A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

Last time I checked this thread is contained within the DIY Audio forums
If it would be preferred should we start a new thread concerned with modifications?
Now now, aren't we being a little touchy now? :D;) I think this thread should continue just because it contains such an enormous amount of information for those that like DIY.
wCH5BAEAAA8ALAAAAAAPAA8AAARC8Mn5gKVYgmNAxoBReB8FFARZVsX4WZYhpmAXcuigsoQu5ztYrNULznSookkIIBSNQMBgENhVhNNAFQTUbjPMyyQCADs=

Look, I'm new to DIY-audio. It's only a few months I made my own simple tube amp. But I'm not the brightest guy in DIYaudio. So when I discover the DDDAC I want to know for sure that I'll get enough bang for the bucks. Finding an elaborate thread like this one, could create the impression that the DDDAC is quite OK but not as good as it should have been. Thanks to your reaction and the others I'm now convinced this really is a very fine product that'll play very well even in its default configuration. :up: And let us all have a bit of this now : :cheers:
 
I think Rick mentioned a new mod thread because it happens in other designs that a design/support thread is kept separate from a modifiy thread, to help extermely busy people like Doede. The design/support thread is left for troubleshooting the stock product and the modify thread for leaving the "default" build path! Happens often for design/discussion versus the actual "group buy" threads. It does keep the signal to noise ratio down on all threads...
 
And to think I thought there were others getting touchy.

No, what I took from those posts is the typical plug and play attitude that resists exploration because of lack of inclination or time and somehow want the world to stop or at least progress at their pace.

I agree with palmito (as I usually do) that in fairness to Doede and to newcomers that this thread should be reserved for folks building things for the first or second time and need his assistance.

Doede has not participated in the modification posts very often, anyway, which shows he has a benign attitude to this; he certainly has been tolerant of these posts which is appreciated. It will be interesting to see which, if any, of the suggested mods make it into the next board.

It would make the whole thing more succinct for those wanting to try some mods without having to wade through the same questions over and over again which is what usually happens with threads about a product. See the BOTTLEHEAD forums for the perfection of this idea. Every day the same questions ... (lost interest years ago)

Since SUPERSURFER was the intrepid one starting the modification discussion would he mind starting the thread? It would be good if we could compile the basic posts and hope more comes about as we learn more.
 

Hi James,

Now I finished the boards I noticed that placement of the 8v shunt is possible on this spot.
If you use the bridge wires for the outpud leads in the dac boards rev.3 there is room to place the shunt above the holes for A pos and A neg.
If you own an older board it will also be quite easy to jumper these on the dac boards in order to lose two output wires.

First comments on the running in:
-there is significantly more openness, detail and decay of tones.
-the sound is more layered and airy, the silmics bring a nicer balance than the somewhat dark sounding muse. I think using an array of the same value caps will strengthen the sound color of that type of cap, thats why I use different values in capacitance and voltage. This brings more openness and detail in the so important mid regions.
-I changed the wimas around the dac chip to 0,068uf. This makes the highs more coherent; it shifts the responce of these caps to a higher frequency region fitting the silmics better. The result is that for instance voices are more real and less pronounced in the "SS" area.

I think the way the dac is developing now brings it to an exceptionally high level. Commercial dacs will have a hard time beating this.

I would guess all these mods will make Doede happy :p. It brings a bunch of ideas for him to develop his new revision dac boards. And as been said here before, we wouldn't bother with modding this board if it wasn't such a nice design to start with.;)

Regards,
 
Disabled Account
Joined 2002
would be nice

Hello,
I remember a forthnight ago i did start reading this thread and i was wondering do i have to read all this. Using google you will always be '' dropped in '' somewhere in the middle. You should begin at page in and store some of the post in your memory.
Having one thread for the '' normal folks'' and another one for the diy crowd could be nice.
Maybe i will wait until there is a new board with some further improvements. Still have some other projects to finish.
Sincere greetings, Edward
 
Hi James,

Now I finished the boards I noticed that placement of the 8v shunt is possible on this spot.
If you use the bridge wires for the outpud leads in the dac boards rev.3 there is room to place the shunt above the holes for A pos and A neg.
If you own an older board it will also be quite easy to jumper these on the dac boards in order to lose two output wires.

First comments on the running in:
-there is significantly more openness, detail and decay of tones.
-the sound is more layered and airy, the silmics bring a nicer balance than the somewhat dark sounding muse. I think using an array of the same value caps will strengthen the sound color of that type of cap, thats why I use different values in capacitance and voltage. This brings more openness and detail in the so important mid regions.
-I changed the wimas around the dac chip to 0,068uf. This makes the highs more coherent; it shifts the responce of these caps to a higher frequency region fitting the silmics better. The result is that for instance voices are more real and less pronounced in the "SS" area.

I think the way the dac is developing now brings it to an exceptionally high level. Commercial dacs will have a hard time beating this.

I would guess all these mods will make Doede happy :p. It brings a bunch of ideas for him to develop his new revision dac boards. And as been said here before, we wouldn't bother with modding this board if it wasn't such a nice design to start with.;)

Regards,
An excellent, well thought out tip, but most of all, perfect timing [emoji2]
I hadn't realised those wires are joined anyway on the main board, so if we Bridge them on the DAC board (I have the old one, so used wire links under the board) we only really require 2 wires out per channel, not 4..

