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Two DACs or Preamp or...?

6th0

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I have been chasing down a ground loop and decided I just to go balanced.

My current setup is PC (APO Equalizer) --> USB --> E30 DAC --> RCA --> L30 headphone amp --> RCA --> Sabaj A20a.

I have a "work from home" setup and like listening to the speakers instead of headphones. What I like about the setup is that when I get a call from work on my Polycom VOIP phone I just flick a switch on the L30 to cut off the music and take my call. I have a different line via Teams through my PC/L30, so that does take some some quick reflexes to turn off the music at the PC level and pick up the headphones.

Some thoughts are:

1) Put a Topping D10 balanced on the USB and run TRS to RCA to the amp. For headphones I could use optical to the E30, RCA to the L30. It would be two separate paths. I sadly lose the physical switch to shut down quickly (and no remote with the D10). I also suspect that I will be forever switching the playback devices in Windows.
2) Preamp? PC --> E30 --> active preamp to convert unbalanced to balanced. RCA into the preamp, RCA to the L30, balanced XLR to the A20a. Any suggestions on an inexpensive preamp like this?
3) D30 Pro. Pricey ($400) just to get XLR and about the same level of performance I already have with the E30
4) ifi USB isolator and power supply to break the hum my setup alone.

Any suggestions?

Thanks!
 

sjeesjie

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Have you tried interconnect cables with ground loop isolators yet? Definitely a cheaper option than going full balanced.
Have you tracked down which of your devices form the loop?
 
OP
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6th0

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The ground loop is definitely traveling from the USB cable from the PC to the E30. When I move my wireless mouse (connected by a USB receiver), the static increases. I must have the volume high and music off (or a lull in the music if I am playing loudly) for me to hear it, but it's there!
 

Trell

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On this forum there have been posts about devices for fixing the ground loop from the USB. Galvanic isolation?
 
OP
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6th0

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Some more clues...
I put the PC on the same power brick as the audio gear. The hum was louder than when it was on a different outlet! I then put a cheater plug on my amp (right now it is a DA-9 but in a couple days it will be the A20a)--hum gone! If I had the cheater on with a different outlet then I get a much quieter hum.

Doing some reading on the forum, galvanic isolation seems to really mean an isolation transformer or a USB isolator with its own power supply?
 

puppet

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If I use power from the wall to the E30 I get hum. If it's power is drawn off the laptop ... no hum.
 
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