Thanks for the quick response.
First of all, this is not an issue with my converter, which is a Fireface 400. The sound is inherent in the synthesizer...I program it using the headphone out. Second of all, this is not an issue of harmonics or a "tone an octave up." Did you not hear the digital buzzing at the end of the sound? Third, this was recorded at 24/88.2 with a 16bit quantizing plug-in on the master track and nothing else.
So, you think this is an issue of how the synthesizer is plugged in? It's plugged into a surge protected power strip.
"The Jupiter-4 will be tatooed on my heart for ever."