In simplest terms, a magnetic instrument pickup
consists of an insulation coated
copper wire coil wound about a magnet assembly, or placed in close
proximity to a magnetic field. The ultra-fine coil is built up over
thousands of turns, and is often contained within a bobbin.
To add to this simple description, the magnet assembly is often provided with some form of insulation to further isolate it from the coil windings. This 'added' insulation may take the form of lacquer, tape, or a molded plastic bobbin. Further comments about magnet/coil insulation may be found on the 'Questions' page.
For general introductory purposes, the above description will suffice.
Further information can be found at GM Arts Pickup
Pickup winding usually requires the bobbin to
and draw hair-fine coil wire about it. Alternatively, a feed system
be contrived to wrap the wire about the stationary bobbin, thereby
replicating the motion of winding entirely by hand. However, the former
is more common where the bobbin is rotated by a machine which is linked
to a 'turns' counting device. During such winding operations, the
wire is drawn under controlled tension exerted by hand, or a machine
tensioner. For those looking for a 'step by step' handbook to create
such a machine, Jason Lollar's Book, 'Basic Pickup Winding' (see
update notice below) will
prove informative. This web site offers other suggestions for those
some engineering skills and a little inventiveness.
Update: April, 05. Jason's book is no longer published and therefor unavailable, but his web site does offer other information.