Hello Doede,
At first thank to you for your free giving of all the information's about the DDDAC1543. It is very helpfully for me and I think for some DIY freaks too. And too it is nice that you offer the PCB's and I saw last on your page that you now offer too part-kits. I build the DDDAC1543 and before I heard the item I measured some signals with an oscilloscope. I can't later believe what I heard, better what I doesn't heard, when I remember on the wave with the sampling frequency on the screen. I asked me why I have bought some month's ago the SONY SACD XB940? I was surprised especially about the clarity of bass-instruments and much more.
I heard with a headphone AKG K1000 and a self-build WCF-tube amp specially designed for that headphone. I hear more classical music in the evening. I cooled the DAC-tower with a fan so you described that. But because the AKG K1000 is an absolutely open headphone I wasn't amused of the "sound" of the fan. It is a 12 volt fan and runs with 5 Volt so you recommended. But you will hear much more in the night when the other sleeping. So I decide to build a heat sink-tower. It is described down with pictures they say more as a lot of words I think so. Here is the cad-file of the part: Tower Cooler ver. 2.   This works with the Schaeffer CAD Software. Can be downloaded for FREE :-)
Bye and thanks
Ralf
I have the idea to insert between each DAC one heat sink and stable them in the same manner as the DAC's. I looked for the place I will have. O.K. the wire-bridge and the resister must shift to the down-side of the pcb, but that's not a problem. But made such small aluminum part by me self?? Never, that's not my matter. So I remember me for Schaeffer Apparatebau they made already some excellent milled parts for me.
But so small parts and how are the costs?? O.K. all sinks in one part and I will separate they by myself. This is able to do for me too! You see already my lines where I will saw the part (with a common fretsaw). The pictures down show how the DAC will later positioning. The deep for the DAC's is 3 mm. The height of the DAC body is given in the data sheet with 3.2 mm. Enough to clamp the DAC's. But in my case I must grinding only a touch of the aluminum-parts (above) so that the DAC-body will be a touch higher as the deepening in the aluminum. It is maybe also possible that you must grinding a little bit (smooth with sandpaper) the surface of the DAC's. Hey that's in this case "real High End" (You know some High End producer grinding the name of the (common??) parts ;;-).
The soldering is after the positioning of the DAC's between much easier! I used a 2.5 mm thread-rod and forgot in my milled part the thread in the first sink. So I must later glue the rod in the first heat-sink. It is already changed in the cad-file. So now it is possible to screw the rod in the first part and stable they others. On the top I used a heat sink I have had in my box. Put between each surface a little bit of a thermo lube, but without any silver or so. Don't forget a hole in the top-plate for the bias-current-pot.