can you add tone controls to a primaluna HP integrated amp

I tried a Schiit Loki in the tape loop of my Pass XP-22 and it just killed the sound. Both the volume and resolution dropped. It may be due to my having XLR connections everywhere else. I suggested to Schiit that they provide XLRs. I only tried the Schiit as a solution for my vinyl source. I’m using the vastly superior Roon with DSP for digital. In my room my Vandersteen 5a Carbons sound too bright in the midrange at times. So I created a mid shelf DSP setting exactly matching the crossover points and 6db slope of the midrange driver. I created three versions with 1, 2 and 3 dB down levels. It works wonders at times. For the analog side, the best I can do for now is to run my MC cartridge load down at 100 ohms. I wish I had a much bigger room.