Lyrebird

True24 DAC
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This is still a concept site. It will be updated in parallel with the project progress.

The goal of the project is:

I want to create a new digital DAC sound card solution, even better as the T-DAC, RPi-DAC

It should be able to reproduce any sound and song I want to listen to, in the best achievable manner, even like a Lyrebird.

  • create a True24 bit DAC which can really provide a 24bit resolution
  • keep a modular concept so that it can be customized for interface, resolution, costs ...
  • use an FPGA in order to feed the DACs, with filtering, control, synchronisation ...
  • it results in supporting a real 144dB SNR figure and to consider the noise on all components

There are two approaches to achieve the goal:

Approach 1 Approach 2

DualMono and many DAC modules as needed

  • use PCM1794 DAC in DualMono mode
  • use so many DACs so that we can gain +3dB for every DAC added
  • it might result in using 5 DACs per channel, in total 10

2x 16bit High Voltage DAC with analog signal combination

  • use high voltage DACs in order to keep the output signal away from noise
  • combine two 16bits and add the output voltage in a way that a 24bit digital value is converted

Pros

  • the same DAC module can be used, highly customizable, e.g. different resolution (costs)
  • native support of 192KHz sample rate
  • well proven concept, e.g. RPi-DAC DualMono

Pros

  • less modules needed, potentially an even higher bit resolution is possible (EOB), e.g. 28bit
  • working as a Non-OverSampling (NOS) DAC
  • easier to keep the output signal away from the noise (high voltage)
  • less modules needed, smaller and more cost-effective
  • DAC might be more linear, less DAC errors, possible to skip faulty LSBs

Cons

  • much more modules and components (costs) needed
  • still an oversampling, delta-sigma DAC (even FPGA could help)

Cons

  • needs justification (trim), high quality (low tolerance) circuits (e.g. the voltage divider), e.g. use 0.01% R
  • might support up to 96KHz sample rate, not 192KHz or higher (but OK)
  • effort to convert I2S to SPI and to sync the DACs (FPGA, micro-controller)