More hours for sure on the unit but you should start to hear more definition as the tubes start to burn-in around 75 hours and will continue to improve as well as the circuits. A Mullard Square Getter and a fuse change will also improve things quite a bit...
Also, try turning the unit off for 15 mins and back on for the next couple of days.
Wig
Also, try turning the unit off for 15 mins and back on for the next couple of days.
Wig