I moved my shunts this evening to be as close as possible to the DAC chip, in the Wima decoupling cap positions as discussed and with small wire bridges to the vcc for L&R analog. I'll explain a little more when I find some time, but here's a quick couple of pictures to explain
6e4azuma.jpg


An externally hosted image should be here but it was not working when we last tested it.


ma2avyma.jpg


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


y8uvaduh.jpg


Stupidly I didn't get any pics of the underside of the board to show where I cut a couple of tracks and added the wire links, but it's nothing special.

I didn't change any electrolytic caps for now.

Initial listening impressions show an improvement in clarity and airyness. It was a pretty fiddly job, but I'm glad I did it now [emoji3]
 
Last edited:
Whilst I don't have one of these as yet, would it be possible to place specific power supply caps under the board to allow closer and simpler install of the tent regs next to the chip. If able to get close enough the caps could interlock possibly and may not require any further spacers between decks, allows the shunts above for cooling as well.
Just a thought,

Chuz,

Drew.
 
My view on the mods and threads is very straight forward :)

Please keep posting mods and experiences. I always wanted my designs to be two things

1. very good whilst affordable, out of the box, better than most other products at a affordable budget

2. offer a starting point or platform, for the hard core DIY, who have lots of fun on trying al possible things to improve their sound experience, without looking at budget and hardware limitations :cool:

I believe I had a good shot at both objectives with the dddac1794 series, so we can continue the thread as is.

of course I hope the red band of point one wil not go under for new readers, so we may be need to remind the world out there on that point so now and than :p
 
another point on my contributions, or rather lack of ...., to the modding story. well very simply, that has been caused by extreme lack of time.... But it is not gone of course, I do like my hobby as you do and indeed at the background I actually do stuff, but it has been slow. too slow :rolleyes:

I hope to surprise the thread readers "soon" with some feedback from my side :D

stay tuned !
well, you do any way, right? :p
 
My view on the mods and threads is very straight forward :)

Please keep posting mods and experiences. I always wanted my designs to be two things

1. very good whilst affordable, out of the box, better than most other products at a affordable budget

2. offer a starting point or platform, for the hard core DIY, who have lots of fun on trying al possible things to improve their sound experience, without looking at budget and hardware limitations :cool:

I believe I had a good shot at both objectives with the dddac1794 series, so we can continue the thread as is.

of course I hope the red band of point one wil not go under for new readers, so we may be need to remind the world out there on that point so now and than :p
Thanks Doede,
If those were your 2 objectives then I would say they have been delivered perfectly :)
In its standard form, the kit is easily accessible and well thought out and delivers a sound quality for the money that is very hard to beat.
As a platform for further modifications, it's also wonderful and your hard work and testing with the 1794 NOS implementation really shows.
You say these are big budget modifications, but I strongly believe that for less than £500 including the streamer, I now have something which beats most commercial systems costing 10-20 times as much and that's just incredible! :)

If there's anything we can do to help with your time and testing, please just say. I know it's time consuming to recreate modifications like we have done, but that's the only true way to measure and quantify the difference they make. If you wished to borrow mine for a week or so at some point to compare, please just ask :) I'm not pretending this is the ultimate version, but it may give some helpful feedback for your design.

Looking forward to seeing what is coming up next :)

James
 
Hi Supersurfer. While studying this picture you posted I noticed you'd used the "Alternative option (do not connet "A")" jumpers. Did you think it made an improvement?
I'd be very surprised if there's any difference. It's just a question of whether you run the 4 output wires down into the mainboard and join them into 2 there or join them at the DAC board and just run 2 down to the mainboard. There's no components involved in the change and technically the circuit does the same thing both ways.
I did the change on mine and removed 2 wires per channel from DAC deck to mainboard, but that was just to get more room to mount my shunt regulators.
 
Looking forward to hearing from Doede more often.

When asking a few questions early on he could be anywhere in the world when he answered. How he found the time to run the webshop, design audio devices AND make a living made me tired just thinking about it. Now that he has shaken free of the webshop and can devote more time to the two most important aspects of life this thread should get very interesting.

I came across something interesting on the BELLESON site. Since I seem to not be able to elicit a response from Mr. Tent and have not mastered the skill of begging for an answer and actually getting one I figure I will build a board with the BELLESONs I have.

The interesting thing is Brian's suggestion of using a "pull down resistor" between the output and ground pins of his serial regulator. To quote from his site:
An unipolar regulator is great for sourcing current but not good at sinking it, and the pull down resistor compensates for that. For example, when load current changes from large to small, a transient charge appears at the regulator output and the pull down allows that transient to dissipate quickly rather than slowly. This greatly improves transient response.

He recommends throwing away about 20 mA with the resistor

I think this might make the difference between shunt and series much smaller than without this resistor. Very simple and sensible. Could this minimize the difference between the two approaches?

Forgive my laziness - I am sure it is in here somewhere - what is the current requirement of the 3.3 and the 18 volts supplies per PCB?

Thanks,
 
Last edited:
The interesting thing is Brian's suggestion of using a "pull down resistor" between the output and ground pins of his serial regulator. To quote from his site:
An unipolar regulator is great for sourcing current but not good at sinking it, and the pull down resistor compensates for that. For example, when load current changes from large to small, a transient charge appears at the regulator output and the pull down allows that transient to dissipate quickly rather than slowly. This greatly improves transient response.

He recommends throwing away about 20 mA with the resistor

I think this might make the difference between shunt and series much smaller than without this resistor. Very simple and sensible. Could this minimize the difference between the two approaches?
,


This is not more than a bleeder resistor. This resistor will be able to sink some current but not nearly as fast and efficient as a real shunt regulator.

The shunt will change it's impedance constantly depending on the current that needs to be sourced or sinked. The bleeder resistor will stay fixed......
 
Last edited: