Not sure if any of you guys are electrical engineers? I’m not so might be a rubbish idea. The QC has no ground when used alone with guitar and headphones only and can be noisy. The solution is to plug one QC output to a grounded device. Would it be possible to create an adapter like the factory one but the 3rd pin on a UK plug could have a wire connected to a 1/4” input. Then when using QC with headphones only, connect the new adapter 1/4” to one of the QC outputs which would ground through the 3rd pin in the UK plug. Then when using with grounded speakers etc you can leave the 1/4” unplugged. Would this work theoretically?
Thanks
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I have thought of the same idea in the past, but never got round to trying it because I don’t have a problem to solve. I always have an XLR connected to my speakers anyway. I can’t see why it would’t work.
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Thanks for your reply. I must be the only person that uses this primarily as a practice device with headphones only to not annoy my family. So this issue must just affect me. I wish I had known before I bought and would have got a fractal fm9 instead as my old axe fx ii didn’t have to be connected to anything. Only sold it as it is not as portable as the QC. My mistake.
You may have already seen the previous posts but the Globtek PS Digi-Key part number: 1939-1233-ND works nicely for around $24 shipped in the US. Much more robust and solved the grounding artifacts that some have experienced, note I didn’t have the noise issues but wanted a spare PS just in case.
Note: If you get it, it comes with three tips, use the larger yellow tip etc., also before you push the tip in, ensure the polarity is correct for QC (center negative).
Are you sure that solves the noise issue caused by a missing connection to ground when only using headphones? I doubt that to be honest… Because a DC barrel connector simply has no ground connection as it only provides two contacts for + and - (the barrel itself and the inner tip). Maybe a supply like this can get rid of ‘dirty’ power from your rooms mains, but that should be all.
Every device that receives it’s power through one of those barrel plugs has this ‘problem’ (e.g. Line6 HX Stomp, Headrush Gigboard).
If you aren’t afraid of a little bit simple DIY stuff, you could try something like this guy did for establishing a connection to ground for his HX Stomp: HX Stomp ground noise solution - Helix - Line 6 Community
(sorry for linking the competitioner’s forum)
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I have never had the grounding noise that some have experienced when only the guitar and headphones are used but that PS was recommended by multiple users who indicated it solved their grounding noise issues. Otherwise, I do agree with your logic 
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I also experience just a very quiet faint noise when only using headphones. But the guitar / bass signal is significantly louder so that it does not bother me… It’s not much louder then the faint white noise active noise cancelling headphones produce when not listening to music (as a reference for those who own some ANC headphones). For practicing with headphones on the go that’s totally fine for me personally.