Ok thanks - I wondered how the term ground loop came up. Maybe a Negative Loop would be more accurate. Still, I find it strange the condition occurs. The power supply (USB 5v) and audio output common to the left & right channels are simply sharing the same negative connection which should be fine. I may have a 600 ohm audio transformer that I’ll try for one channel. If successful will get second. That would be less expensive than the couplers I saw for around $20.
I’m finally getting away from CDs - I prefer CD-RWs since I like to add/change content frequently, but with this new laptop the quality has been poor. All have skips, even CR-R disks have intermittent clicking sounds like an amp being overdriven. I’ve been using the Sansa Clip with a low power (legal) FM stereo transmitter for listening around the house and outside. The Sansa has absolutlely no trouble connected to a USB adaptor which is connected to an old 12v power supply, perfect audio. The same power supply powers the transmitter.
Out of curiosity I’ll connect the Sansa to an older car that still has only a CD & cassette player and use one of those cassette adaptors. I know - cave man technology. But I’d suspect no ground loop trouble since the audio is being inductively coupled to the cassette player head.
