- Written by John E. Johnson, Jr.
- Published on 10 May 2012
The Rein Audio X-DAC On the Bench
Distortion measurements were made within an 80 kHz bandwidth. The connections were XLR for the analog signal path, and coax or USB for the digital input. The bitstream format is specified on each graph, i.e., 24/48, 24/96, etc.
First, the coax S/PDIF results:
At 1 kHz, using a signal at 0dBFS (the highest loudness level that can be recorded without clipping), distortion was only 0.003%. Output (XLR) was 2 volts RMS.
Using the same signal, but at - 5 dB, distortion was still only 0.003%. The output dropped to 1.2 volts.
With 24/192 sampling, there were actually a few more distortion peaks than there were at 24/48 sampling.
With 19 kHz and 20 kHz sine waves, the B-A peak at 1 kHz was 110 dB bewlow the fundamentals.
IMD was extremely low, at 0.002%.
The measured frequency response was ruler flat out to 48 kHz, using 24/96 sampling.
Now, let's take a look at the results using the USB interface.
At 1 kHz, and 16/44.1 sampling (which is most likely what the typical consumer would be using, having ripped their CDs to their computer), distortion was more than with using the S/PDIF, at 0.04% with the signal at 0 dB (first graph below), and 0.002% at -5 dB (second graph below). The output voltage was about the same at 0 dB test signal as with the S/PDIF inputs (2 volts RMS).
Using the coax digital input (S/PDIF), and 16/44.1 sampling, with the 1 kHz output at 0 dB, distortion was 0.004%, which is lower than it was using the USB input (0.04%), and at - 5 dB, S/PDIF distortion was 0.005%, which is actually higher (considered an insignifcant difference) than it was with the USB input (0.002%).