Fiber Optic isolation causing listening fatigue

@surlydale your ears have spoken. No further experiments necessary. Enjoy the simplicity of your setup without clutter. 

@surlydale 

"emphasizing the higher frequencies of the cymbals. When Miles began playing many of the trumpet notes were just too hot."

I said the same thing when I reduced noise in my system with a Shunyata power cables and a conditioner and when adding the N150 that you have.  I thought I was hearing things.  Both added more details, but I felt like it increased the energy in the upper frequencies.  I don’t fully know why but based on my best research, 1) the noise masks the high frequency details, allowing you to here them hence you perceive them now, and 2) the greater amount of details in the signal from a more resolving system allows you hear the high frequency details (which were simply missing before due to a lack of resolution).   I am not commenting on any benefit to fiber - I am a doubting Thomas type of person for audio and a switch to fiber falls in the category for me, but this hobby often surprises me so I don’t question upgrades and I know people have better ’ears’ than me.  My solution was two part - I was not going back to a system with noise masking the extra details so I swapped in a pre-amp with NOS tubes and swapped out my DAC (which was said to be hot on top) for an R2R. 

The following is from AI (Super Grok)  so take it with a grain or two of salt, but it does make sense to me.  

• Noise in an audio system—whether from electrical interference (e.g., AC hum, EMI/RFI), component self-noise, or jitter in digital signals—acts as a "floor" that can mask subtle details in the music. High frequencies (treble) are particularly vulnerable to this because human hearing is less sensitive to them at lower volumes (per the Fletcher-Munson equal-loudness contours), and they tend to be lower in amplitude in many recordings.
• When you lower the noise floor (e.g., through better power conditioning, isolation, or ultra-low-noise components), these masked high-frequency elements—such as harmonic overtones, reverb tails, or transient attacks—become more audible. This doesn’t add new high-frequency content; it simply unmasks what’s already there in the source material. The result is a perceptual increase in treble energy, as the music "pops" more vividly against a quieter ("blacker") background.
• In psychoacoustic terms, this is similar to how removing broadband noise reduces auditory masking, allowing finer details to emerge, which listeners often interpret as enhanced brightness or extension in the highs.

@foggyus91 Thank you for that step by step.  I understand now....haha. Do you think having a battery operated streamer would give you more of the same benefits?  

The downside of this approach is the noise these devices can introduce into an otherwise clean AC.  That's why I stick to passive galvanic Ethernet isolators in my system.  On the entrance to my house I use fiber to block surges, but that's all. 

Sadly you are mistaken, what noise is being passed? What is the source? the 902 is a client (only my Zenith is on the client) and is off the grid using Anker 28k in series. I had fiber (HQ Fiber also not the Amazon crap)now it is gone, 2 less boxes and 2 less LPS to make noise. Guess you will never know a truly black background in streaming. 

@brbrock maybe??