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TPA - USB Transport

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#88
USB Bus power...

leifchristensen said:
looking fw to hear this
already use batterypowered hiface-s/pdif and sounds pretty good into BII
but
why bus powered(you mean via usb?)?
best
Leif
Norway
Click to expand...

Leif: using USB bus power does not have to be a limitation if the power is handled properly. The Ayre QB-9 (product of the year, sounds incredible, blah, blah) runs its USB receiver off of the USB bus. And I am using a Wavelength Audio Wavelink USB-SPDIF interface into my B-II which runs off of the bus power, and it sounds amazing. The designer just has to make sure that the USB bus power is appropriately filtered, and regulated, and that some kind of isolation is employed between computer and DAC.
In any case, if you are paranoid about the USB bus power, it is a simple matter to break out the power and ground leads from a USB cable and apply the 5 VDC supply of your choice.
 
#90
Jkeny

I am well aware of what you are saying. You can still break out the ground and + from the cable and apply whatever supply you want, the ground reference has to stay intact between the computer and USB receiver, and your new supply just references the same ground. I was not suggesting that applying external power provides any (ground) isolation.
In any case, what Russ White/TPA is working on already isolates the computer from the DAC.
 
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#91
The isolation method I am using has nothing to do with the USB PHY. 🙂

There will be no penalty for being bus powered and everything will be locally regulated. The PCM output need not be coupled to the PC in any way (not even GND).

I received the parts I am using for isolation today, and will be testing them tomorrow.
 
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#92
barrows said:
In any case, if you are paranoid about the USB bus power, it is a simple matter to break out the power and ground leads from a USB cable and apply the 5 VDC supply of your choice.
Click to expand...

It just sounded to me like you were giving Leif advice to cut the power & ground of the USB cable & connect in a 5V DC supply? This can possibly cause damage to the USB device as the differential USB signal has no longer a reference voltage & could damage the USB receiver chip in the USB device connected!
 
#93
Unfortunately, not being bus powered is a bit more involved than just supplying 5V.

In this case, there is nothing to be gained by using external power anyway.

In fact by going bus powered you save quite a lot of trouble, not to mention unnecessary hardware.

The key really is just to have good regulation and bypass.
 
#98
lauret said:
I'm sure I am not the only one curious about linux compatibility of this USB-receiver. Can someone knowledgeable comment on this?
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I just bought the xmos UAC2.0 dev board with the intention of using it under Linux. At least one person here on diya has reported running it without problems so I'm assuming it'll work. Since my understanding so far is that the TP offering will use the same xmos firmware but optimized hardware, this should be a good indication. I'm hoping I'll get around to testing it this weekend.
 
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