leo
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Post by leo on Sept 28, 2007 14:02:17 GMT
Having another play about with one of my dacs mainly the PCM1794 based one I was looking at this output stage home.quicknet.nl/qn/prive/ra.vdsteen/pdfs/CD_outputstage_PCB.pdf I was thinking of trying it with the dac, The PCM1794 has +/- current output, in the one I have here it uses passive I/V resistors that goes into a op-amp which do differential to single ended conversion and apply gain I was going to build that discrete stage but miss off all the filtering on the inputs as its no needed with the PCM1794. Any comments on the circuit? rather than using J-fets I may use transistors, also I won't be using Bg caps ;D if it turned out ok could always improve the regulation after
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Post by gns on Sept 28, 2007 19:19:39 GMT
Interesting, although I understand little of DACs. Is this supposed to actively filter out the "crap" through looking at the difference between the two inputs?
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Deleted
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Post by Deleted on Sept 28, 2007 21:43:03 GMT
Leo What do you know about the PCM1796 ? Asus is using this in their new soundcard, the XONAR D2.It's 192KHZ 24 bits, and has been measured by PCUser at 122.5dB SNR and .0006% THD at 1KHZ Crosstalk was 115.4dB and IMD .0006 % Alex
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leo
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Post by leo on Sept 29, 2007 0:52:55 GMT
Interesting, although I understand little of DACs. Is this supposed to actively filter out the "crap" through looking at the difference between the two inputs? Yes, also really need an active gainstage because using passive current to voltage conversion the output is still only quite low so needs boosting up. Nice thing with these dacs is that you can easily go balanced out or single ended. Most common is differential to single ended using an op-amp so it gives no DC offset
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leo
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Post by leo on Sept 29, 2007 0:54:21 GMT
Leo What do you know about the PCM1796 ? Asus is using this in their new soundcard, the XONAR D2.It's 192KHZ 24 bits, and has been measured by PCUser at 122.5dB SNR and .0006% THD at 1KHZ Crosstalk was 115.4dB and IMD .0006 % Alex I don't know much about the 1796, I think its harder than the 1794/8 to implement because it needs to be used with a micro-controller for internal register configuration that needs programing but if its already all implemented it should be an interesting one to try out especially in something like a soundcard. The PCM1790 family are quite decent dacs, I like the 94 best mainly for its higher output so can use lower value I/V resistors
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Post by minivan on Sept 29, 2007 23:54:45 GMT
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