Asymmetric Room

@audphile1 Great question. Been thinking about that myself. I think the answer is it has always been there. Like all of us, I have been making continuous improvements and the occasional hash is more noticeable or all that is left. I ran the frequency sweep, proving the perceived issue for the first time a few days ago.  
One recent change is I had a smart switch on my Qutest to allow for remote power off that I removed. I suspected the smart switch was introducing post conditioner power supply noise.
However, I found when the Qutest is left powered on, it begins to introduce hash. I manually powered off my Sbooster and both perceived & measurable sound improved, not perfect, but better. 
I will either have to manually power off my Sbooster or bite the bullet and purchase a different DAC. I think I know what your vote would be. 😏

I, like you, was chatting with ChatGPT and Gemini about EMI/RFI and the use of mix-31 ferrite chokes. I ended up buying a bunch of sizes and clipped them onto every power cord and wall-wart barnacle in my rack, plus on the power cables to my subs. The difference was noticeable—my audio through Roon, Qobuz, and even Apple TV streaming sounded cleaner, less noisy. Subtle, but playback felt more relaxed.

I figure each device benefits from having a choke right at the input. You can also stack filters, even at the wall. I added some to my power conditioner too. There’s really no downside—chokes are inexpensive, and the improvements, while not night-and-day, are definitely worth it.

@signaforce agreed on the Qutest!!! I noticed the samevthing - left on it sounds worse after some time and requires a reboot. I would say if possible look into upgrading your dac. There are a lot of good choices there not expensive. 
 

@adsell Great recommendation. I do have ferrite rings (wall wart cables wrapped) and chokes on all my wall warts. Never thought to add to my upgraded power cords. That would be one big choke. Any idea what size?

@audphile1 Interesting you had a similar observation with the Qutest. I would buy a new DAC if I knew that would resolve my issue. chatGPT recommends one of the Holo KTE DAC's, (Spring or May)  believing their sound would be more compatible with my R11's. 3 things.

1. I like the dynamic crisp sound of Chord

2. The size of the Qutest is perfect, although I could potentially install a larger DAC where my headphones currently sit.

3. I wish I could find a try and buy / diagnostic DAC solution. My Schiit MM2 installed on my secondary system recently failed, so unfortunately I can't swap it out for diagnostic purposes.

I have a free day today, so will be playing with different possibilities. Thanks! 

May be try a tube DAC? LTA Aero could be good if you don’t need DSD. They may still have home audition with return policy. Or PS Audio DSD MkII which will be coming down in price (expect good deals on TMR with return policy).