Plot (21/10/2013):
Okay, i need a DAC. For a car. Thus the requirements are:
- Small footprint. I don't want to build a monster like these vintage beasts.
- With good jitter immunity (going to use it with jittery TosLink mp3 player)
- The less power supplies the better, as i need 'em isolated
- Single 12v power supply input - car battery.
So, the chices are... E$9023.
Huh, only one? Why?
- Dedicated ASRCs are pricey. ES has one on board, for CHEAP.
- Output stage. No need for dedicated I/V + LPF. CHEAP. Small footprint.
- No need for extra negative supply.
SPDIF receiver? For a good source, the jitter performance of DIR9001 and WM8804 are quite close, but when we add some HF jitter in there, WM8804 part wins. Built-in comparator input, double PLL and other nice features...
Clock? I'm LAZY. With ES ASRC you can use almst any clock for it's MCLK input, as long as it's greater than 256Fs or something like that.
50meg, 30meg, anything.
Hey ya, how about these cute SC-cut OCXO bricks from telcom equipment? Cheap, low phase noise...
Power supply section.
I'm going to use MeanWell DC-DC brick, with 12v input, 24v output, 5W. 24v is kinda too high, but that's all i've got in the drawer. And they are isolated.
24v thing could be employed in some shunt-stle regulation, with current sources and paralel TL431 regulators. Cheap, easy, small footprint, good infinity approximation with 24v.
May run hot... needs some power calculations.
V0 (22/10/2013):
Schematics
V1 (24/10/2013):
Looky at that S/PDIF input! :)
V2 (26/10/2013):
Almost there...
V3 (28/10/2013):
Change of plans... Lynx (
http://www.????.???/ (link was removed due to facist propaganda)) did it better.
The capacitive loading of DAC's output worrified me a bit... yet if everyone goes this way, why meh be different? i thought... *walk this way* they said.
So... /me going active output stage without any significant increment of components count/no board size increment... By reusing ES's charge pump's negative output. Bravo! Ce'st magnifique!
Beefier caps on the NEG and VREG(REF) pins... I've tried to fit these, but my 8mm caps won't go... 5mm dia did the trick.
V4 (03/11/2013):
Ehm... Kinda... call it final design review. I have doubts in the creepy DC-DC converter i choose... Given the every part of the schematics is top notch... and throwing in such a bad DC supply could ruin all the effort i've made...
Schematics V4
