Re: [LAU] USB audio interfaces >= 8 channels

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To: Fons Adriaensen <fons@...>
Cc: A list for linux audio users <linux-audio-user@...>
Date: Tuesday, May 15, 2012 - 6:44 pm

On 05/15/2012 06:10 PM, Fons Adriaensen wrote:

Excuse my newbie question, but I'm not experienced with SPDIF.

Can one [word-clock] sync two devices using SPDIF or ADAT and still use
the analog I/O on both? -- Is that hardware specific or is there a
standard for that?

I assume the master-device will need to send a signal via SPDIF.

I'll check later if the 1818VSL can do both: output to SPDIF and analog
at the same time. but I don't know if I can do that remotely. What I do
already know is that the clock-source for each input can be configured
individually. but I'm still waiting for Brian to connect the device. my
ssh login already works..

>> What is not clear to me is

Here it mainly concerns the outputs: In my case there's a ground loop
between my Screen (Asus VE278) and the active speakers when connected
via computer and an USB UA-25 (not UA25-ex which features a ground-lift
switch) -> 1/4inch TRS -> B2031A speakers.

Disconnecting either the screen or the speakers (and using headphones)
works, otherwise there's a hum on the system; luckily no sparks, no
x-runs, either :)

A multimeter shows a constant 1mA current and ~3-4mV AC potential.
(measured between the USB-shielding of the PC and the disconnected
USB-cable of the UA25) when the screen is connected.

Both the screen as well as the speakers (and computer) are connected to
the same power-stripe and share the ground.

Fun-fact: When disconnecting the screen the potential between USB and PC
goes up to ~150mV (IFF the computer is not battery powered otherwise
it's 0) but the current drops to nil.

/me is pondering to cut the ground-wire from the screen.. but I have so
far refrained from doing that.

Anyway at some point the interface may end up on stage somewhere and
ground-lifting may be required for the inputs, too. Although in that
case I'll likely have some ground-lifting DI-boxes around.

robin
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Messages in current thread:
[LAU] USB audio interfaces &gt;= 8 channels, Robin Gareus, (Tue May 15, 10:07 am)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fons Adriaensen, (Tue May 15, 4:10 pm)
Re: [LAU] USB audio interfaces >= 8 channels, Robin Gareus, (Tue May 15, 6:44 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fons Adriaensen, (Tue May 15, 8:59 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Paul Davis, (Tue May 15, 10:34 am)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Robin Gareus, (Tue May 15, 10:41 am)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fons Adriaensen, (Tue May 15, 12:36 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Robin Gareus, (Tue May 15, 1:31 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Clemens Ladisch, (Tue May 15, 6:03 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Robin Gareus, (Tue May 15, 11:24 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Paul Davis, (Tue May 15, 8:16 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Robin Gareus, (Wed May 16, 9:28 am)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fernando Lopez-Lezcano, (Wed May 16, 11:13 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Paul Davis, (Wed May 16, 2:14 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fernando Lopez-Lezcano, (Tue May 15, 5:10 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Emanuel Rumpf, (Tue May 15, 8:52 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Fernando Lopez-Lezcano, (Tue May 15, 5:11 pm)
Re: [LAU] USB audio interfaces &gt;= 8 channels, Paul Davis, (Tue May 15, 11:03 am)