The output voltage complies to the Red Book spec’s at only slightly above 2V at 0 dBFS. The frequency response is ruler straigt up to 10 kHz where it only slightly drops to 0,4 dB at 50 kHz. This is often intentionally done to get better phase and impulse response and 0,4 dB at 50 kHz is inaudible.
Looking at the distortion and noise we see a very clean spectrum. This measurement is done using a multitone measurement where a number of tones were sent into the d/-a-converter while measurements were made at other frequencies in between the stimuli. This prevents the converter from muting.
Linearity is close to perfect down to -90 dBFS and very good down to -110 dBFS. From there larger deviations occur, most likely due to noise and/or power supply interference.
Using the Audio Precision jitter test signal shows two small side bands at only 100 Hz from the 12 kHz stimulus and a very strange signal at 9600 Hz.
When an external source (MacBook Pro and M2Tech hiFace Two) was connected, the J-Test signal gives a clean measurement. The low spikes at regular intervals are a part of the test signal.