BEHRINGER TUBE ULTRAGAIN MIC200 Microphone Preamplifier

This is a BEHRINGER tube microphone preamplifier.

I purchased it at a flea market on April 23rd.
I was told that the previous owner bought it new from Sound House in 2017, used it about once a month, did not power it on except when in use, and then put it away because they stopped using it for a while.

I have used it for about 2 hours myself.

I experimented with it to see if I could eliminate noise from my specific microphone setup, but while I was able to increase the volume, the noise also increased, and I didn't feel much difference, so I am selling it. It's possible I just couldn't master it.

This was my first time using a vacuum tube, and I had never used a preamplifier before, so I don't know if the noise in my specific setup just got louder, if the product itself has noise, or if this is how preamplifiers are supposed to be.
The noise sounded like the original ambient noise getting louder with the increased volume, not like a different sound being generated.
Since I am not knowledgeable about this, please consider it as-is (junk).

For operation check, I have confirmed the level meter, buttons, volume knobs, sound output, and volume increase/decrease.

Please read this carefully and purchase only after understanding.