Yes, exactly that. Obviously not an issue w a phone and an external power supply.Presumably you mean when taking the 3.5mm output from the PC, while concurrently charging (the same device that the 3.5mm is going to) via a separate USB connection from the PC? That's why the context was solely with s24 [phone not connected to anything else]. The data signal is from the s24, the power from wherever.
I get hiccups or micro dropouts from PC due to having certain other (non-USB) equipment connected and running concurrently with the Alpha. Luckily I have no use for said other equipment while the Alpha's in use - so it serves as a reminder to turn it off. I haven't tested if lowering the sample frequency would help, I suspect it would.
With my Macbook, I can use the Midi App to set the output. I'm assuming you can do something similar w Windows.
And yes, having other things attached to the PC and also other jobs running can also effect the quality of the sound.