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Feedback loop w/ Neumann KH120 + E1DA 9038S

Joined
Jan 18, 2020
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#1
Greetings,

I recently purchased a E1DA 9038S DAC and I paired it with a 2.5mm fully balanced cable:

https://www.amazon.com/Sukira-Balan...eywords=2.5mm+balanced&qid=1579273607&sr=8-20

However, when I connect both of my Neumann KH120’s there is feedback that builds up very quickly until the 120’s protection kicks in (lights turn red). I’ve tried different cables, ground lift switch and different electric outlets but same result. The feedback does NOT happen if only 1 speaker is connected. Additionally, this issue does not occur on my JBL 305 XLR or my Adam XLR inputs. Only the KH120s? ive tried using both my Win10 PC and my S10 5G phone, same result. Interestingly, the 9038S doesn't even need to be powered on for the feedback to buildup - simply wiring everything together and powering the KH120s will do it.

My Benchmark DAC2 works just fine with both KH120’s via XLR. The 9038S works great with my Westone W50 IEMs so I don’t feel like its defective, just some kind of incompatibility perhaps? Ivan, the designer, is thinking that it's related to the 9038S not having GND but he's had customers somehow 'build' a GND via the USB C shielding. I'd be open to that but I have no idea where to start?

Any suggestions? Thank you!!!
 
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T
Joined
Jan 18, 2020
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Thread Starter #3
I think I found the problem - none of the outlets in my house are grounded! With my Neumanns unplugged, my surge strips light up "ground fault." When I plug them back in, the ground fault indicator shuts off. So my Neumann's have been acting as ground for my HTPC, TV, etc. this entire time? Strangely if every single device is connected to the same outlet via extension/surge strip, things play fine! Although that 1 outlet isn't grounded - I don't understand...
 
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