Hello there. I am using Cubase 12 with the Yamaha AG06MK2 audio interface. I’ve been getting a constant low signal (around -80 db) from “stereo in” for quite some time now, even without inputs connected, and have no idea how to get rid of it. It started all of a sudden back when I was using Cubase 11 with an older audio interface. After updating to Cubase 12 AND changing my old Yamaha to the newer mk2 version, the problem still persists. I have tried different drivers as well, like “Generic Low Latency ASIO”(switching from the yamaha input to my usb headset mic - still didnt solve the problem, so the audio interface clearly isn’t the culprit), or “ASIO4ALL” (also to no avail). Is this just a software glitch/ driver conflict? Any idea if it can be fixed? I think I should also mention that the problem is non-existent in my other DAW - Studio One, which doesn’t use ASIO drivers.
Here’s a screenshot of what’s going on. You can see it in the mix console’s meter:
Is the gain on your interface channels turned up? That looks like standard self noise.
Thanks for your reply. No, the gain is not turned up…Like I said, the problem still persists even when turning the audio interface off and switching to my headset microphone, which is directly connected to my pc through usb.
Is there a plugin enabled in the input strip?
Nope.
You have “monitoring” enabled on the “audio 01” track. Switch that off and there will be silence 
It is normal, as @Dunk79 already wrote, standard good old analog self noise. I have that on my RME, too.
Check your Audio Connections when you switch off your main interface. Cubase will then use the Generic Low Latency driver, and probably automatically mapped one of your computer’s microphone inputs to the “stereo In” bus. If you set the device port for the “stereo in” to “not connected”, you will see that the noise vanishes.
Really? I get around -100dB on RME’s analog inputs.
The 3rd from left has a microphone connected,
the two channels on the right have synths (switched off) connected; the audio cables catch some noise
Well yes, the noise will obviously vanish if I disconnect the inputs via cubase and I am aware that analog gear can produce that kind of noise, but the problem is that it didn’t use to do this in the past. All I can think of is that the noise appeared while having my electric guitar connected to my old audio interface (which has a built- in guitar amp that can be controlled by a software). I managed to record it cleanly for a while, but suddenly this signal occurred and never really went away ever since…Still, I’m not sure if it’s actually related to the issue to be honest…
I got a new interface thinking it might be a hardware problem, also got a new version of cubase, but nothing helped…
I would imagine a headsets self noise is greater than your audio interface, TBH. I’m guessing though as I’ve no idea what you have.
Is the noise audible? How would you describe the noise? (Is it a hiss? A low rumble? A digital whine?) Does it get recorded as audio if you press record on Cubase?
Well, depends on how much you crank the input gain, of course. With the MIC gain at 0, I have -100, too. Increase the gain, noise unsurprisingly gets “louder” (I still don’t hear it, that starts at 50dB and more…).
This is what I was referring to in my first post. That’s the self noise of your interface. You don’t need anything plugged in to hear it. If you have the input gain turned up, it amplifies it.
Yep, exactly. And frankly, -80dB is not much of a problem… If you record electric guitar, that is noisier. When recording with a microphone, most likely your environmental noise is louder.
The f****** tinnitus in my head is louder 
Ah yes … I too have the soothing sound of the ocean … even though I live 20 miles inland! Grrr… 