I had the idea to make a "tube DAC", simply as an exercise to see if it could be done. I've seen a few designs that seem to achieve this. I also saw somewhere that R2R DACs can be implemented entirely with resistors, not requiring any active components? I'm making this thread to clarify my assumptions and what possibilities there actually are. Practicality and distortion are not specifically priorities here; while I may not proceed to build an impractical, high-distortion design, I am interested in knowing it exists.
The Americans used digital voice encryption in the Second World War, so of course it's possible.
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I knew someone had started a thread about this before, but didn't remember it was you:
https://www.diyaudio.com/community/...-and-discrete-components.382932/#post-6936901
https://www.diyaudio.com/community/...-and-discrete-components.382932/#post-6936901
In 1987 there was a sound card that plugged into your pc's printer port, and all it was, was an 8bit R2R with no real IC's (ok, a FIFO 🙂 ), just a bunch of resistors in a ladder (look up Covox Speech Thing). People made their own and it was quite cheap and good considering what came with your pc stock.
For 8 bits only and things like games and such you can get away with that approach, but for hi-fi to get any more bits requires increasingly tighter and tighter matching between resistors, to the point where some other techniques have to get involved (dynamic element matching, data weighted average, etc..), in addition to laser precision trimming the actual resistor traces on the IC, we are talking micrometer if not nanometer levels of precision here. And even then, you would be lucky to have linearity to 16 bits.
For 8 bits only and things like games and such you can get away with that approach, but for hi-fi to get any more bits requires increasingly tighter and tighter matching between resistors, to the point where some other techniques have to get involved (dynamic element matching, data weighted average, etc..), in addition to laser precision trimming the actual resistor traces on the IC, we are talking micrometer if not nanometer levels of precision here. And even then, you would be lucky to have linearity to 16 bits.
Hey, look at that! I had forgotten about that post (I even did search for similar topics!). Thank you
