A few other things to consider: try using a monaural signal path
utilizing a single loudspeaker for auditioning the final material. The
complex phase relationships that occur when using stereo equipment
(especially two speakers) can be the cause of some serious errors.
To my ears there is a vast difference between two speakers and one speaker for monaural listening. 78s were all monaural and practically all listening was with a single sound source. Putting the 78 sound through two sound ports changes the medium.
Unfortunately hardly anyone will listen to the restored sound through a single channel. So what do you want your monitor to show: the sound of the 78 or the sound people will hear?