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USB - TosLink - SPDIF - Window Drivers effect on UHA-6SmkII DAC-Amp combo

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atomicbob:
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

atomicbob:
JRiver as program material source


100 Hz sine  -0.1 dBFS USB JRiver Direct Sound




100 Hz sine  -0.1 dBFS USB JRiver ASIO4ALL




100 Hz sine  -0.1 dBFS USB JRiver Kernel Streaming




100 Hz sine  -0.1 dBFS USB JRiver WASAPI

atomicbob:
THD  THD+N


THD  THD+N  -0.1dBFS - USB Windows SoundMapper




THD  THD+N  -0.1dBFS - USB Windows driver - Speakers USB Audio DAC



There doesn't appear to be any difference whether the driver is selected directly or through the sound mapper in Windows


THD  THD+N  -0.1dBFS - USB ASIO4ALL




THD  THD+N  -0.1dBFS - TosLink




THD  THD+N  -0.1dBFS - SPDIF




Windows native drivers are clearly modifying the sample data before sending to the USB interface.
If someone knows how to reliably stop this modification, please speak up and share your knowledge.

atomicbob:
IMD vs. amplitude


IMD - USB Windows SoundMapper




IMD - USB ASIO4ALL




IMD - TosLink




IMD - SPDIF




Jitter


Jitter - USB Windows SoundMapper




Jitter - USB ASIO4ALL




Jitter - TosLink




Jitter - SPDIF

atomicbob:
Dynamic Range


Dynamic Range - USB Windows SoundMapper




Dynamic Range - USB ASIO4ALL




Dynamic Range - TosLink




Dynamic Range - SPDIF




Amplitude Linearity


Amplitude Linearity- USB Windows SoundMapper




Amplitude Linearity- USB ASIO4ALL



WTF???!!! I repeated this one several times on different days and obtained the very similar results each time. So it would appear ASIO4ALL is altering data at a very low level??


Amplitude Linearity- TosLink




Amplitude Linearity- SPDIF

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