Right match

@rucan65

What is your source? Are you using an output of a turntable connected to a line level in on the musical fidelity preamp?
Luxman has a built in phono stage…that’s the only explanation I can find other than your preamp is broken. 

I get it. I was asking what your source is and whether or not you have your turntable directly plugged into the m8 preamp 

If the M8 is a line stage only or you have your turntable plugged into a line level input or you have a low out MC cartridge and you have your phono input set to MM you would experience what you’re describing .

Matching pre to amp you use pre output impedance and amp input impedance 

Also, your M8 output impedance is 47ohm and a perfect match with your amplifier’s input impedance of 50kohm.

What cartridge is on your turntable?

There is a switch on the back of M8 that toggles between MM and MC.
Like I said if you are using a turntable, make sure it plugged into the phono input on the back of M8, it is grounded to the ground screw, and the MM/MC toggle switch is set according to the type of cartridge you’re using. So tell us what cartridge it is. Or just try flipping the MM/MC switch to MC. Report back what you’re hearing. 

Break in wont fix what you’re describing. Have you read the manual? Have you contacted the dealer or seller that sold you this preamp to attempt to troubleshoot it over the phone?