Soekris DAC Build

[Ray P]

Almost ready for a listen!

I've done most of the remaining assembly today and now have to wait for some PCBs to be delivered so I can interface the Soekris R2R DAC to the USB input board. Just final hook-up and a few bits of tidying up to do.

[Dave the bass]

Schweeet.

Ooops, I mean shoddy.

Neat work MrP.

[IslandPink]

That is really nice - top notch !
What are the valves, are they the outputs ?

[Ray P]

Thanks chaps.

Mark, the valves are 6SN7s in Broskie Aikido confoguration.

[Ray P]

The PCBs I've been waiting for have arrived so I'll make one up tomorrow and, all being well, the Soekris DAC will spring into life!

[JohnG]

Can't wait to hear your initial views Ray. These models are very well liked.
How does your build differ from the Standard Assembled ones now available from Soekris ?

[Ray P]

How does your build differ from the Standard Assembled ones now available from Soekris ?

Apart from using a valve-based output buffer I also have better power supplies for the Soekris.

[Ray P]

This project has been a bit slow of late as I am experiencing a loud buzzing from the Soekris DAC board. I'm working through trying to isolate the problem but it seems to be a fault with the output stage. I'll hopefully get this resolved so I can get this DAC working properly as I want to be able to compare it with the DSD decoder project that I've just posted about.

[Ray P]

I've left this project on the shelf for quite a while because I've been rather taken by the DSD decoder project but, being off work has resulted in boredom setting in, so I've invested a little time on resolving the issue with this project and I tracked down a grounding issue. The result is that the Soekris DAC module is now making music with my test system. Positive first impressions but the test system isn't good enough to draw any real conclusions so I'll move it into the main system for a listen later.

[Ray P]

Had a very quick listen (sans Broskie ACF-2 buffer) on the main system and it sounds very nice - should improve with burn-in.

Before that though, as I have two decoder projects on the go (this one and the DSD project) I decided it would make more sense to take the buffer stage out of this project and house it seperately, so it can be used with either decoder. So, I've removed the Broskie ACF-2 buffer and transformer and just have to rearrange the power supplies and add new power transformers before I can get it back into business properly.

[Thermionic Idler]

Sorry for the thread archaeology but thanks to Ray for the heads-up on these DACS and the associated power supplies etc. I now have a cunning plan for a music server based on this DAC - basically a NUC running Daphile (the subject of another thread) plus the Soekris DAC, going in to a pair of AMB alpha 24 linestage boards that I used in the Dieselpunk preamp, configured as a DAC output stage. I'll probably start a separate thread when that gets going.

[Ray P]

Hi Dave, for info my Soekris DAC is finding a new home (and is currently out of service); I've started to build it into a headphone amp based on the Transcendent Masterpiece pre-amp. It's very much a back-burner project though as my focus has been on the 13E1 build and then I'll move on to finishing my DSD decoder project.

Which Soekris board (or boards if you go the differential route) are you going for? There have been some new releases;

http://www.soekris.dk/dam1941.html

My board is the 1121;

http://www.soekris.dk/dam1121.html

[Thermionic Idler]

Hi Ray, probably the 1121 too as it seems most optimised - the 1941 and 1021 has stuff on that I don't really need.

This really follows on from my discovery of the Daphile software - everything just fell into place after that. So what I want to do is design and build a full music server into a case the same dimensions as the preamp I just built. So Intel NUC Atom > I2S-USB > DAC > AMB output stage (no way I'll be able to fit a valve output stage in there). Also with a TOSLink SPDIF input which we can run the TV into.

Those power supply boards from Australia look very interesting, it seems that they have a little less noise on their output than the AMB ones I used for my preamp, yet take up less real estate. Actually if you have the dimensions of those boards that would be really helpful!

AMB configures the output buffer to have a 100KHz 3rd order Bessel low-pass filter when used as a DAC output stage - I know from reading the Soekris documentation that ultrasonic noise needs filtering out on normal DACs, question is whether it's needed for this one - I'm guessing it would be wise to still include it so as not to risk upsetting anything further down the line (the preamp runs wide open to 1Mhz I think).

[Thermionic Idler]

That said, if I put the NUC into a separate case (might not be a bad idea anyway) that opens up the possibility of configuring the dam1941 with a balanced tube output stage. Also, looks like no USB to I2S conversion is needed.

[Ray P]

That said, if I put the NUC into a separate case...

That's what I would do, gives you much more flexibility.