XVive U5

SNR is confusing topic and always needs to be put in context. Start with these assumptions:

In the real world, you can easily damage your hearing at listening levels of 100 dB SPL, so you don't want to do that.

In the real world, you'll have a hard time finding a room that is not custom-built that has an ambient noise level lower than about 20 dB SPL.

Given 1 and 2, that's an 80 dB signal-to-noise ratio, about the maximum that is actually useful. This is also about the best signal-to-noise ratio that can be achieved with analog recordings. In most analog recordings it was less than 60 dB.

Almost any digital recording system (even your phone) is capable of much better signal-to-noise performance than previous analog recording systems.

Typical high quality condenser mics have a noise output about equal to your very quiet room--somewhere like real sound of 10 to 20 dB SPL.

Given those assumptions, if you're going to actually hear noise in a recording system it will be because you are amplifying the sound--making it louder in its reproduction than it actually was when presented to the microphone. If you have two microphone preamps that are otherwise identical but one has more gain than the other, the one with more gain will be noiser even if the signal to noise ratio is exactly the same. Said another way, if you turn up the gain enough on any signal chain you will hear the noise. Physics says it will always be there at room temperature.

What's important is that signal-to-noise ratio is exactly that--a ratio. Imagine the sound level someone playing a trumpet directly into your ear. It will be painfully loud, certainly in excess of 100 dB SPL. Place a microphone at that point and use a recording system with 80 dB signal-to-noise ratio. If the trumpet is reproduced at 100 dB SPL by your speakers, you can be certain you will never hear the noise in your ideal listening environment. Now, put on your set of headphones and adjust the volume so the trumpet is at 100 dB SPL. When the trumpet stops playing you will not hear the room noise because you have reduced the volume of the trumpet from it's natural loudness that close to your ear, down to 100 dB. You can now only hear the noise if you turn up the volume, either on the microphone or your headphones. Once you change the gain, you have effectively reduced the signal-to-noise ratio by the same amount as the gain increase.

Remember, it's a ratio. In real-world recording you are almost never requiring anywhere near the 96 dB signal-to-noise ratio made available by 16-bit PCM recording. The "almost" here only applies to recording very quiet sounds: breathing, clothing rustling, the breeze blowing through grass. And even then there's no challenge unless you want to hear the sound you're recording played back actually louder than it was when recorded. In a single sentence: If an actual sound is (for example) 50 dB SPL, reproducing it accurately cannot require a signal-to-noise ratio greater than 50 dB to create a recording with inaudible noise.

Yes, you'll hear the hiss when you turn up the gain. And using very low-noise mics and preamps can reduce it, certainly, but only by a little bit. You have to keep it in perspective. Quiet sounds will almost always be played back quietly, not loud in your phones. In the final analysis, the difference in noise levels between moderately priced audio equipment and the most expensive available will only be audible in a small number of real-world cases, if any. Chasing SNR is going down a rabbit hole.