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In my setup I'm using a music player connected to an audio mixer in an unbalanced connection that runs over 15m. In general I don't get too much noise, but when the player is unplugged from the cable (and the cable remains plugged into the mixer) OR when the player goes into standby mode, a loud buzz comes out of the mixer (even through its digital USB output).

My question is, is this due to the fact that I'm using unbalanced connection over a long distance or is there something else happening?

If the problem is the unbalanced connection, how can I rectify this? The player is Shanling M0 Pro which supports both balanced (4.4mm) and unbalanced (3.5mm) outputs, and the audio mixer is Yamaha AG06 which only supports unbalanced line-level inputs (its balanced inputs are only mic-level). Can I use a passive DI box in reverse to run a long cable from Shanling's balanced output to the DI box's "would-normally-be output", and then connect the unbalanced DI box's "would-normally-be input" via a short cable to the audio mixer's input? Will the DI box perform the noise cancellation that a balanced amp/mixer would have performed without changing the signal level (i.e. it needs to remain line-level)? Or alternatively, would this do what I'm describing: https://artproaudio.com/product/cleanbox-pro-dual-channel-level-converter/

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    When the cable is unplugged it becomes an antenna so it's no wonder at all that it picks up EM noise generated nearby which is then amplified by the rest of the system. This shouldn't happen when the player goes on standby, however, because the shield of the cable should still be grounded even when the player is off. If you already own a passive DI box, you have nothing to lose by trying it to see if helps with the noise. If not, might not make sense to spend money on one. Have you tried the DI box between an unbalanced out and a mic input? That's what DI boxes are for. Commented Feb 23 at 4:44
  • Thanks for the explanation. Unfortunately I don’t have a DI box so can’t try… I wonder what’s happening in the circuit when player goes to sleep. I know it makes two popping sounds when it sleeps and again when it wakes up. Commented Feb 23 at 4:52
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    Oh is the player battery powered? That might explain it. The connection might float when it turns off and then it's an antenna again. 15m is pretty long for an unbalanced connection even when it is grounded on both sides. You could probably use a mic input as a balanced line level input. Engage the pad and lower the mic pre gain. You probably just need a 1/4" TRS to XLR adapter. Commented Feb 23 at 5:11
  • Yeah, it's battery powered. Thank you for your suggestion, I'll try it! Though the mixer only has two mic inputs and occasionally I need both, so the ideal solution would be to have a device that can convert from line-level balanced to line-level unbalanced while eliminating the noise in the circuit while doing so. Luckily though I just discovered that I can disable the auto-standby on the mixer, so that's a workaround as well. Commented Feb 23 at 5:19

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The Shanling has Bluetooth 5.0. You should just buy a BT receiver and use the RCA input on the mixer

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  • Lol, I was just about to post that that's exactly what I've done! Except there's one caveat... When Shanling goes to sleep it disconnects from the BT receiver which then gives a sound prompt "Disconnected and turns itself off... I run public events with this setup and so this kind of thing is not acceptable. The only workaround is to disable the auto-standby of the player, and if I do that I can go back to using the cable (as it will be shielded), but problem is battery dies quickly then, but oh well... Can't have it perfect :) Guess I'll just have to keep it plugged in when not in use. Commented Feb 29 at 3:43
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    @AaylaSecura bummer. You might be able to disable the voice prompts but I guess it depends on the type you got. I bought one for a high school’s gym that doesn’t make any noises when it connects or disconnects. Commented Feb 29 at 7:44
  • Yeah, for this one I can't disable them. I'll look for a BT receiver that 1) doesn't have voice prompts and 2) doesn't turn off automatically (cause that's the second problem: it requires someone to physically walk to it and turn it back on, negating the whole purpose of having the player a long distance form the mixer) Commented Feb 29 at 18:44

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