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DAC IV stages
John_Siau
post Mar 4 2013, 17:28
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QUOTE (Arnold B. Krueger @ Feb 27 2013, 10:30) *
QUOTE (John_Siau @ Feb 27 2013, 09:10) *
In the tests we ran (Macbook vs. DAC1), the gain control was 16-bit undithered due to the fact that iTunes 7.X was not available at the time. The iTunes volume control was used in the test. The existence of 16-bit truncation was verified with an AP System 2, and can be heard in the fade-out at the end of the samples I posted on this forum.


Can this be summarized as saying that those tests wouldn't produce the same results if repeated today using up-to-date iTunes software?

The results may be different. The truncation artifact would be eliminated if it was caused by iTunes. The operating system may also need to be updated to eliminate the truncation. These changes should eliminate the truncation artifact (one of two artifacts that made ABX detection easy). The second artifact (noise) probably would not change.

One could argue about which artifact is more objectionable, but I have no intention of doing that here. ABX tests are intended to detect audible differences and do not tell us anything about which "sounds better" when a difference is detected.


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Soap
post Mar 5 2013, 01:11
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QUOTE (John_Siau @ Mar 4 2013, 11:28) *
QUOTE (Arnold B. Krueger @ Feb 27 2013, 10:30) *
QUOTE (John_Siau @ Feb 27 2013, 09:10) *
In the tests we ran (Macbook vs. DAC1), the gain control was 16-bit undithered due to the fact that iTunes 7.X was not available at the time. The iTunes volume control was used in the test. The existence of 16-bit truncation was verified with an AP System 2, and can be heard in the fade-out at the end of the samples I posted on this forum.


Can this be summarized as saying that those tests wouldn't produce the same results if repeated today using up-to-date iTunes software?

The results may be different. The truncation artifact would be eliminated if it was caused by iTunes. The operating system may also need to be updated to eliminate the truncation. These changes should eliminate the truncation artifact (one of two artifacts that made ABX detection easy). The second artifact (noise) probably would not change.


So the solution to a piece of software and/or an OS which implemented a mixer so poorly it truncates is to attach an expensive external DAC? So instead of just using free software which does its job competently or using an analog volume control (the MacBook Air tests at ~104dB of SNR, leaving plenty of room for other options) for $20 one should throw out the baby and buy your product?

This post has been edited by Soap: Mar 5 2013, 01:20


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Mach-X
post Mar 5 2013, 11:47
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Rather ironic that everybody is rather correct. The clip+ when the rockbox firmware is installed has near infinite volume settings, that attenuate very smoothly in nature, that would suggest to me, an analog gain adjustment.

However my Galaxy cellphone with wolfson wm8994 has both digital and analog adjustment. With stock firmware the analog is locked (probably for liability reasons as the amp is quite a beast), while the digital gain is adjusted in 8 steps. With the 'voodoo' software modification, the analog amp is unlocked, and the digital amp gets locked to max signal, theoretically improving SNR, as well as EMI, as in most cases with full bit depth, you are using much less gain on the analog amp smile.gif

Really cheap pmps seem to use digital only with a fixed analog gain. So it would seem both implementations are used.
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