separate power supply for USB powered device

joeling39 · 26th November 2004, 01:18 AM

Hi,

I am thinking of adding a separate power supply to a USB powered device. Do I have to connect the ground(i.e. 0V) of the new power supply to the ground of the supply coming from the PC ?

The signal will come from the PC USB port, the power supply from the PC USB port will be severed & replaced with a external power supply. The ground of the new external power supply (the 0V) will be tied to the ground of the USB port supply. Is this OK?

Thanks.

Regards,
Joe Ling

Fin · 26th November 2004, 01:42 AM

Why not use a small powered USB hub?

joeling39 · 26th November 2004, 02:43 AM

Dear Fin,

Thanks for the query. Maybe it's time for me to disclose more :

The USB device in question is a sound card mated to a clock conditioner (Apogee Big Ben). I want a very good quality 5V power supply to the USB sound card.

My guess is that a power USB hub is not much better than the power supply from the PC.

Please assist. Thanks.

Regards,
Joe Ling

Fin · 26th November 2004, 03:49 AM

Hi Joe

I'm no expert on this but would think that the PC, soundcard and external psu would need to have their grounds connected at some point in order to share the same 0V.

In a CDP with separate audio/dac board and decoder board, the 0V are connected from one board to the other. This is often done using the screen of the signal cable.

Does the 0V provide a screen in the USB cable?
Maybe a computer guru can help.

apolon34 · 26th November 2004, 05:09 PM

you have to connect the ground, of course !

just make sure your 5v supply is floating to avoid any problems (ie not connected to earth)

joeling39 · 28th November 2004, 12:56 PM

ok did a check on my USB HDD & found that the 0V reference is connected like the after picture. Used that as the basis & managed to get the whole thing to work. Please find attached some photos.

Regards,
Joe Ling

joeling39 · 28th November 2004, 12:58 PM

more photos. This one is shows how the power connectes to the USB. Would actually prefer to use a box that is shielded but this this all I have lying around.

Regards,
Joe Ling

joeling39 · 28th November 2004, 01:00 PM

The display of my clock conditioner showing input frequency from the PC

Regards,
Joe Ling

joeling39 · 28th November 2004, 01:02 PM

My PC. I am using it as a transport (CD transport)

Regards,
Joe Ling

joeling39 · 28th November 2004, 01:05 PM

more showoff pics. This is the view from behind my listening chair

Regards,
Joe Ling

26th November 2004, 01:42 AM	#2
Fin diyAudio Member Join Date: Dec 2003 Location: -	Why not use a small powered USB hub? __________________ Regards Fin

26th November 2004, 03:49 AM	#4
Fin diyAudio Member Join Date: Dec 2003 Location: -	Hi Joe I'm no expert on this but would think that the PC, soundcard and external psu would need to have their grounds connected at some point in order to share the same 0V. In a CDP with separate audio/dac board and decoder board, the 0V are connected from one board to the other. This is often done using the screen of the signal cable. Does the 0V provide a screen in the USB cable? Maybe a computer guru can help. __________________ Regards Fin

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26th November 2004, 02:43 AM	#3
joeling39 diyAudio Member Join Date: Jun 2002 Location: Malaysia	Dear Fin, Thanks for the query. Maybe it's time for me to disclose more : The USB device in question is a sound card mated to a clock conditioner (Apogee Big Ben). I want a very good quality 5V power supply to the USB sound card. My guess is that a power USB hub is not much better than the power supply from the PC. Please assist. Thanks. Regards, Joe Ling

26th November 2004, 05:09 PM	#5
apolon34 diyAudio Member Join Date: Jan 2004 Location: rouen	you have to connect the ground, of course ! just make sure your 5v supply is floating to avoid any problems (ie not connected to earth)

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