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Thread: New Playback Designs Dream Series DAC and Digital Transport

  1. #21
    VIP/Donor [VIP/Donor] microstrip's Avatar
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    Quote Originally Posted by Elberoth View Post
    1. The link is broken.
    2. It seems the pics shows XOs (crystal oscilators) not MEMS.

    So far, all the papers I was able to finds show that XO have much lower phase noise than MEMS. Which makes sense, as MEMS oscillators utilize a Phase Locked Loop (PLL) design with a MEMS resonator being phase locked to a VCO in an M/N synthesizer loop. The phase noise level of the MEMS oscillators is the result of the combined effects of the PLL loop bandwidth, selectivity of the VCO, and Q of the primary resonator. The quartz resonator (XO) device is operating at the output frequency and does not have the added noise signals of the PLL in the output.

    The higher levels of phase noise demonstrate that MEMS oscillators are not an equivalent technology. Current communications and data transmission applications will very likely have problems with jitter at the levels indicated in the Agilent test system.

    http://www.pletronics.com/getfile.php?id=401

    1. Phase noise and phase jitter
    We considered three frequencies (40MHz, 100MHz and 156.25 MHz) and compared Crystal oscillators to MEMS oscillators of the same frequencies. The Laboratory measurements demonstrate that the phase noise is much better with the Crystal oscillator than the MEMS oscillator for all frequencies.


    http://geyer-electronic.de/fileadmin...Oscillator.pdf

    Anyway, I would like to learn Andreas Koch rationele for using MEMS.

    I just corrected the link. Your first quote is now eight years old, MEMs performance improved a lot since 2009. Anyway the key in the MEMs performance seems to be phase noise due to mechanical susceptibility, an hot subject in WBF.

    IMHO, at this level of performance common technical parameters are usually of little value and should be regarded with great care - theoretically they result in inaudible differences.
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  2. #22
    Site Founder And Administrator Steve Williams's Avatar
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    I have always felt that innocent comments such as that made by Adam can sometimes vilify something. I know nothing about MEMS oscillators let alone other types so his comment piqued my attention.

    Hence my last call to Andreas re Adam's post. His reply......

    "Our oscillators are not PLL based, so this does not apply".
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  3. #23
    Member Sponsor Addicted to Best! Elberoth's Avatar
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    That indeed may be true. I have found this:

    These pMEMS resonators can have a native frequency of up to about 100 MHz. When packaged with a phase-locked loop (PLL) multiplier and synthesizer circuitry, they can deliver almost any frequency from 50 MHz to up to 625 MHz with a frequency accuracy of 50/25 ppm.

    http://beta.electronicdesign.com/com...w.google.pl%2F

    I have no dog in this fight. Just trying to understand the new tech and certain design choices made be Mr. Koch.
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  4. #24
    Site Founder And Administrator Steve Williams's Avatar
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    I don't understand it st all but Andreas said he doesn't use PLL so it doesn't apply to him.
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  5. #25
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    MEMs are NOT 'more accurate' than OSCs as they have higher phase noise, particularly higher close-in phase noise - the result of which is considered to be detrimental to soundstage as it causes a blurring of tones - a frequency modulation effect.

    The one area that MEMs has advantages Vs OSCs is in vibrational susceptibility - OSCs are GENERALLY more susceptible to disturbances from vibrations than SOME MEMs. Methods to shield OSCs from vibrational disturbance can be taken to reduce this susceptibility, however

    Don't know what the auditory perception will be of the interplay of these factors?

    AFAIK, MEMS use a PLL as part of their design - it's within their silicon
    Last edited by jkeny; 04-17-2017 at 06:40 PM.
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  6. #26
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    From here:
    Random vibration induces phase noise at low offsets from the carrier frequency, as shown by the difference between the blue (no vibration) and red (with vibration) curves in Figure 8. Although the ILSI MMD MEMS oscillator exhibits higher close-in phase noise when tested in a quiet environment, adding random vibration does not significantly increase the phase noise. In contrast, both SAW-based devices showed dramatic increase in phase noise under random vibration. This level of degradation can be detrimental to systems sensitive to close-in phase noise and shows how devices in real-world conditions may perform differently from datasheet specifications.
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    Yes, this looks impressive but if you look at the phase noise - the left hand side of the MEMs plot shows phase noise of -40dB @10Hz - a standard oscillator will have about -90dB@10Hz - a good oscillator about -120dB@10Hz. So before vibrational disturbances this MEMS (which is apparently one of the least susceptible to vibrational disturbances) is already 50dB worse than a standard clock & 80dB worse than a good clock - does ordinary vibration from music playback affect oscillators by introducing 50 to 80dB of noise - I doubt it?
    Manufacturer digital products Ciunas.biz
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  7. #27
    Site Founder And Administrator Steve Williams's Avatar
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    I still have to believe that when I asked this very question of Andreas he said his generator does not use PPL and hence not an issue
    Steve Williams
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  8. #28
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    Heard the new Dream DAC prototype at AXPONA today. It reminds me of the 5-series sound, just better. Steve, I think you'll like this DAC.

  9. #29
    Site Founder And Administrator Steve Williams's Avatar
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    Quote Originally Posted by chrisr View Post
    Heard the new Dream DAC prototype at AXPONA today. It reminds me of the 5-series sound, just better. Steve, I think you'll like this DAC.
    Thanks for the update Chris. I've known Andreas for almost 20 years. This DAC really appeals to me as it will do what it is I am seeking. Plus I would say Andreas knows DSD.

    My MPS-5 is back for the upgrade. I should have it back end of this week.
    Steve Williams
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