Thanks i trust your dedication and expertise. I have tried walking away. Turning off amps coming back. I waited 7 to 10 days no DAC with little snippets of songs in between no change. Execution the factory reset MK2 finally cured it. Logged it as the firmware burn in. I listened to my system with other sources. No issues during that time or any other time. My MK2 was a Beta. They stopped shipping in November got it like 3 weeks kater December 1. Anyway way of PMing a rework schematic. I can pop the cover and see if I got one that was not completed to the intended design rework perhaps?
For those of you with a Mk 2 and a regenerator, e.g. a P5, P10, P12, p15, P20, does running clean for a few minutes (minutes not seconds) does that affect things? Obviously this is quite different to a reset but I do regular P10 cleans with my Mk1s and BHK250s.
Three approaches: I had a rare bug in the Mk I that required a reset now and then. I’ll keep my eyes and ears open for a similar bug in the Mk II.
If you have the grounds lifted, you may unlift them as an experiment. If the problem goes away or greatly lessens then there’s something like a buildup of static or simply a growing DC offset which might cause a problem. If this is the case there are some little spring tabs that are supposed to give a high impedance connection to the case for each input. If one (or more) of them are not touching the case that might enable that slow buildup of static or ground offset.
If neither or these affects your issue we may be able to get an RMA and send your DAC here so I can look at it and see if there’s something wrong, either systematically or just on your unit.
I don’t run lifted grounds. I tried that and everything was sounding poorly sort of like when it drifts after a system reset. So all inputs and outputs are grounded. I am running a i2s shorting plug on i2s1 only because of the disable bug with 3.5.1.
I go galvanically isolate the USB. I can try without that tomorrow. I was planning to try that anyway with my new USB cord. I just changed USB to a pure silver sir dielectric cable but problem was present prior with the other refererenz cable from inakustik.
I gather if I take off the lid i can see the spring tabs on the inside back pan. Do i have to be concerned with any other than USB and output XLRs? Or does power cord and fuse use them too? Can the unused inputs and outputs cause similar static build up if tabs are not functional though unused?
Every digital input and audio output has a small finger or bent loop with a 1MegOhm resistor to the local ground and which should make a good connection to the case. There were some units which somehow got over sprung or broken off in shipment. At least one unit had a rattle which was the little finger lying on the bottom of the case.
Any input or output that has a cable attached, whether that input or output is being used, may potentially cause a groundloop issue (or a lack of a ground issue.)
The power cord and fuse aren’t a problem: The power cord has the safety ground instead. The fuse doesn’t have a metal case.
Pardon my ignorance. What exactly is the definition of the term lifted? I’ve been under the impression that lifted means that galvanic isolation was turned on.
I will try restoring ground to USB. I doubt it is USB since I had similar issues with i2s in early beta. Everyone else was extolling virtue and I struggled with firmware updates.
If it keeps going noisy I will perform a shake rattle then lift the cover. Looking for ground issues. I have been fighting this one from the beginning I believe, but the times that it performs it really performs and sounds flawless. I was writing it off as poor sounding recordings , but other times it plays anything you throw at remarkably. It sure doesn’t sound like a analog ground loop. My speakers have no hum with ear to them. The DAC is silent too.
It sounds like one has to take more care than MKI disassembling the digital card from the back panel if upgrading transformers to pull analog card. I don’t recall seeing little loops or 1 meg resistors in my MK1.
I grabbed a few hours. Ted has been helpful and insightful for new places to look. Hopefully I can avoid shipping it off to his place. I will have to try the DAC in the Babyface FS or feed a SPDIF from the matrix to my processor. I can always use the Apple TV as a Roon Endpoint to my processor and skip the Bacch4Mac or dust off an old emotiva Stealth dac too if this problem beats me. Nothing like a USB cord 9 times more expensive than a DAC.
It is hard to pinpoint the cause and I am no help since I have not had any similar issue to yours. PST was running great; Streaming DSD files was fine. As I mentioned earlier, I need to reboot the streamer to make SQ alive on Qobuz occasionally.
Yes it does. But even so, using a one megaohm resistor to ground is still correct behavior. You don’t want two completely isolated devices (e.g. if a laptop were the source and running off of batteries) having their grounds drift apart by thousands of volts. There’s a limit to the voltage that can be isolated (even with pure optical isolation.) Putting a very weak resistor between them keeps the grounds closer together but doesn’t transmit any measurable amount of current.
[Edit: when the ground isn’t isolated the connection is approx 0.04 Ohms, when isolated the one megaohm resistor will conduct -147dB of that current.]
I’ve actually rolled back to179 because of stability with 208. I run all settings default and have also noticed the sound fading or changing after the MK2 runs for a while, but I can hear the change after 30-60min. 208 for me is also real finicky with the install and reminds me of my DSJ in that regard. This may be a result of 2.5.0 and 2.5.1, but when installing 208 the FPGA verification step is usually skipped. When I get a clean install I definitely know it, but it can sometimes take a while to achieve, and even then the sound quality doesn’t last. With 179 and 2.3.3 everything installs clean and the sound remains stable.
Yes… I found that the grounding finger on both i2s inputs was pushed back and not making contact to the rear of the chassis. They are too close to the plastic surround ring around both i2s connectors. I had to bend them slightly away from them surrounds and bend them back out toward the chassis.
It seems that the rough anodized surface might might hinder a good bond but since there is a 1 megaohm resistor that might not be that important. I do wonder what milliohm resitance might measure? I guess I am just used to aerospace where less than 5 milliohm must be demonstrated on each joint at install with meters.
Thanks for showing pictures! Your attention to build details is first rate!
Note the small circle where the contact connects to the chassis. This is mask to keep paint out of that area. The metal that the tab hits is not anodized.
