And this attachment shows the frequency response through the aux inputs. Basically, the PC's audio output is fed to the EMPEG's aux inputs. And then the EMPEG's outputs are fed back into the soundcard.

For reference I replaced the EMPEG in this test chain with a set RCA barrel connectors, without changing anything else in the test setup (so that the input and output patch cables were still in the loop). With the EMPEG barreled out of the chain, the response was flat from 20Hz to 20kHz. The measured response of this test is in the next reply.