I'm afraid it still sounds like you have a problem with your installation – the fact that you can turn the Orville down 30dB and still hear any signal means that you have a lot of gain after it – this is why you hear the noise.
You need to set things up so that a full level signal into the Orville lights all the meters. Then, turn down the gain on whatever the Orville feeds (this must NOT be a mike input) as much as possible. Only then should you consider turning down the Orville output gain.
What is the Orville actually feeding ?