The following test measurements, which I made using the Audio Precision Analyser, were taken during the course of my review of the Burl Audio B2 Bomber A-D and D-A converters (/sos/nov10/articles/burlb2.htm).
This shows that the B2 A-D converter has very little distortion, but it is predominantly odd-order.For the A-D converter, THD+N is well below -114dBFS for all input levels up to -25dBFS, above which it rises gently over about 30dB as a progressive odd-order distortion.This chart for the D-A converter compares the noise floor and spectrum when converting a single tone signal using the embedded 44.1kHz clock (lower traces) and the internal clock running at 48kHz (upper traces). The latter clearly shows a significantly higher noise floor and an entire stream of aliasing distortions.This graph reveals how the distortion products created by the D-A converter reduce in level with the input signal. An input of -1dBFS produces the distortion shown by the light green bars – most odd order harmonics. An input of -10dBFS produces less distortion (red bars), but still mostly odd harmonics, while an input of -20dBFS produces very little distortion (blue bars) and with little discernable harmonic colouration.
Published November 2010