Vermes
Advanced Member level 4
It is a construction of digital-analog converter made of CS8416, PCM2704 and TDA1543.
CS8416 is a SPDIF receiver which has built in 1 of 4 inputs selector. All inputs are used in presented here system: two as coaxial inputs, one optical with TORX147 receiver and one used for USB input. CS8416 can operate in two modes. In this project it is hardware mode. You can select one of two output formats of CS (TDA1543 accepts input format I2S and TDA1543A – format EIAJ) by corresponding resistors.
PCM2704 was used to gain USB input in the device. Although the PCM has a SPDIF output, you do not need to use its built in DAC, but connect its digital output with input selector of the CS system. The PCM is powered from USB port of a computer, so, in order to separate it from the rest of the system, connect its output with CS input through the transformer. In two coaxial inputs you can select option from manufacturer's note of the CS, without transformers.
Current-voltage issue was solved by active discrete system – **broken link removed**. You have to find a new value of the resistor in the current source, when instead of BF245A you use another current source, for example on BF245B. The current source must produce the same current. In addition to the system, there is a low-pass filter, which suppresses the over-acoustic frequencies.
Due to the fact, that the other components of the systems are remote controlled, the DAC is equipped with simple control system on a small microcontroller AT89C2051. That system implements on/off function, changes the input and receives remote control signal in RC5 format.
Power supply based on processed transformer TS8/38 supplies the device. That TS has triple secondary windings connected together. When you add two pins to disconnect them, you receive a transformer with three independent secondary windindgs. Two of approximately 8V, one to supply the control, and another switched by control for CS and TDA supply. Winding which provides voltage of about 16V to supply the I/V converter and low-pass filters can be switched by control system.
The system was closed in housing from a broken AS-254. As a standard, that housing has 70mm, but it is better to cut it to 50mm. Aluminum sheet was glued and screwed to the cut front panel. Remember to make holes and glue descriptions made on self-adhesive tape. Then varnish the front panel with a transparent lacquer.
If you want, you can also process the remote control so it fits the rest.
Final effect:
Link to original thread - **broken link removed**