DS USB input


#1

Hi @tedsmith

I’ve been getting some of the funny behavior with the ISO REGEN detailed here: https://www.computeraudiophile.com/forums/topic/31877-iso-regen-listening-impressions-kicked-off-with-some-measurements/?do=findComment&comment=714912

It happens after hours of music playing, not minutes fortunately. The ISO REGEN (hub) loses connection and music stops. I’m guessing that’s the result of the static buildup and then the discharge.

Of course it may be other parts of my system causing this but the DAC/Pre isolation is mentioned in that post above so just wanted to double check the DS side of things with you.

I swapped out the Corning optical cable to rule that out, for a Supra certified cable both upstream and downstream of the ISO REGEN. But I still get the same result after some hours of music playing.

A generic Cheap-Charlie hub has no issues in this exact same chain, so I assume it’s this isolation chip of the ISO REGEN, as discussed in the post above. Also with the isolation switched OFF there are no issues. Which leads me to believe it’s the ISO part causing issues. I do understand the Regen has many more benefits than just the isolation but I’m trying to understand what interaction of the isolation between the Regen and the DS may be causing this.

The 24/192 Stereo Bit Perfect test passes with all combinations of cables above - the Uptone 90-ohm USPCB, the Corning optical and the Supra certified USB. But I’m sticking with the Supra certified cables on both sides of the Regen for all troubleshooting since that’s the only one with the USB logo on the box. And the Bit Perfect Test passes with both Regen isolation on and off. So I’m trying to work out why the isolation causes the hub to briefly lose connection and stop the music in the process.

So that’s the background info for the issues I’m having. The questions I had were:

  1. Is there any kind of digital isolation of the DS USB input? If not, is there anything that comes to mind as to what may be causing this, at least from the DS USB input side of things.

  2. If I followed Uptone’s recommendation of trying a wire from the ISO Regen output to a chassis grounded point of the DAC, then could I try wire under the screw which is above the Toslink input, as a chassis grounded point? Or is there a better screw to use for earthing?

Appreciate any advice


#2

The USB on the DS is very solidly connected to the case ground. There’s no reason to attempt to ground it better. One thing that I’ve run into is that sometimes the USB cable is the only thing providing a common ground between, say, my laptop and the rest of my system (e.g. not all laptop power supplies are grounded.) In that case isolating the USB ground input is likely to cause a 120V signal between the USB on the laptop and the DS. Depending on how good the isolation is implemented this may work fine or it may lock up when there are spikes on the power line. If you have a multimeter (or scope, etc.) you might see what the potential is between the DS and your source, you might need to try both measuring on a DC scale and on an AC scale, depending on what’s causing a ground differential.


#3
Ted Smith said One thing that I've run into is that sometimes the USB cable is the only thing providing a common ground between, say, my laptop and the rest of my system (e.g. not all laptop power supplies are grounded.) In that case isolating the USB ground input is likely to cause a 120V signal between the USB on the laptop and the DS.
Many thanks Ted. In that linked post Uptone Audio are saying it's an issue downstream of the Iso Regen's isolation chip, not upstream. But indeed my laptop (Microsoft Surface Pro 4) has only a 2-prong plug, so is not grounded. But the single USB output from my laptop goes to a 7-port powered USB3.0 hub, which is powered by a Mean Well 5Vdc grounded PSU. From one of USB those ports on the 7-port powered hub, I have the Supra USB cable going to the Iso Regen.

And if the DS USB input is very well grounded then attaching a grounding wire to the output of the Iso Regen (as per Uptone’s recommended solution) won’t help with anything. Downstream of the DS I have balanced XLR’s into the Oppo HA-1 headphone amp, and then balanced cable direct to my headphones, so that’s all well grounded too. So there shouldn’t be any issue with any built up static being discharged to chassis ground at all, anywhere downstream of the Iso Regen.

I don’t have a multimeter but will try to borrow one. If I borrow one, can you guide me where exactly I need to measure. And what would be the solution if this revealed an issue? To actually ground the USB connector on the input side of the Regen? Even if the 7-port powered USB hub is grounded?

If it’s an issue upstream of the Iso Regen, then I would completely understand this is not PS Audio’s problem at all but any further help/general thoughts would be immensely appreciated.

I wanted to try as much troubleshooting as practicably possible, before I report this to Uptone.

