I didn’t write to offend you, I’m sorry if I caused you upset. I wrote it to highlight radical modding. I wouldn’t be here if I was against modding. But for DS, my preference is for mods approved by @tedsmith.
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Do not be offended, let’s accept that we do it primarily for our own satisfaction.
My goal was also to propose solutions that I have tested, some of which are very easy to apply and can achieve a significant improvement in sound quality at a low cost. Until recently, I treated the manufacturer’s PCB as a sanctity that cannot be violated. After my experience with capacitors, I know that any equipment can be improved.
Even if the improvements are imagined.
Modding is like a box of chocolates - you never know what you’re REALLY going to get until it’s done, but it’s always fun.
Luckily, this forum has the advantage of having advice/input from @tedsmith, the designer himself to give advice and guidance on what is likely to work, what is likely not to work, and what is likely a total waste of time (which saves both time and money).
He would be tantamount to the PS version of Nelson Pass, who freely gives advice on modding his equipment.
I know a proverb: Not saints make pots.
Each item is man-made, and we should not be afraid that something is beyond our capabilities. Especially since we have read many times that many compromise solutions were used when designing the DSD.
@Turbotk please reconsider your decision to delete your posts. Many are interested in what you are doing.
If you you are willing to restore your posts, let me know if you would like my help in doing so.
Rock and Roll!! I imagine that all the new components down to the purple fuses must burn in with play. So far so good straight out of the box. Even my tuner sounds better even with the dac powered off. Perhaps coincidence?
Things will get hairy at timesand raged with purple fuse burning in. But yes better out of box initially and way better over 200 hours.
After the Directstream dac mods with Keces P3 power supply and with my Audioquest Dragon HDMI cable and my Wel Signature AES/EBU cable I am getting the best sound I have experienced in my system. The sound is incredible and the parts will burn in over a couple of hundred hours.
Well I finally was able to implement one ~ “final” (?) electrical mod to my DS, and it might actually be the biggest of all in fact based on what I’m hearing. May be we saved the best for last. So felt I must share here.
So meanwhile by now we’ve done the more obvious things. In my case a progression from stock output transformer (OPT) → XS4400 OPT → no OPT w/ some super high quality caps → mu metal OPT → amorphous OPT. And soon now we will have a pair of amorphous w/ pure Cu windings. I think it has earned it 
Suspect that, especially considering the footage involved we’ll benefit audibly from the “quietest” conductor we can get in there. Though if I had the choice it might not be the Cardas. But it’s all we can do for now.
And by now we’ve also substantially beefed up (in the high end analog circuit sense) each of the (8) local op amp PSU’s along with the several upstream nodes that feed them. We’ve also beefed up the DSD bit slinger PSU as well; personally I consider that part of the analog in this DSD case .
But to the mod here- It’s been in the back of my mind for awhile: what exactly should we do about the Vocm node in the op amp circuits. Thinking out loud here, that node defines the exact center reference point of the differential output waveform. Thus it’s analogous to the VSS node in single ended circuits. Seems to me it must be absolutely rock steady, certainly through the audio band at least. Any wiggle there is unwanted noise then and passes straight through to the output 1:1 with no attenuation. I think we need that dead quiet.
The AD8132 datasheet has a small amount of info on Vocm, and seems there are a few statements that support the above thinking (my emphasis):
In cases where more accurate control of the output common-mode
level is required, it is a best practice that an external source or
resistor divider (with RSOURCE < 10 kΩ) be used. The output
common-mode offset values in the Specifications section assume
the VOCM input is driven by a low impedance voltage source.
BTW the DS design follows the datasheet basically and has a precision resistor 50% voltage divider that creates the Vocm node with some ceramic bypassing in (what I assume is) the ~ high speed sense. A resistor voltage divider generally creates a ~ high impedance output node; only buffering or bypassing brings it down to low impedance. The datasheet seems to imply AD used a buffered, low impedance source to drive Vocm for their best specs…
As an editorial aside here, my opinion, I do not like ceramic caps anywhere near precision analog audio circuits 
Generally speaking they have audible issues- voltage coefficient and piezo effect, basically. In this case I probably would agree though, likely not a big factor (except maybe the Vocm node (?)). But I’m not going to bother trying to rip them out here
Anyway, key point- I think that Vocm node likely needs to be as immovable (ie low impedance) as possible through the audio band; so it really needs an analog class bypass.
