That's great to hear. FYI the Dynavector Cartridges prevalent at the time of the 501/507 series launch were medium compliance.
You can get more performance from your 501 by fine tuning the position of the rear counterweight.
If you take off the anti-skate, lift the cartridge ( or remove platter ) try blowing on the arm. When the rear counterweight is at its optimum you should be able to move the arm back and forth by gently blowing on its side. When you see this you start to understand the rationale behind the arms split inertia design. Effectively when properly set up the arm floats in the horizontal domain.