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mohfuu
39
Sep 4, 2019
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I'm experiencing a low electrical buzz or hum while using the THX 789 amp which began suddenly after listening to it for a few hours without issues. I've got the 789 hooked up to an Airist R2R dac with RCA cables, the dac is hooked up to my PC with a toslink cable and I'm listening through MrSpeakers Ether CX Headphones. My computer, the dac and the amp are connected to power from the same outlet, I live in europe so I've gotten a hold of two US to EU adapters to connect the amp and dac to power, the adapters do not convert voltage. I've been fiddling around with the amp and dac, I'm no genius when it comes to electronics but I'd really like to get this remedied in any way possible so I've been disconnecting cables from the amp and dac while wearing headphones to see how it affects the buzz in hopes that I might be able to eliminate or narrow down to the cause of the buzz.
  • if I disconnect the RCA cables, the buzz persists.
  • if I disconnect power to the amp, but still am connected to the dac via RCA the buzz persists.
  • if I disconnect power to the amp and dac, as expected, the buzz stops.
Now I don't know if this boils down to the units malfunctioning, or that I'm using an incorrect adapter, or the fact that it's all powered through the same outlet that my computer is connected to. I've noticed if I touch the aluminium casing of the amplifier the buzzing drops to an inaudible or almost inaudible level, and if I pick up my phone while charging through USB connected to my computer the buzzing is very accentuated, but if I hold it while charging from a different source there is hardly a difference, but if I touch, for example, the metallic leg of my desk it's only slightly accentuated. Oh, and I've also noticed wearing slippers or lifting my feet of the ground seem to lessen the buzz. I haven't tried connecting the amp and dac to a different outlet than my computer but it seems like the appropriate next step (to an uninformed commoner like myself) which I'll do as soon as I get my hands on an extension cord. Any advice from electrical wizards, professional or otherwise, would be appreciated.
Sep 4, 2019
rawrus
74
Sep 5, 2019
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Try using your R-2R for a couple days, and report back. But my experience was buzzing using RCA Cables (the cheap ones that DVD players come with) They are very sensitive to electromagnetic fields because of poor shielding. IT COULD BE A GROUND LOOP. I have no idea how though because the THX or RDAC are not 3rd pronged to have ground But ... you may be somehow getting a ground loop. Or worst case scenario, Unit is faulty. Let me know what else you think. replying on a whim Sorry I didn't read your comment with my full attention...
Sep 5, 2019
haproot
17
Sep 5, 2019
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It does sound like a ground loop to me. Have you tried different headphones? Is it possible to plug the THX into a different outlet? I almost wonder if something funny happened to your power adapter.
(Edited)
Sep 5, 2019
mohfuu
39
Sep 5, 2019
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The mystery has been solved. As the excitement of getting new gear from the mail had left my body I managed to read the manual of the 789 in its entirety. It has an interesting paragraph pertaining to the lack of grounding in the 789 and furthermore mentions how it shares the ground of its audio source. Since my audio source was connected to my computer through a toslink or in other words an optical cable which doesn't transmit electricity, the system was ungrounded which I fixed by simply connecting the Airist dac to my computer with the USB cable that came with it. I guess the moral of the story is - always fully read the manual.
(Edited)
Sep 5, 2019
rawrus
74
Sep 5, 2019
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Really happy to hear that. Thanks for for sharing your experience!
Sep 5, 2019
greyscale
0
Sep 7, 2019
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Thank for the info. Was not aware 789 came with a manual. Is it paper or d/l pdf?
Sep 7, 2019
rawrus
74
Sep 7, 2019
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It seems to be a small A5 paper double sided. It seems to be basic stuff, but I gave it a read.
Sep 7, 2019
shoaibexpert
80
Aug 12, 2020
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Hi I am facing the same issue in exact same way you had described it. Did you happen to solve the Buzzing noise issue with the THX 789? Thanks
Aug 12, 2020
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