UR22C Strange Noise

I am using an UR22C since a few weeks and have some issues with the noise.
I made some screenshots to document my findings.
Both inputs are without any connection, PhantomPower off
When I slowly turn the gain knows from far min to max I suddenly get a “lot” of noise. This strats at about the 3 o’clock position and is for both inputs.
My cubase11 levelmeter shows a peak value of -55.4

Switching on the Hi-Z for input 2 I get a peak value of -44.5

My UR22C Setting: Samplerate 48000 kHz
Mode Standard
Buffer Size: 128 Samples
UR22C Software-Version:
Boot V1.00
Main V1.50
Driver V2.04
dspMixFX UR-C V1.5.0

PC Windows 10 - 64 Bit /I7-7820X/64 GByte-Ram

Any idea what is going wrong here?
In the worst-case scenario (Noiselevel -44 dB) from the 32-Bit resolution I get 7.5 Bits for my signal the rest is just the sampled noise.
Am I alone with this problem ?
Many thanks in advance to share your ideas / hints / with me.!

This is not a good way to test the preamp noise. Ideally you need a dummy load to test it properly.

You have nothing connected… the behavior will change if you connect real gear

No, this is wrong…
You have to take signals into account and not only the noise…
a normal studio microphone will produce sufficient levels with the gain knob at 10-12 o’clock position

Hi misohoza and st10ss and thanks for your comments.
I tried what you told me:
Used an AKG P3S (Dynamic Microphone)
Here the values from the Datasheet
Sensitivity 2.5 mv/PA (requires a lot of gain for a good recording level)
typically I have to set the gain-knob between 3 - 4 o’clock.
recommended Impedance >2 kOhms
Connected to the inputs the noiselevel improved somewhat. Now I get -61.7 dB with the maximum Gain.
Used 2 Rode NT5 (matched Pair) with PhantomPower on
These microphones are more sensitive 12mV/PA
Signal to noise of the microphone 78 dB
Impedance 100 Ohms
With these microphones I cannot measure the noiselevel with the max-gain-Setting as my
environment noise (I am a Homeplaye) is too noisy. But I guess I get a pure interface-Noiselevel similar to the one with the AKG.
So I ask myself: What are the 32-Bit resolution good for, when most of the resolution is just for the
self generated noise of the interface.

BTW. I have also an “old” Focusrite Saffire 40, With that I have noiselevels < then -80 dB.

This was my expectation for the UR22C too.
So I think I have to live with that.

Again many thanks for your comments.

as far as I remember the Saffire has a maximum gain of 55dB and the UR22C has a bit over 60dB and the gain ranges differ… so this is not really comparable