CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Lobby => Amp and DAC Measurements => Topic started by: atomicbob on May 30, 2015, 09:26:09 PM
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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
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9955;image)
100 Hz sine -0.2 dBFS USB - Windows Sound Mapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9957;image)
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
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9959;image)
100 Hz sine -0.1 dBFS USB - ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9961;image)
100 Hz sine -0.1 dBFS TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9963;image)
100 Hz sine -0.1 dBFS SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9965;image)
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JRiver as program material source
100 Hz sine -0.1 dBFS USB JRiver Direct Sound
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9967;image)
100 Hz sine -0.1 dBFS USB JRiver ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9969;image)
100 Hz sine -0.1 dBFS USB JRiver Kernel Streaming
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9971;image)
100 Hz sine -0.1 dBFS USB JRiver WASAPI
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9973;image)
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THD THD+N
THD THD+N -0.1dBFS - USB Windows SoundMapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9975;image)
THD THD+N -0.1dBFS - USB Windows driver - Speakers USB Audio DAC
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9977;image)
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
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9979;image)
THD THD+N -0.1dBFS - TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9981;image)
THD THD+N -0.1dBFS - SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9983;image)
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.
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IMD vs. amplitude
IMD - USB Windows SoundMapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9985;image)
IMD - USB ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9987;image)
IMD - TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9989;image)
IMD - SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9991;image)
Jitter
Jitter - USB Windows SoundMapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9993;image)
Jitter - USB ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9995;image)
Jitter - TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9997;image)
Jitter - SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=9999;image)
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Dynamic Range
Dynamic Range - USB Windows SoundMapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10001;image)
Dynamic Range - USB ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10003;image)
Dynamic Range - TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10005;image)
Dynamic Range - SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10007;image)
Amplitude Linearity
Amplitude Linearity- USB Windows SoundMapper
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10009;image)
Amplitude Linearity- USB ASIO4ALL
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10011;image)
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
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10013;image)
Amplitude Linearity- SPDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2471.0;attach=10015;image)
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reserved.
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Looks better.
Wow an ENOB of 21 bits ... compared to the Yggy (measured at 18 bits) isn't half bad.
Strange that ASIO lowers the ENOB of the same DAC to 16 bits.
One starts to wonder if this is true for all DAC's or just this one.
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Moral of the story: which driver is used to send data over USB matters a lot.
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The UHA-6SmkII is spec'd (http://www.leckertonaudio.com/products/uha-6s-mkii/) as only being capable of "up to 48kHz/16-bit" over USB. You seem to be using 24-bit and 32-bit sources. I'm wondering if the some of the deficiencies in the USB ASIO4ALL measurements are due to ASIO4ALL being configured to truncate instead of dither.
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This is excellent work - correlates to my listening experience (preference for WASAPI over all other outputs esp. now we have MMCSS). Pretty much all of these should be bit perfect and free from dropouts etc?
Will probably do nothing for the flat earth naysayers but still good data.