The Super soul and soul both are unchanged.
The difference is that in material contact, the soul appears to be changed.
But the Super soul is not affected by material contamination; therefore there is no sign of change.
The change of soul is like that water becomes ice in contact with refrigerator.
And as soon as there is temperature the ice again becomes water.
Similarly the changing nature of the soul is just like change of water to ice.
The tendency of ice is to melt and become water again.
So due to contamination of matter, the soul by illusion identifies with material existence.
But the tendency is to melt again to Krishna Consciousness.
So when there is sufficient temperature in contact with bona fide Spiritual Master and devotees,
the soul again becomes Krishna Conscious, like the water.
The difference is that in material contact, the soul appears to be changed.
But the Super soul is not affected by material contamination; therefore there is no sign of change.
The change of soul is like that water becomes ice in contact with refrigerator.
And as soon as there is temperature the ice again becomes water.
Similarly the changing nature of the soul is just like change of water to ice.
The tendency of ice is to melt and become water again.
So due to contamination of matter, the soul by illusion identifies with material existence.
But the tendency is to melt again to Krishna Consciousness.
So when there is sufficient temperature in contact with bona fide Spiritual Master and devotees,
the soul again becomes Krishna Conscious, like the water.
Srila Prabhupada letter, November 12, 1968