Thanks Stephan for borrowing me the device. The following tests are all USB powered BUS POWER with no AA batteries inside.

I’ve asked the audioengineering Reddit community and they removed my post.

A Youtube link from Stephan informed me that the DR-40 suffers from high noise preamps, resulting in a high noise floor.

Solution: I’m not sure yet. Post processing?

Lowcut filter 40Hz

Lowcut filter 80Hz

Lowcut filter 120Hz

Lowcut filter OFF

With no Inputs

Alarming noisy... white noise? How does one get clear audio straight out of a recorder?

With batteries

I.e. no BUS POWER, 3 fresh Alkaline batteries

With no inputs

It’s very similar to Julian Krause’s test here https://youtu.be/ZvqQ2ejq6og?t=487