OK guys I figured it out and it's a bit crazy. First, I didn't have auto-tracking enabled on my Vsweep test. The only way to get their 106dB SINAD is to adjust the Master Vol to 82.5dB using a 0dBFS input signal which corresponds to 4Vrms output. The problem when doing Vsweep vs distortion tests is that won't run the preamp into clipping since it's capable of outputting 12Vrms. Once I adjust the master volume up, SINAD gets reduced at all levels. See attached graphs. \n\n\nMaster Vol: 82.5dB, HDMI Input 0dBFs\n\n\nHere I plot output level vs distortion. As you can see with the Master set to 82.5, I can get the 106dB SINAD but there isn't enough drive to reach clipping. I had to increase the Master Vol to 95dB and rerun the test to get to max level but SINAD suffered as a result.