We used a Meitner LIM detector. It consists of a VERY low jitter (10 pS RMS or so) master crystal oscillator, a phase comparator, and an output filter to control the measurement bandwidth. The resulting signal is fed to an Audio Precision System II for either RMS measurement or FFT analysis. The rig is very sensitive, and clearly shows differences between different clock sources. Calibration is determined by using a digitally-synthesized waveform generator (Analogic 2030A) to inject a known amount of phase modulation. The output is noted, then used to calculate the calibration factor.Due to our new PLL (Phase Lock Loop) implementation, Pro Tools|HD systems are rather immune to the effects of externally-applied jitter, such as from the Nanosyncs (or any other sync peripheral).