I bought the Sparrow to be able to make use of my various balanced cables on IEMs while listening music from my phone, and I do enjoy the sound it produced very much.
Though, what has brought down my excitement somewhat is the constant electronic interference I get from my phone while using the Sparrow.
The original short braided cable that came with the Sparrow produced interference from the get-go, and based on the info in this thread I purchased the Oeaudio's oeotg cable. Unfortunately, I'm experiencing interference with the oeotg's cable as well, but not as much as with the original cable.
I contacted the company to get a replacement cable as per the instructions in this thread, because the company was kind enough to send it for free. Again, the lengthier replacement cable produced interference - while perhaps slightly less than the original cable, still more than the oeotg cable.
So, I'm left with only being able to use the Sparrow through my phone if I place it in airplane mode, which is not ideal since that means I'm not reachable on my phone when listening to music on it. Still, I do like the Sparrow so much that I'm willing to live with it for now. I suspect that my phone might be the culprit (Honor brand) and somehow especially incompatible with the Sparrow, so I hope when I upgrade my phone later this year that my problems will go away.
I've been thinking about making a Faraday pouch of some kind for the Sparrow or just wrapping it up in EMF shielding tape, but I haven't undertaken that effort yet since I'm hoping it's the phone that is causing the problem.
I've updated the firmware to the latest version, and my device was probably one of the earlier ones produced as I purchased it immediately after seeing a store in the EU having it in stock after launch.
TL;DR
The Sparrow is a great device when it comes to listening to music via the balanced output, but it does have a design flaw, which causes electronic interference when paired with certain devices regardless of the firmware version or the cables used.