[Jukebox-list] 1939 Seeburg Amplifier Tone

Hope everyone had a great July 4th weekend! I recently rebuilt a 1939 830-Z1 Seeburg amplifier and it works but the complaint is that the tone is too tinny and the bass control makes no difference when you adjust it, treble adjustment is good. The cartridge is an Astatic N51 and no modifications were done to the amplifier as I was under the impression that this amp worked well with this cartridge. Is there a recommended mod for this cartridge that I’m unaware of ? If not how would I tackle this issue? As always Appreciate the help, Mauro