Consistent stylus depth without advance ball - Neumann?

[audadvnc]

I cut on a Scully lathe using a Westrex record head which incorporates an advance ball to establish the stylus cutting depth. I understand how that mechanism works, but have never seen a Neumann lathe in action.

How do users of Neumann lathes set a cutting depth without a track ball? Is the head on some sort of machine-controlled pivot? What drives the cutting depth - a moving coil similar to the cutting coil? How does the machine take disc non-flatness into consideration, and avoid varying groove depth on blanks that are not ideally flat?

Is this machine-controlled pivot (if there is one) also used to control the variable depth functions, or is that handled by DC bias applied to the record head coils?

[opcode66]

Yes, you have it. The cutterhead attaches to a plate on the front of the suspension box. The plate can tilt. The tilt is governed by both a moving coil and a tension spring. The suspension box also has a dashpot to dampen vertical movement.

There is a potentiometer on the front for adjustement.

It is assumed that the blanks are flat. That is sort of why we pay so much for lacquer discs. They are supposed to be flat and free of imperfections on the preferred side.