Many thanks again


#4

One thing I meant to say is that if you do experiment with grounding, the TOSLink screw is probably the worst place: it’s screwed into plastic so it’s easy to strip and it doesn’t make a very positive connection to the case (and it’s smaller.) I’d use one of the screws for the bridge/bridge slot cover plate. If you unscrew the wrong thing you may loose a nut inside the case and have to open it up to fix it. The PWT upgrade instructions may help to check for screws / nuts, etc. As I said I don’t have my DS in front of me right now…

To measure between the DS and a source you can just press one probe of the VOM firmly onto virtually any non-black screw or hardware on the back of the DAC. For your source you’ll need to find a similar solid grounding point.

Uptone will really be your best bet for ideas to debug this.


#5
Ted Smith said

Uptone will really be your best bet for ideas to debug this.


Thanks. At least I can tell them I’ve been proactive in checking the DAC side of things (isolation and grounding, as they suggested) so we can at least rule that out.

#6
Ted Smith said I'd use one of the screws for the bridge/bridge slot cover plate.
Crickey. So I followed Uptone's advice and connected a wire from the Regen output to the Bridge cover plate, as you advised.

Up to now music would only play for ~2 hours before cutting off. I haven’t had more than ~2 hours continuous music playing with isolation on.

With this wire added and isolation switched ON, I left it playing overnight and 6 hours later… music was stilling playing. Happy days. And with ground isolation on, it sounds noticeably better too. Not earth shattering but noticeable.

So their theory that this is caused by an interaction downstream of the Silanna isolation chip is correct, at least for my system.

But what interaction do you think is doing this? Since there’s no digital isolation of the DS USB input and the USB input is proper grounded.

It’s not the prettiest solution but for whatever reason wedging the wire between the USB adapter and Regen provides a better static discharge path to ground, than without. I ran the 24/192 Stereo Bit Perfect test just to make sure wedging wire into the Regen output didn’t mess up anything and it passed the test.

When I look at this solution with my eyes it kind of looks like the ‘external wire’ shielding solution John Swenson has discussed on DIY cables which I’ve posted on another thread here, which (I think?) is known as a PEC (Parallel Earth Connection) outside of the audiophile world, maybe? A little like the old fashioned ground wire used parallel to turntable RCA cables, between turntable and phono preamp. I don’t know if it’s the same theory that’s fixed this but just visually it looks like that.


#7

@em2016 I use the ISO Regen -> USPCB -> DS USB input and can play music for more than 2 hours with the switch on ISO at the Regen end.

Do you have the 5V on the USPCB on? I have it switched on and asked Uptone about it. They say it makes no difference if the 5V is not needed - if it is it will just draw the current and if not no. But others have reported it sounds different with the 5V off.


#8
yacheah said @em2016 I use the ISO Regen -> USPCB -> DS USB input and can play music for more than 2 hours with the switch on ISO at the Regen end.
Yep, as per the Uptone post I linked, whether someone has issues or not, is completely system dependent.

And yep 5V was always on with the USPCB, to avoid any potential issues with handshaking. It might sound different/better but I wouldn’t want it for connection issues. I already have enough connection issues with the hub disconnecting.

But I troubleshooted with certified USB cables anyway.

I’m sad to report I was premature in declaring this problem over. The issue came back. I even used an earthing plug on the Regen output. So it’s definitely not a grounding issue downstream of the Regen. It must be as Ted hinted, upstream, but even that is grounded with the Mean Well 5Vdc grounded and powered 7 port USB hub. Everything is on a single power strip (only wires between all outlets, no filtering/conditioning etc). There’s no issues with the isolation switched OFF, so lifting the ground on the Regen is doing something funny. I need to contact Uptone for help trying to solve this.


#9

@em2016 I just saw your post on CA’s ISO Regen forum and wanted to chime in here too.

I have the same issue as you do with the ISO Regen now powered by the LPS 1. I had the impression it didn’t occur as much powered by the iFi 9V iPower and very rarely using the W4S Recovery in place of the ISO Regen.

I started another thread to warn DS users intending to buy the ISO Regen for the galvanic isolation aspect since it is problematic working with the DS.

If other ISO Regen users with DS DAC’s have similar or different experiences please chime in here or at my other post.


#10

Hi,

Are you getting the USB connection to the DS USB disconnect every 2-3 hours like I was, or more frequently?

I’ve since sold my DS and moved to a Chord Hugo2 for portable use and soon a Chord Dave for the desktop.

Btw I didn’t sell my DS for this issue or any issue and my listening experiences with the DS were ALWAYS incredible.

But I found the Dave (and even the Hugo2 on a smaller scale) to be something else, especially as single box (DAC+Amp) headphone solutions.


#11

No issues with mine, very stable from day one.