Open Hardware 1-bit multi-level DAC
by, 04-17-2014 at 07:09 PM (3543 Views)
In response to endless DSD arguments here at CA I promised to publish an open hardware design of 1-bit multi-level DAC without magical black boxes. No DAC chips. No camel-back DSD ultrasonic noise bumps either, even with 7th order modulators. Multi-level, but still 1-bit. How is that possible? Well, it's not a secret and I wanted to put it out in an open way. A DAC that is not trying to play dual-role between it's PCM-to-SDM and DSD.
Moving most of the DSP things to software, having only minimal amount of digital logic in hardware and all visible at a glance on schematics. It was supposed to be as simple as possible but not any simpler.
I decided to use Amanero Combo384 USB interface as plug-on daughter card for interfacing purposes because it is nicely available and supports the needed DSD rates up to 24.576 MHz.
This version is by no means final, it is first version of what I came up within a month (simplified from my earlier protos). I will make updates to the design to improve it. And yes, I know, there are many ways to improve this further. This one was intended to be minimal "discrete" implementation without programmable logic or anything. Minimizing board space, number of layers (just two), minimal SMDs, minimal number of components that are easy to obtain, and low cost. But still decent performance.
Since it is an open hardware design, improvement suggestions and contributions are welcome. :)
Enough of excuses and disclaimers... This is how rev.A boards look like:
Direct 1-bit, 33-level conveter.
And here you can find the most up-to-date design documents.
P.S. And maybe there'll be DSC2 with all the imaginable high-end bells and whistles, but still no black boxes. ;)