The answer is most-likely lies in integration between cartridge and phono preamp if the unit functions OK. The variable gain settings in many cases cannot be done successfully since it may cause gain stages go out of stability i.e. oscillate. Selecting a best fixed gain and eliminating this flexibility feature could result in vast performance improvement(some small surgery required)
Gathering opinions on this post you may find folks who are more or less tolerant to the noise you're describing, but to be more precise in best gain value you must consult manufacturer who probably has knowlege about the best gain value i.e. with minimal vulnerability to oscillation and maximum stability and performance certainly with no exception to suggest inspecting the unit for possible service.
Gathering opinions on this post you may find folks who are more or less tolerant to the noise you're describing, but to be more precise in best gain value you must consult manufacturer who probably has knowlege about the best gain value i.e. with minimal vulnerability to oscillation and maximum stability and performance certainly with no exception to suggest inspecting the unit for possible service.