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-   -   Galvanic Isolators (http://www.diyaudio.com/forums/pc-based/210889-galvanic-isolators.html)

Tom Mulcahy 16th April 2012 04:47 PM

Galvanic Isolators
 
Hello.
Could anybody help please?
I wish to connect my laptop (USB to USB), to an rCam DAC.
Going direct, as you can imagine, the background noise is horrific!
I had an isolator from Brown Bear (Denmark), but it gave up the ghost after a few hours use.
When it worked it was very good.
I'm now using Wireless connection, but a USB cable would be useful on occasion.
Any suggestions greatly appreciated.
Thank you, Tom M.

Pano 16th April 2012 05:30 PM

I have seen USB isolator chips before, but of course can't remember where. :xeye:

Your problem is a bit surprising. I rarely have any trouble at all with USB to DAC - unless the cables runs are very long and grounds are coming from different mains receptacles. What's your setup like?

infinia 16th April 2012 05:40 PM

1 Attachment(s)
Hi,
looks like there is already an internal isolator see attached u101.
Have you tried contacting Arcam for their solution? maybe some issue with grounding DAC wall wart or laptop AC/DC power brick. Use laptop batteries or SPDIF and/ or optical.
need more trouble shooting w Arcam in the loop.
> maybe try a new higher DC supply for this DAC try ~ 9V DC instead of theirs which is only 6V. also add or take away an earth ground?

staggerlee 16th April 2012 05:51 PM

I use one of these to connect my Alix board to my DAC.

phofman 16th April 2012 05:59 PM

Quote:

Originally Posted by infinia (Post 2987721)
Hi,
looks like there is already an internal isolator see attached u101.

A galvanic isolation would not use the USB power supply and ground directly in the device. That IC is just an EMI filter and line terminator http://www.datasheetcatalog.org/data...cs/mXyxuss.pdf

Dane 16th April 2012 06:22 PM

Quote:

Originally Posted by staggerlee (Post 2987735)
I use one of these to connect my Alix board to my DAC.

Me too.

infinia 16th April 2012 06:39 PM

Quote:

Originally Posted by phofman (Post 2987752)
A galvanic isolation would not use the USB power supply and ground directly in the device. That IC is just an EMI filter and line terminator http://www.datasheetcatalog.org/data...cs/mXyxuss.pdf

thanks for looking that part up. yes not a real isolator I should of known cause the 3.VDC connection on the input side and common ground.
6V shown on schematic seems low for 3T linear reg. ripple rejection, but probably measures higher in real life. need to use O-scope to check.

qusp 16th April 2012 10:06 PM

Quote:

Originally Posted by Tom Mulcahy (Post 2987648)
Hello.
Could anybody help please?
I wish to connect my laptop (USB to USB), to an rCam DAC.
Going direct, as you can imagine, the background noise is horrific!
I had an isolator from Brown Bear (Denmark), but it gave up the ghost after a few hours use.
When it worked it was very good.
I'm now using Wireless connection, but a USB cable would be useful on occasion.
Any suggestions greatly appreciated.
Thank you, Tom M.

actually no I cant imagine, like Pano I dont have this kind of experience of horrific noise, any half way decent modern USB implementation is pretty transparent, in fact its gotten ti the point where IMO it has left everything elsed behind. I suspect there is something wrong with the way you have connected everything up.

wwenze 17th April 2012 01:19 AM

I have this kind of experience of horrific noise, with a Tascam USB interface, with another coax DAC, with sound cards... Grounding configuration kills, so half of the population probably won't notice this problem.

Redshift187 22nd April 2012 06:02 PM

The only time I've ever had noise from a PC connected to an amp (which was noisy with the onboard and also with a USB DAC) it turned out to be the power supply in the amp causing the problem, and was *not* the ground.


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