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Old 22nd August 2011, 01:58 AM   #21
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Some USB DACs though have isolation at DC ('galvanic isolation') - so the audio side is not referenced to laptop 0V. They're still susceptible to CM nose though, depending on the coupling capacitance across the isolators.
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Old 23rd August 2011, 12:36 AM   #22
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Sorry I just noticed how old this thread is, but can confirm that disconnecting ground on power supply does work. It's not a safety ground for a metal chassis, it seems to just be used as a reference. I'm not advocating disconnecting the ground, just saying that it worked for me is all :-)
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Old 23rd August 2011, 01:39 PM   #23
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True galvanic isolation is best done with audio transformers in the lines between the laptop and amp. Radio engineers have known this as long as the transmitter sites were remote from the studio and phone lines were used to connect the two. If you want a cheap test for this, get two similar old phone modems and use the transformers from them to do the isolation, or buy some from LINE MATCHING TRANSFORMER 1:1, 600 OHM |
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