g. the Tralucent, to power or charge it), no sound. Maybe this is an issue with UAPP, I will ask the author, who is present on head-fi. 
 
One question though, the Nexus 7 is not getting a charge back from the hub, do I need to do something special for this? It is just a USB OTG cable, to USB female, then a USB male to USB mini into the DAC. 

 
To be honest, we haven't really tested how our apps behave when plugging in multiple audio devices, although we have done tests with a combination of DAC and USB stick plugged into a hub. Anyway, at the moment, the answer is indeed as you already found out: 'please do not do that for the time being'.
 
There are some contradicting experiences of people using a USB OTG-Y cable, like this:

 
some say it charges their device too, some say it doesn't.

 

[Toe Tag]

OK the Nexus 7 is charging now so really I only have 1 problem, and it sounds like its known and understood to be part of UAPP, and may even get fixed some day. Probably not the most urgent matter but yes, it sounds like you can only support 1 downstream device (the DAC) when using a hub with UAPP. So what I'll do is, move cable that goes downstream from the hub, move it to the amp when it needs charging. Then move the cable back to the DAC once its charged and listen to music again. Probably better for the amp to be running off its battery than have a noisy PSU in the mix anyway. 
 
To summarize, the bug is minor, yet easy to reproduce. 1. use a hub 2. plug a second downstream device into the hub. (FWIW my second downstream device is a Tralucent T1 amp.) Now what is strange is, that this amp is only using the USB to recharge itself, so I wonder what business it has injecting itself into any USB data protocol conversations. Maybe I could get a special USB cable that has the data lines cut. Or use my workaround above. Or feed the amp juice from a different USB power supply. Note that I use the hub because the DACport LX, even though it has no amp and is just a DAC, sucks down power like a space heater.