Observations Both are excellent measuring amps at these realistic power levels and loads. Red is THX AAA 789. Blue is Jotunheim. Purple is where the plots intersect. Jotunheim has a slightly higher noise floor. At -140db, no one will hear this. THX AAA 789 has a few harmonic spikes from power mains hum. At -125db, no one will hear this. Distortion characteristics at 1kHz look extremely similar. Notes: AverLAB output set to 8.23dBu. I figured this would be representative of consumer DAC output levels. The volume knob was adjusted accordingly to get -3.0dBu (within +/-0.1db) on the balanced outputs. The load was 330ohms to approximate to the nominal impedance of Sennheiser HD6## headphones. Both L and R channels are driven. The THX AAA 789 exhibited a sharp AC mains spike near -100db when the Jotenheim chassis was placed on top of it. I figured the big power transformer on the Jotunheim messes with a few things. I wouldn't worry about it. You can't hear the hum at -100db unless you are Amir. If you are super paranoid about measurements, then don't place any magnetics (transformers) near the THX AAA 789 chassis.