Atmasphere,
It surely cannot be true. Perhaps you or Al can elaborate, but overloading is a function of the cartridge's output AND the phono stage's gain/sensitivity setting, isn't it? Theoretically, you could probably overload with a low output MC cart if you have a gain mismatch large enough. From your post, it sounds like you can only overload with MM carts.
The issue is can a cartridge of 1.05 mV or so overload a phono section set up for a low output moving coil cartridge.
1.05mV is about 6 db more than 0.5mV which is considered low output. That represents a doubling of voltage from 0.5mv to 1.05mV.
If that 6 db is making a difference in the overload of the phono section its overhead is poor. That is the long and short of it. In our phono section which works with 0.2mV, it cannot be overloaded by a high output 5mV cartridge.
55db is on teh low side as low output moving coil phono sections go; we have 60 db (I am of the opinion that you don't need that much gain if your circuits are low noise).
So I really think that you need to look at loading and the setup of the cartridge in the arm- its very likely that some other factor has been overlooked. IOW I am sure you are hearing something but overload of the phono section isn't (or shouldn't be) it.