I’ll lend you my Audio Research REF160M Monoblocks.
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Just a thought - the channel of the amp that makes the noise may be close to ultrasonic oscillation for some other fault-reason.
If the output of the DS2 has a different ultrasonic noise profile when it is decoding DSD (so it must be early in its processing since it converts it all to DSD early on) than when decoding PCM, that could be tipping the RH channel of the amp into oscillation.
Bit of a reach but does explain why 1) DSD tracks only, and 2) -appears to be happening in the amp.
Doubt very much guys it is any downstream amp - same problem happened in my system. MK2>ARC preamp>ARC power amp. Going from DSD track to a PCM, loud pop followed by whitish hissing noise coming out of the right channel. 1st time it happened the noise faded after 15 secs or so. The 2nd time it was persistent, I had to power off and reboot the MK2 to get rid of it. Before turning off the MK2 I powered off my Holo Red - did not end the noise, so pretty sure the Red feeding I2S input to my MK2, or my Roon Rock ahead of the Red are not culprits.
Running 2.5.1/208. Never had a problem before I did the upgrade.
Haven’t tried playing anything digital since…sticking to vinyl while I wait for Ted to figure it out…
By any chance was the PCM track 24/44.1?
Sorry, did not catch that detail…
Joma, I had similar thoughts about the amp perhaps having an issue with ultrasonics in its right channel, if I am understanding correctly that connecting the DAC’s right output into the amp’s left input still produces noise from the right speaker. But trying to map that onto playing DSD vs PCM is really challenging.
The FPGA doesn’t convert PCM to DSD per se until the very last stage. Moreover, DSD input is handled only a little differently from PCM: native DSD is packed into DoP packets, and DoP contents are mapped into the upsampling space one full-scale bit at a time (at 16x the “sample rate” of the DoP) instead of PCM sample by sample. This data is then upsampled, a lot. That this can be done, with the exact same upsampling algorithm applied to these seemingly incompatible audio encoding formats, is the key to understanding the DS DAC.
Anyway it means that the entire spectral content of the input data is present in the upsampled signal, including the inherent ultrasonic noise from DSD. Perhaps if the input is DSD64 some of its noise floor (the rising line seen on FFT plots of DSD) is faithfully transferred through the remodulation to DSD256 for the DAC’s output stage. @tedsmith is this a reasonable notion or have I something more to learn?
So @JohannSeb it would be interesting to have your amp connected to some other true DSD player and see whether the right channel is just overly sensitive to ultrasonic noise. Another Directstream DAC (any model) would be ideal, but there might be some SACD players or other makes of DAC which could do the job also.
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Both 198 and 208 of the FPGA code have a 6th order filter with a 3dB point of 110kHz so frequencies above that even in DSD will be attenuated. (FWIW 179 didn’t have this particular filter and a little more DSD noise would get thru as you hypothesized.)
When the DS Mk I came out I had a lower cutoff for the filters because I was worried about the number of preamps and amps out there that might be sensitive to the ultrasonic noise. It is the case that the DS MK I and Mk II let a little more ultrasonic noise thru than most SACD players. Universally people preferred the sound of more ultrasonic noise than that of filtering more of the highs out. With the DS Mk I I only remember one customer that had to use a preamp because his amps didn’t like the ultrasonic noise. (PS Audio support may know of more, but the number isn’t very high.)
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Good to know about that low-pass for the new DAC, thanks.
But it still seems like there could be a corner case where the bottom part of the DSD64 rising noise floor could sneak out underneath a 110kHz filter and perhaps be enough to unsettle a failing amp circuit. And because even high-res PCM tends to have near-zero energy above 40kHz (and therefore less to filter out) that same amp might be fine with PCM played back on the same DS DAC.
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I have a similar experience as @lanetim.
When running 2.5.0/antero 208 switching between tracks with different DSD resolutions produces a loud pop every single time. I also experience the white/static noise from the right channel a few occasions.
Downgraded back to antero-198 and that eliminated all pop and white noise issues for me.
The main difference with what others are experiencing regarding the loud pops is that they do not happen when switching PCM to DSD or viceversa, they only happen when switching from different DSD resolution tracks.
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For my part, I will wait until all the errors mentioned are corrected 
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Smart move, Jose. Things are being worked on.
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@jkrichards Wow you guys certainly do try to help. You’ll deliver of course. Silver or black though? I’m very fussy about looks you see…
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I too have had an issue with intermittent loud hissing (both channels this time). It only happens occasionally, but requires a reboot of the DAC for a couple of minutes. This only ever occurs on DSD (both on SACD playback vis PST and streaming via 12S, and can happen mid-track). Again, if I switch to PCM the hissing is gone, but there again if I switch back to DSD. I didn’t mention it before as it’s so intermittent but scary when it happens as it’s very loud and potentially damaging to the speakers. I’m now wondering if it may be a related issue and help with diagnosis?
@dvorak I have indeed connected up to a MK1 DAC for comparison, and am finding precisely the same issues only on DSD (rare intermittent very loud hissing on both channels solved by a reboot of the DAC, and background noise on the RH channel which is always present).
Johann, so you’re saying you are getting the same behavior with the DSD MkII and MkI?
Correct.
Wow now that makes me think something else
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Yes indeed.
I think we must be looking at my Jeff Rowland power amp being overly sensitive to ultrasonics, albeit just on one channel (hence why the issue persists across the MkI and MkII.) I just hope it isn’t a precursor to some sort of catastrophic failure. I will content myself with non-DSD listening, or in the case of files converting to PCM, which sounds more than acceptable on the Mk II 
Thanks to all who have helped narrow this one down for me, much appreciated.
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I got a USB drive from PS Audio (many thanks) and I’m going to wait a week or two more before attempting to load it as the Mk2 and the M-1 fuse are just now “broken in” and I want to listen to it more in this stage before making further changes.
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After swearing off the 2.5.1 GUI and avoiding music streaming over a week due to nasty shrill harshness and flabby bass , I was getting out of the MK2 again. i decided to do the factory reset and reinstall the HDMI shorting plugs since 2.5.1 the bug that kills the i2S power off
Glad to report all is well sound wise again. Any word on new GUI firmware release?
Were you ever able to track down this weird one?
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