Presented is a collection of measurements depicting the behavioral differences of interfaces and USB device drivers for the Leckerton UHA-6S
mkII. I like the sound of this DAC / Amp combo and it has multiple interfaces so it is a convenient device with which to experiment. Some of
these differences may or may not extrapolate to other devices such as the SPDIF vs. Toslink vs. USB comparisons. Several of the USB device
driver issues are problematic for all DACs. In particular, Windows drivers may not deliver sample accurate data as will be shown.
From this data it is apparent why Nick Kettman may prefer a clean TosLink feed with SPDIF being very close behind. USB benefits from a player that can direct data out through WASAPI. Direct Sound is evil, if you care about your music.
The data presented were collected as follows:
1. PrismSound dScope III
2. DAC unbalanced output RCA
3. 100 Kohm load used for measurements dScope measurements
4. 44 KHz sample rate, 24 bit depth
5. USB input cable - the one provided by Leckerton audio in the box
6. S/PDIF input - Canare broadcast grade 75 ohm BNC cable
7. TosLink - Mediabridge 0.5 meter
8. Unbalanced cable Radio Shack nothing special 3.5mm TRS to stereo RCA
9. Vaunix Lab Brick USB hub
10. output gain switch set to low position
Tests were run with 0dBFS ~= 600 mVpp. This level would be consistent with sound levels of 80 dBC avg and 89 dBC peaks for
HD600 or HD650 headphones if the program material had a Peak to Average of 9 dB.These first two graphs demonstrate the Windows driver issue which motivated this comparison.100 Hz sine -0.1 dBFS USB - Windows Sound Mapper
100 Hz sine -0.2 dBFS USB - Windows Sound Mapper
Note how at -0.1 dBFS there is a rather large amount of harmonic distortion not present when the stimulus is sent at -0.2 dBFS
100 Hz sine -0.1 dBFS USB - Windows driver - Speakers USB Audio DAC
100 Hz sine -0.1 dBFS USB - ASIO4ALL
100 Hz sine -0.1 dBFS TosLink
100 Hz sine -0.1 dBFS SPDIF
