NOT QUITE NEVER AGAIN, THE GROUP BUY DAC BUILD

[nige2000]

In the words of Britney Spears "ooops i did it again"

Yes another group build

http://www.dddac.com/dddac1794_design.html
https://www.diyaudio.com/forums/digital ... input.html

A few years ago I bought a dddac1794 kit as an upgrade to a cuinas dac,
to my surprise it wasn't, although it did have some nice qualities
So i was faced with either flipping it or mutilate it with a modding project rendering it worthless
............ yea... its a kind of disease i know..

once id made the first power supply lifepo4 modifications which had very promising results i contacted John Kenny and said i thought it had potential to better the cuinas by quite a margin with a bit more work.
And John pointed me in the right direction on many points notably current reference on pin 20
also the community on the dddac thread at diyaudio that helped develop those ideas over the next couple years,
and Encrico which i collaborated with in this revision of his own version of dddac 1794

What is this dac

it is a dual mono burr brown pcm1794 chip (one chip per channel)
No digital filter
with synchronous reclocking of audio signals (bck, lrclock and data) just before dac chips
Potatosemi logic were possible

some early prototype pics

[nige2000]

this revision
is shaping up





several errors to fix from the reflow oven but we will get there
and we will clean them off with some acetone before final assembly

been a bit rusty and with Pearse and Tony it took most of the day to get this far (i haven't looked at this design for several months)
id be hopeful we would get the rest of the boards finished next meet up
then set up two dac boards to a-b test different power solutions lt3045, supercap, and lifepo4 and then decide which were going with.
think were going with two i2s inputs the diyinhk xmos usb to i2s and the sd card player (as seen in other thread)for best flexibility





im hopeful these dacs will be up there in sound quality with the top few we have heard
there is s few output stage options we can explore at a later stage if we decide to do so

[randytsuch]

Cool project Nige

Guess I'll be following from afar again.

I'll assume you like this better than a soekris otherwise there would be no point

Randy

[nige2000]

The last prototype I built was marginally behind the heavily modded soekris.
This revision has to be better as we will have better power solutions and we had an ordinary 574 chip reclocking previous now with the potato 374

I don't know what will be better just yet,
its certainly will be at the races

My gut feeling is that in certain areas one will better another
The 1794 will likely be more resolving and dynamic were as the soekris will be more linear or a little smoother

Sometimes things are just better
I'd say this could be up to preference

This is a top class full audio source with the sd card and the added versatility of the usb input

I think it's great bang for the buck
Granted it's a bit of work but that can be fun too

[randytsuch]

Yeah, sometimes things are just different, and it comes down to preferences.

Being able to connect both the SDP and a USB will definitely be an advantage.
Guess I can't give up my audio PC yet lol

Randy

[Sligolad]

OK started looking at a case layout and after different approaches I ended up working off the same size window as the standalone SD Player unit some of us have.
This will give the option for anyone with the SD Player full unit to use the good case and SD Player front, SD board, rear panel with inputs and AC in and possibly the Traffo from this unit depending how we power the unit.

I have started printing a cage for the big super-caps Nige has to get these in a container first and this cage will keep the caps compact and they will fit in OK as you will see in the pictures. It will save any accidents during prototyping and testing by keeping them together.

The SD Player full unit is too big to print for my 3D printer so I will look to make a 2 piece construction over the length which can be joined to create the full length.

In the pics below I have added in the components in what seems like the best layout so far.
There are two torroidals in the back but we will probably only need one, will wait for Nige to come back on this.
The 5 section regulator board is ahead of these toroidals, the super-caps on the left side, the USB in ahead of this on the lower level with the DAC board above this.
This layout keeps the i2s lines close together in that corner of the DAC and I can get posts up from the base to support the USB board and the DAC board, I think i can also accommodate the original SD board that is in the USB full unit there as well.

Anyway have a look at the pics and any feedback welcome, will probably start printing a case section from tomorrow and try and have something for the coming weekend.

[Sligolad]

Something else worth considering for the build is a clock upgrade.
I had removed with some difficulty the 22.57 clock off a spare SD player board i had and tried adding an expensive Neutron star spare clock unit i had in to the reclocker and SD board but it was not great. http://www.newclassd.com/index.php?page=36

This weekend gone I tried a JL Sounds Oscillator board http://jlsounds.com/oscil.html with the Crystek CCHD 957 clocks http://jlsounds.com/crystek.html which I had spare and got a great uplift in musicality and the sound really opened up.
We can test this at one of the meet ups just to see if my ears still work but I expect the improvement to be easily heard by all.

I added two outs off the clock output on the JL Oscillator board with one going to the MCLK in on the reclocker and the other going to the MCLK out off the SD Player board (no clock on the board) and it worked great, reall surprised how much improvement I got in the overall musicality.

I will try again at some stage with the Neutron star unit as I may not have connected it in this same way above back when I tried it just to be sure.

UPDATE: tried the Neutron Star in the same configuration as the Crysteks and now working perfect, need to do more listening to see if they are worth the price....doubt it really but lets see!!

[nige2000]

what clocks were u using before? ndk's?

[nige2000]

the supercap cage looks perfect,
not sure about bringing the audio out over the traffo ?

id guess the 1 traffo will be smaller than 80 dia 40h ill email toroidy tonight

funny i mentioned it to fran about about a local oscillator boards for better clocks the other day
ive ordered some of these for testing

for that purpose i was gonna use ndks maybe even steal them off the diyinhk usb board

[Sligolad]

Was hoping one traffo would work so we can shove it over to the Supercap side, that is where the AC in is on the SD Player unit as well.
The traffo diameter i modelled was at 83mm so we could even go bigger.

If only one used and still keep the DAC board side of the case free to run the audio out down the same side, again this is where the RCA outs are in the SD Player unit.

I had been running off the standard on-board clock until now, had not hooked up the NDKs that i had soldered onto a reclocker board yet.
I expect any clocks are better than what we have on the standard board.