Fitting a cutting stylus to a Neumann cutting head.
Assuming that there is already a stylus present, switch the cutting amps out of operation. Then gently remove the multipole connector to the right-hand side of the cutter head and the helium feed.
Due to the magnetism of the cutter head, you may want to (a) remove your watch (b) ensure that you exclusively use the same tools for this purpose. Remove the lid of the suspension box using the knurled knob on the top. Whilst supporting the cutter head, using a large screwdriver undo the bolt securing the head in place, enough to release the cutter head.
Ease the head away from the suspension box and place into the stylus changing microscope. Undo the heater wires from their terminals by pressing down on the top of each terminal in turn. Using the stylus removal tool, gently ease the stylus out from the torsion bar, by swivelling the stylus from side to side and very gently upward pressure. Do not use the torsion bar to provide leverage!
Carefully remove the stylus from the packaging that it is shipped in and gently tease wires out to their full length ensuring that they are extending from the front of the stylus. With the wires pointing toward the brass terminals of the cutter head, gently place the shank of the stylus into the hole in the torsion bar. Then looking through the microscope, adjust the stylus so that the flat, back of the stylus is parallel with the end of the torsion bar / microscope graticule.
It is important to look at the stylus, not at the metal plate of the shank as these may not be aligned. In addition, check that the tip of the stylus is still aligned as it is possible for tip to be slightly twisted, in which case align to the tip. Once happy, firmly, but not roughly seat the stylus into the torsion bar, then check once more that everything is still aligned.
Next attach the heater wires to the brass terminals, there are number of things to be wary of. The wires must not be tight, otherwise they will act like a guitar string and cause resonances. It is also important that loop of the wires you have created do not touch each other, or the cutter head assembly. Personally, I always like to trim off the excess heater wires lest they touch the lacquer, the cutter head, or short out with each other.
Finally place the cutter head back into the suspension box. Place the metal bar supplied with the microscope flat upon the turntable, move the cutter head over the bar and ensuring that the stylus will not be damaged, lower the cutter head onto the bar and ensure that it is parallel with the turntable. Tighten the bolt to hold the head in place, attach the multipole connector, replace the suspension box cover, and switch the cutting amps to operate.
Cut and trace to adjust the heater current and to adjust the depth, checking that the faceplate where the cutter head is attached, is flush with the front of the suspension box.
When changing a stylus, it is also essential to carry out a series of noise tests by cutting bands of unmodulated grooves with the heater current set at 4.0 or even less. Increase the current to 4.25, 4.5, 4.75, 5.0 and finally 5.5. After examining the grooves through a microscope play each band noting which level of current produced the optimum sound level.
This procedure should also be carried out when you change Lacquers discs from one batch to another.
A big thanks to Barry Grint (Air Studios) for sharing his considerable knowledge and experience in putting this article together.