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Old 16th April 2012, 04:47 PM   #1
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Default 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.
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Old 16th April 2012, 05:30 PM   #2
Pano is offline Pano  United States
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I have seen USB isolator chips before, but of course can't remember where.

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?
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Old 16th April 2012, 05:40 PM   #3
infinia is offline infinia  United States
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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?
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Old 16th April 2012, 05:51 PM   #4
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I use one of these to connect my Alix board to my DAC.
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Old 16th April 2012, 05:59 PM   #5
phofman is offline phofman  Czech Republic
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Quote:
Originally Posted by infinia View Post
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
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Old 16th April 2012, 06:22 PM   #6
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Quote:
Originally Posted by staggerlee View Post
I use one of these to connect my Alix board to my DAC.
Me too.
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Old 16th April 2012, 06:39 PM   #7
infinia is offline infinia  United States
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Quote:
Originally Posted by phofman View Post
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.
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Last edited by infinia; 16th April 2012 at 06:43 PM.
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Old 16th April 2012, 10:06 PM   #8
qusp is offline qusp  Australia
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Quote:
Originally Posted by Tom Mulcahy View Post
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.
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Old 17th April 2012, 01:19 AM   #9
wwenze is offline wwenze  Singapore
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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.
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Old 22nd April 2012, 06:02 PM   #10
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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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