AD1865 based audio DAC with I2S input and voltage output


Posted on Feb 5, 2014

Circuit AD1865 is considered like best 18bit stereo audio DAC ever. I already built another DAC, that I will not say everything again. However I found, that current output is too weak and instead of using external I/V converter I used this, what is included in DAC. Because DAC doesn`t have buffer for data, that both channels was not on the output


AD1865 based audio DAC with I2S input and voltage output
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simultaneously, but alternately left and right channel. This can produce theoretically hearable phase-shift. Last I want to connect DAC to USB receiver with only I2S data output. All troubles solve following circuit. Supplying need two separated windings on power transformer, because I used positive voltage regulator for negative supply branch. After rectifiers B1 and B2 are filter capacitors C1 and C2 and behind them group of block capacitors. I used available low-drop voltage regulators LE50. One is for supplying of digital part and two are for positive and negative analog part of dac. Closely to regulators and integrated circuits are small filter and blocking capacitors. DAC doesn`t have I2S input, which is usual. It has individual data inputs for left and right channel and individual "latch" inputs which rewrites data from internal register to DAC output. Input data in I2S format (left justified) are first delayed for 13 bits thus that after shifting of 18 most significant bits to the dac register they will be written to output. For simultaneous playing of left and right channel we must delay data of left channel for 32 clocks (frame lenght for one channel). Result is that data for left and right channel are shifted together to the dac and they are written to the output with common latch signal. Because there doesn`t exists 32bit shift-register I had two choices. Create them with help of Xilinx, but I have not...




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