I have gathered together the schematics for the non oversampling TDA1545 DAC. Mind that I am only responsible for the shunt regulators, the microcontroller, and the input selector. The digital input circuitry was developed after reading some post from Jocko Homo on the diyhifi.org forum. The TDA1545 circuit is mostly from the Philips data sheet. The I/V stage is from rbroer on DIYAudio.

At some point in time I have made the following block diagram, and from memory it seems correct.

From the top here is the input selector board, the micro controller for the relays are on a second board, as per the block diagram.

After the relays, comes the SPDIF buffer/amplifier circuit based on Jocko Homo's. The CS8412 converts the SPDIF signal into the correct I2S format, I2S data goes both to the DAC board, and the micro controller board. The micro controller signal is buffered by one of the 7404 inverters, in the hopes that any noise from the micro controller, will be isolated.

The shunt regulators, are duplicates of the similar valued ones in the shunt regulator schematic, you do not need to build these twice!

Here is the DAC circuit.

Everything is in the puzzling Philips data sheet. The relay shuts off the data, while the micro controller scan through the inputs.

Here comes the shunt regulators

The one at the bottom is the one for the DAC, and the one that is not duplicated on the input selector board.

Here comes the I/V from rbroer, which is fed from the unregulated DC supply.

And the micro controller schematic.

I have redesigned the PCB layout's without saving the ones I used in the working DAC. Therefore they have not been tested, and I would rather not publish them, and have them blow up in some poor persons face.

There was an error in the last PCB posted, here comes the correct version.

TDA1545 NONOS DAC II Rev. B Cadsoft eagle project files

I have just assembled and tested the prototype shunt regulator for the DAC. Inpsite of long wires and veroboard it performs a little better than the LM317+CSS+diode shunt I've been using so far. When they arrive I will try replacing the transistors with some low noise BC560 types, to see if they perform better.


The peaks at 50Hz, 100Hz and so forth comes from the SPDIF -> I2S converter board, where the PSU has not yet been optimized.


TDA1545 NONOS DAC II Cadsoft eagle project files

Generated on 2018-05-03 01:14:21.900342