So yesterday I added what I think it needed, and the results seem amazing to me so far. Not knowing what to expect at first, after a few Tidal songs the big word that literally leaps into my mind is… TEXTURE… Wow… so much texture and preservation of low level detail. There has not been this level of texture in my system before. It seemed almost overwhelming at first; my brain had to adjust. The sound is correct, natural. That’s what I’m after lately. And as we push forward there can be no going back
The Concept 500 also help in this as they specialize in transparency, correctness and delivering, revealing what they are fed as well.
To make sure I’m not just imagining things, I’m really hoping another person might also try this and report back.
Below is an image showing the Vocm dividers. Please note the Vocm node is not between the resistors as you might assume.
What I did was, I already have a PPS SMD bypass directly across each resistor R_A and R_B. But the real mod is the analog bypass- I placed a Bi-Polar (BP) 47uF Muse across R_B. This bypasses the Vocm node to local VSS. I had these on hand with 5mm lead space which makes them ~ suitable here. And Yes, BP is better sounding than polarized in general. If I had same in 100uF I would have used that instead of 47uF.
The best sounding electrolytic I know of is Kaisai. And I have extensive experience using those. But I think we can get close to that (enough for now) with the BP Muse at much more reasonable cost.
And since this cap affects the signal directly (basically), use only the best. Don’t bother with anything less. If you skimp out and use anything less, we cannot really compare.
And if you have the patience, likely even better would be a 47uF cap across each R, A and B.
Place the “negative” cap lead on the lowest impedance side of the resistor. In the case of R_B that would be the VSS node on the LHS of it in the image.
Looking forward to hearing what others may experience.
Thanks, T
I’ve added some links to quick cell phone clips. Don’t expect the world but maybe some can get a sense of what we’re hearing here. I’m not used to using Google drive but maybe this will work:
Indeed VCOM is a great place to improve things. I don’t like the resistors we used there, but when we were initially releasing the product they (by far) sounded the best. I really believe that even just substituting some thin film, 0.1%, 25 ppm/degree C resistors should make things sound better there now that there have been so many software changes. The Mk II uses an opamp buffer to set that level and the new video opamps have a much higher input impedance on that node.
[Edit: oops, forgot to mention the value. Don’t go lower than about 500 to 1K there.]
Did he ever mention why he didn’t build in the mods from start? I sometimes wonder why mods costing just a few $ haven’t been part of the design (except if parts were not available in a certain quality by then).
From what I have read here and there, he readily admits he can’t think of EVERYTHING, and that’s why he loves the modding/maker community. He feels that everyone improves when everyone shares their knowledge. Once any of his products is out of production, he freely shares the schematics along with his reasonings behind the design. Even before something is out of production, he freely shares the ideas/theories behind his designs (without giving away the schematics).
He’s always engaged with the DIY community in how to make and mod his equipment and regularly contributes to the forums in diyaudio.com.
Like @Paul and @tedsmith have cited themselves, he also states that all products contain a range of compromises from parts to manufacturing. Sometimes it’s a matter of practical cost, sometimes it’s a matter of tradeoffs that have to be made in design. There’s always compromise somewhere - you can’t build a 1000 watt pure class-A amplifier and have it run off 120 volt mains and fit in a house without burning it down (I know it’s a little extreme).
Sounds like a challenge for someone
Yes, I’m aware, the real art is designing with the right compromises to a price point.
When I see how folks tune their devices with add. PSU‘s and parts for hundreds or thousands of $, I just sometimes doubt, whether many such products are not designed past the customer.
I think one problem is, that manufacturers who use even better parts and make less compromises, unfortunately also apply much more expensive design, which often makes products unaffordable. A manufacturer offering very low compromise electronic design in affordable casework would be interesting.
I see PSA in that direction more or less, but not as much as it could be I’d say.
I think Manley is a good example of this concept.
Was that a question for me? What further details do you seek?
T
Yes, for example app photos.
When there was a lack of technical knowledge and a lack of translation, what was meant to be explained was not clear for me.