Discrete R2R DAC for Raspberry Pi

Yes, I was minding my own business when Mr Ew dropped me a message, “would you like to try my new toy?” “What toy?”…

I was shocked when he sent me the photo!

Few days later, I received this Discrete R2R DAC for Raspberry Pi along with a regulated 5V @3A supply. How nice is that?

I can’t believe how Ew managed to fit everything into this small board. Hey, this is a 24 bit DAC so there are 48 resistors per channel. (No sicko enjoys soldering this bitch!). Before we even get to soldering, these resistors need to be hand matched as resistor tolerance could cause significant distortion. (No sicko enjoys matching these tiny resistors!) The heart of signal processing is handled by the huge FPGA chip.

For comparison, here’s the Final Discrete Monica I built years ago.

Zoomed in just on the main board and you can see USB input via the Amanero, of which signal is fed to a huge FPGA module (underneath this PCB) where signal processing is done. Back then I had to learn how to code in VHDL in order to program the FPGA. Hey, programming is part of my day job but the coding sequence is sequential but with VHDL/FPGA it is in parallel. This messes up our thinking.

Sequential : Wake up -> Brush teeth -> Walk the dog -> Make coffee…

Parallel : Wake up AND Brush teeth AND Walk the dog AND Make coffee…

Err, how does this happen? Well, we human beings are not great at multi-tasking (despite what the fairer sex says). But machines can accomplish this. Telling the machine how to do this… can mess up our thinking.

Look at me! I have not been the same since I programmed VHDL/FPGA!

Okay, after digital signal processing, music signal is then fed to 4 clocked buffers and the ladder R2R resistors (hand matched as well). Also, i went nuts with shunt regulated supplies on almost every stage… Also, I went nuts stripping off sleevings off the electrolytic caps (this makes a difference so much so my deaf ears could hear it).

Needless to say, building the above was a back-breaking, eye-numbing, solder fumed fest. It was anything but pleasant. I was a self flaggellating fetish back then.

Okay, enough!

And then Mr Ew comes up with this cute little package! And he programmed the FPGA as well! Damn!

Assembled below with the power supply. My itchy hands have to solder in an extra 2200uF…

Man, I was still enjoying the AD1865 Raspberry DAC when I received this new baby.

And all I could say is…. It’s GLORIOUS!

There is difference in musical presentation between the AD1865 and this Discrete puppy. I prefer this Discrete DAC as music seems to be more “alive”. It’s probably a bit more forward too, but not that irritating in-your-face sense. More forward compared to the AD1865.

It has that… je ne sais quoi… that some girls have that make you fall head over heels over them. Sure there are prettier girls. Sure there are smarter ones (or if you prefer dumber ones). Sure there are more engaging company but… She has that je ne sais quoi and you keep returning to her.

Geez…. why did I bother building DACs when we could have Mr Ew build better ones?!

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