I've been searching the Internet, and I can't find a single reference to
whether Firewire connections (specifically to the MOTU 896) can pose a
potential ground loop issue.

I'm going to rewire a medium-ambitious home studio, and I know that there are
ground loop problems between the outlets I'm going to need to use, so I'm
trying to minimize the number of things that must talk between the 2 circuits,
and make sure they are connected balanced, and with grounds lifted.

To this end, I was figuring to put all the computer equimpent on one circuit,
and all the audio equipment on the other circuit (considering the 896 to be
audio gear since it talks mostly to audio).

This all leaves me wondering, though, if the Firewire connection between the
computer and the 896 could be a path for ground loop current. Does anyone
know what kind of isolation is or is not in the Firewire connections?

"Steve Jorgensen" wrote in message


I've been searching the Internet, and I can't find a single reference
to whether Firewire connections (specifically to the MOTU 896) can
pose a potential ground loop issue.


Here's some articles that may shed some light:

http://www.machinedesign.com/ASP/str...Site/viewSelec
tedArticle.asp

This article mentions optically-based IEEE 1394 (Firewire)

http://www.agere.com/client/docs/AP98074-01.pdf

This article mentions some strategies for electrically-isolated copper-based
1394

http://www.ramelectronics.net/html/1394_fiber.html

http://www.multidyne.com/pdf/DV1394.pdf

http://fwdepot.com/thestore/product_...sCsid=4d07aa93
ca3d9d7fc76cc58e36d2455e

http://fwdepot.com/thestore/product_...roducts_id/422

http://www.cwol.com/firewire/newnex-...l-repeater.htm

This are commercial interfaces for optically-based 1394 which is known as
1394b

Steve Jorgensen wrote:
I've been searching the Internet, and I can't find a single reference to
whether Firewire connections (specifically to the MOTU 896) can pose a
potential ground loop issue.

So, plug two machines together with firewire, don't plug them into the
wall, and measure the resistance between their safety grounds. If there
is a dead short between the safety grounds of the two pieces of gear, then
the firewire link is tying the chassis together.

It's easy enough to measure. Much easier than spending your time searching
around on the net.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message


Steve Jorgensen wrote:

I've been searching the Internet, and I can't find a single
reference to whether Firewire connections (specifically to the MOTU
896) can pose a potential ground loop issue.

I guess how well google works depends on how well you can play "sounds
like..."

So, plug two machines together with firewire, don't plug them into the
wall, and measure the resistance between their safety grounds. If
there is a dead short between the safety grounds of the two pieces of
gear, then the firewire link is tying the chassis together.

It's easy enough to measure. Much easier than spending your time
searching around on the net.

True, but. The measure-what-you-got technique works for the equipment you
test, but without testing a fair amount of gear, you can't reasonably
extrapolate to the next piece of gear that walks on through the door.

OTOH, I did search around the net a bit and found that the current
implementation of firewire (IEEE 1394) can reasonably be expected to tie the
signal ground, power ground, and shield ground together inside the
equipment.

IEEE1394 and USB are a whole 'nuther thing compared to 10BT and 100BTx, as
well as AES/EBU and TOSLink which include isolation transformers in many
(TOSLINK) or all (the rest of the list) good implementations.

Thanks Arny and Scott for the helpful replies.

Unfortunately, it looks like the optical options currently cost as much as the
896 itself, so I'll try Scott's suggestion first, measure the resistance, and
see if there's a problem to worry about. I guess I'll have to see if there's
something I can do about the power situation if it looks like there could be
an issue with ground loop on the Firewire.

On Tue, 09 Dec 2003 08:12:30 GMT, Steve Jorgensen
wrote:

I've been searching the Internet, and I can't find a single reference to
whether Firewire connections (specifically to the MOTU 896) can pose a
potential ground loop issue.

I'm going to rewire a medium-ambitious home studio, and I know that there are
ground loop problems between the outlets I'm going to need to use, so I'm
trying to minimize the number of things that must talk between the 2 circuits,
and make sure they are connected balanced, and with grounds lifted.

To this end, I was figuring to put all the computer equimpent on one circuit,
and all the audio equipment on the other circuit (considering the 896 to be
audio gear since it talks mostly to audio).

This all leaves me wondering, though, if the Firewire connection between the
computer and the 896 could be a path for ground loop current. Does anyone
know what kind of isolation is or is not in the Firewire connections?