The well segmented dac-24 bit 384khz thermometer/r2r sign-magnitude discrete dac

Forum Digital line The well segmented dac-24 bit 384khz thermometer/r2r sign-magnitude discrete dac

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    • #1596
      The Well Audio
      Participant

      Since the original thread on diyaudio.com has been deleted the topic is renewed here.

      The DAC Lite is a multibit discrete DAC. The resistor ladder network is segmented, the first 3 MSBs are thermometer decoded while the other 20 LSBs are R2R decoded.
      The DAC implements a sign magnitude architecture to get bipolar output, so there are 2 x 23 bit ladder for each channel, one for the positive rail and one for the negative rail.
      The dirty signals like bit clock and data are optically isolated to avoid any interference with the latch signal wich drives the DAC switches.
      The bit clock is stopped as soon as data have been loaded into the shift registers, so every time the DAC switches to a new word the bit clock cannot affect the latch.
      It uses a custom protocol provided by the TWSAFB-LT FIFO Lite.
      The FIFO Lite also provides a digital calibration for the DAC Lite in order to compensate the error due to the resistors tollerance used in the ladder.
      It’s a voltage output DAC which provides 1.1V to 1.8V rms depending on the Vref power supply, from 3V3 to 5V. The output impedance is 625 ohm, so the DAC can drive directly most amplifiers.
      There is an optional buffer if the load wich has to be driven is lower than 20K.

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    • #1605
      Crom
      Participant

      Congratulations Andrea – looking forward to some interesting discussion.

    • #1608
      jmmbarco
      Participant

      Hi Andrea!. Hope we can finally get useful info for our projects without trolling!

    • #1611
      Ilgavro
      Participant

      Hi Andrea!. Hope we can finally get useful info for our projects without trolling!

      Exact! Maybe here we learn something!

    • #1614
      Ivan
      Participant

      Hi guys. Excellent news! Congratulations.

    • #1690
      pinnocchio
      Participant

      Yes, on DIYaudio it was a total nonsense about trolling. We can finally get details here without issues!

    • #1693
      pearse
      Participant

      DAC Lite continuing to delight here, I went through a period where the sound was not as good but I had been experimenting with cables and power supplies.

      After any change it needs several days to settle down it seems in my system.

      I added a 3 channel Paul Hynes SR7 power supply to the front end SD playback units and added a Musetec USB100 Interface on channel 2 of the Fifo recently.

      I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.

       

      I plan on finally transferring the build into a case in the coming weeks now that I am happy with all the tweaking.

    • #1697
      minionas
      Participant
      pearse Said

      I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.

       

      Hi,

      What it brought to your system? Im wondering about its transparency (if details or resolution are a bit lost) and its “tubiness” (if it add any tube goodness?

    • #1699
      pearse
      Participant
      pearse Said

      I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.

       

      Hi,

      What it brought to your system? Im wondering about its transparency (if details or resolution are a bit lost) and its “tubiness” (if it add any tube goodness?

      Hiya,

      No loss in detail or resolution and it has taken over a week to settle in.

      What I am hearing now is a little more weight and authority on bottom end and highs are a little sweeter without any loss of detail, you could say a little tubey on the highs.

      Listening to Steely Dan, Two Against Nature at the moment and it sounds amazing.

    • #1728
      Sebastian
      Participant

      Hi Andrea, I have a question regarding Vref and the DAC’s output (1.1-1.8Vrms).  Is there an ideal voltage for Vref (best sound, lowest distortion, etc)?  I ask, because I am able to accommodate for variance with my preamp, and now that I am planning, it would be helpful to know that. I won’t be using the buffer, as the input impedance of the preamp is high.

       

       

    • #1733
      The Well Audio
      Participant

      Hi Andrea, I have a question regarding Vref and the DAC’s output (1.1-1.8Vrms).  Is there an ideal voltage for Vref (best sound, lowest distortion, etc)?  I ask, because I am able to accommodate for variance with my preamp, and now that I am planning, it would be helpful to know that. I won’t be using the buffer, as the input impedance of the preamp is high.

       

       

      We have used 4V and 4V7, and in our opinion there wasn’t any SQ difference.
      We have powered the DAC Lite with batteries, but it looks like someone preferes shunt regulators.

      We will test shunt regulators in the next listening session.

    • #1741
      pearse
      Participant

      I added 2 x 500F paralleled supercapacitors (1.6-7v in each Cap) on each of the 3.3v Vref supplies and I found a very nice improvement in low to mids body and presence in my system. I also added pairs of supercapacitors on the VDD lines but did not hear any change in sound with these in place.

      Spent some time sorting Caps to find pairs that charged and discharged evenly and so far so good with balance maintained in pairs. I never shut down power so no worries about startup but I have disconnects in place in case I ever need to shutdown and recharge the Caps on startup.

      Will monitor Caps voltages over the coming weeks to see if I need to add balancing resistors.

    • #1742
      pearse
      Participant
      pearse Said

      2 x 500F paralleled supercapacitors (1.6-7v in each Cap) on each of the 3.3v Vref supplies

      The above did not make sense 🙁

      (2 x 500F series set) in parallel on each of the 3.3v Vref supplies.

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