Hi, I honestly have no knowledge about this "Souther" Cartridge you have, and as nsgarch explains, it's probably unlikely that it is a high output MC Cartridge. (Due to the fact that you seem to have sufficient gain, and you don't mention that you have to crank the reciever's volume control really high to get acceptable volume levels)
Most MM Phono stages in older recievers generally accepted-were compatible a MM Cartridge with output between 3.5Mv-5Mv.
Even let's say if you were running a high output Benz Micro Glider (Like I myself have) with an output of 1.8Mv, I think you would find insufficient volume, and a drastic mismatch of volume levels versus other outputs (ie: FM, Aux, etc) on your reciever.
There may be the possibility of finding a model number of this Cartridge by unscrewing it from the headshell, and looking in between, on the Cartridge's topside?
Once you could possibly find this out, more information would be likely to be known about it.
Hope this helps, enjoy! Mark
Most MM Phono stages in older recievers generally accepted-were compatible a MM Cartridge with output between 3.5Mv-5Mv.
Even let's say if you were running a high output Benz Micro Glider (Like I myself have) with an output of 1.8Mv, I think you would find insufficient volume, and a drastic mismatch of volume levels versus other outputs (ie: FM, Aux, etc) on your reciever.
There may be the possibility of finding a model number of this Cartridge by unscrewing it from the headshell, and looking in between, on the Cartridge's topside?
Once you could possibly find this out, more information would be likely to be known about it.
Hope this helps, enjoy! Mark