Brief
DIYAudio thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=108571
PCM bits can be converted to current source or sink.
Accumulation by Current value can make "Full Digital PowerDAC".
This is not only a DAC, it can drive Speaker. so this is integrated full digital amplifier.
There are no analog components. every module only handles PCM Bit
signal, then only a "wire" will accumulate all currents.
One
Bit principle
Schematic
- PCM Data is converted to +(0000 7FFF)(Current Sourse),
-(0000 7FFF)(Current Sink)
- Voltage Reference works as Volume Control
- Analog switch for Voltage Reference, driven by each data bit
- Pre LPF after analog switch for each bit
- Digital to Current Conversion, refered to GND
- Level shift to Vsupply or -Vsupply
- Output is accumulation of all currents
sch.pdf
PCB
- 12x12 inches
- most left: Left D7 to D0 Current source / sink
- 2nd left: Left D14 to D8 Current source / sink
- (right side as same)
- Powers: for OpAmps, Transisters, 5V
- DAI / Serial-Parralel / conversion for + and - / AVR /
Voltage reference
- 100xOpamp, 400x0.1uF, 600 resistors, 60 analog switch, etc.
Making
3 bits are implemented.
Now triangle wave is converted to current waveform, 0 to 7 step for
positive / negative.
whole connection.
Measurement
0.3% THD is not so bad as first prototype.
improvement for more accuracy can achieve better performance.
still musical enough. good at presentation of stage depth.
Summary
The soldering will make you crazy, but you can hear..
- full digital
- no PWM conversion
- no Noize-Shaper
- no LPF on output
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