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Thread: WM8716 used in Caiman - how it was programmed

  1. #1
    Join Date: Jul 2013

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    I'm Krzysztof.

    Question WM8716 used in Caiman - how it was programmed

    Hello,
    I've found this description on the web about the potential of WM8716 D/A chip:

    The actual digital to analog conversion in the HD is handled by the Wolfson WM8716. The WM8716 combines a number of desirable features in a D-to-A chip. The ’16 can be programmed to use a “slow roll” digital interpolation filter. In listening tests, this results in a much more natural sound than the standard “fast roll-off” interpolation filter more commonly used in digital audio, even when the fast roll-off filters were apodizing or minimum phase. Other options frequently used in high-end audio are the NOS filter response (zeroth order holdover, frequently with additional analog filtering), which was used on the original devilsound DAC; soft knee minimum phase filters, pioneered by Ayre; or of course, the standard “brick wall” sinc filter, which is the traditional “standard” filter.

    There are other notable advantages with the Wolfson chip. The analog power supply for the chip can go be run at 4.5V, meaning it can be powered from a power rail derived from a filtered / down-regulated USB line. The chip requires no negative power supply, which additionally simplifies design. The DAC HD uses a charge-pump to generate a clean -4.5 V rail, for the op-amp output. However, one of the design goals was to minimize any switch-noise caused by the DC-DC conversion, by minimizing the amount of current drawn by the negative rail. The fewer things powered by the negative rail – in this case, only one op-amp per channel – the less the current draw, and the lower the switch noise. Minimizing the switching noise allows for a cleaner analog output, and cleaner power to the clocks, which helps minimize jitter.

    The WM8716 is run in software mode, and is programmed with a PIC microcontroller. The microcontroller puts the DAC chip into 24-bit I2S mode, selects the slow roll-off filter, and then goes into sleep mode.

    My question is which if these features are used in the 7520 Caiman SEG DAC? Who knows it?

  2. #2
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    The chip is used in hardware mode set for I2S and no filters.

  3. #3
    Join Date: Jul 2013

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    Does it mean, that it is the most clean path from the digital source to the analog output stage? Better than NOS?

  4. #4
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    That's a different issue. The only most clean path I know of in any commercial DAC is in the Bushmaster MKII.

  5. #5
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    Hm, so even if the DAC is put into hardware mode, somehow some kind of filtering has to be done somewhere. On the analogue part or sigma delta stage?

  6. #6
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    What does the datasheet say on that?

  7. #7
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    Well, not clear to me, because the datasheet says that the digital filtering can be bypassed using MODE8X, but I am not sure if it's hardware mode?

  8. #8
    Join Date: Jul 2013

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    Quote Originally Posted by mkrzych View Post
    Well, not clear to me, because the datasheet says that the digital filtering can be bypassed using MODE8X, but I am not sure if it's hardware mode?
    Anyone willing to explain me that?

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