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  1. W

    SOTA Pyxi Phono Stage Review

    No it would not, unless a DC-DC conversion is done to generate the +/-15v rails, or +/-18 or so volts are supplied- as was the case with the Acrux, and that requires a separate case and umbilical. I think the low voltage ac source works well for low current circuits- as was shown in the Pyxi...
  2. W

    "We need to move on and use distortion measurements that are perceptually meaningful."

    Yes, but careful design of the implementation of the pole-zero constellation, the use of very high and frequency independent levels of negative feedback, the use of highly linear caps and resistors and control of load impedances makes it doable, even for LOMC use.
  3. W

    "We need to move on and use distortion measurements that are perceptually meaningful."

    Yes. It emphasizes the need to have much lower higher order (for example, ninth) distortion products overall. This is not due solely to the non-linearity inherent in the input stages, but also the action of feedback and the presence of level and load dependent non-linearities in the output...
  4. W

    "We need to move on and use distortion measurements that are perceptually meaningful."

    Virtins Pro includes the GedLee metric as part of its test suite. I use it, and a 21 tone 20-40kHz c. 1/f weighted stimulus with the peak set to the RMS "nominal" output level plus 3dB to test phono preamplifiers. The tones are spaced to produce non overlapping intermodulation products and the...
  5. W

    SOTA Pyxi Phono Stage Review

    Still no ground problems... Oddly enough, jjmanda and I are the only two to have experienced, or at least reported, the issue. The fix will be incorporated permanently into the board of future builds and I have a modded unit. The issue was discovered post release.
  6. W

    SOTA Pyxi Phono Stage Review

    It does, service is generally excellent, but they're just a tad busy at the moment- lots of irons in the fire don't you know. Whether you hear from them or not you should start a conversation with me, as that's more or less how it works with any of the more "difficult" situations. They have had...
  7. W

    SOTA Pyxi Phono Stage Review

    Well, you are the amongst the few in what, 400+ units that use this approach. You'd probably be better off communicating with me directly to explore the issue, as ultimately that's what SoTa will do, and if it can't be resolved then return the unit. Let SoTa know that you are doing this. If you...
  8. W

    SOTA Pyxi Phono Stage Review

    I have an ex-associate at ADI who sent me a link to an article on ADI "seismic sensors", having read the Pyxi review. I think it is of interest. Perhaps others agree, in particular the section on "geophones"...
  9. W

    SOTA Pyxi Phono Stage Review

    Well, the idea was to produce a technically excellent design, using the anti-audiophile design approaches that were originally posited. The specific goals were an extremely compliant RIAA response and extremely low HF distortion, below -110dBc at the units rated output, and excellent, indeed...
  10. W

    SOTA Pyxi Phono Stage Review

    Not exactly the same thing. Your approach sums the LF mono and stereo signals to produce a composite mono signal and applies that to both channels. i.e. 2LOUTLP=2ROUTLP = LINLP+RINLP. The warp approach does not sum the two channels but takes the ordered low pass difference of the two channels...
  11. W

    SOTA Pyxi Phono Stage Review

    The next model has already been designed. In fact two different models- a MM only unit (PyxiMM?) with switchable 35/45dB gains and MOSFET inputs, the Acrux with, well, pretty well everything better (distortion, noise, power supply rejection etc.) and true MM/MC separate channels and 2dB gain...
  12. W

    SOTA Pyxi Phono Stage Review

    The warp filter does precisely what you suggest, but in an extremely controlled and non audible way. Please read the whitepaper that was introduced earlier.
  13. W

    SOTA Pyxi Phono Stage Review

    To add context. Part of the way I started down this path was I was using the RME box to digitize various LPs. I followed the same strict procedure as is my wont and normalized all the recordings to 1dB below FS. This was in the early days of the DIY stage development- three or four years ago if...
  14. W

    SOTA Pyxi Phono Stage Review

    Answering this is going to sound like an ad for SoTa. Having said that, they choose to demonstrate their turntables at audio shows and audio society meetings/demos with the production Pyxi and the Acrux prototype, they have been extremely pleased with the comparative listening sessions, and...
  15. W

    SOTA Pyxi Phono Stage Review

    Correct, but the "resonant frequency" (see my prior post) is generally substantially sub 20Hz, and LPs have demonstrated LF modulation (explicitly lateral in almost all cases) no lower than 20Hz, and in my experience, no lower than 24Hz, and some claim even higher than that. Oh, and the way the...
  16. W

    SOTA Pyxi Phono Stage Review

    The DC feedback loop bandwidth depends on the mode MM or MC as the forward loop gain is stepped by 20dB (the loop feedback occurs from the output of the final gain block) It can be c. 1.4 or 0.14Hz, if I remember correctly. That's what caused me to have to "optimize" the phase compensation for...
  17. W

    SOTA Pyxi Phono Stage Review

    The architecture is identical, save the presence of the warp filter. It is the ability of the warp filter to essentially remove the bass excursions that lends credence to the idea that the extraneous modulation is effectively almost entirely warp driven, and that the explanatory aspect of the...
  18. W

    SOTA Pyxi Phono Stage Review

    Please read the posts from Korf. The PU/cartridge "resonance" when combined with the differentiation of the cartridge action translates to a high pass of variable Q and frequency. This transfer function is "excited" by the various modes of the imperfections of TT and LP and the result appears...
  19. W

    SOTA Pyxi Phono Stage Review

    No. That is not the case. I did this to test an hypothesis concerning what makes an audio device that uses negative feedback acoustically acceptable or not. Read the white paper posted before. It's necessarily simplistic- it is intended for general consumption- but it makes the point adequately...
  20. W

    SOTA Pyxi Phono Stage Review

    http://korfaudio.com/blog67 http://korfaudio.com/blog68 http://korfaudio.com/blog69 http://korfaudio.com/blog70 For those of you who are really interested in the LF resonant behavior, the above blog entries (all supported by actual measurements using accelerometers etc. as well as cartridge...
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