Horst Mohr and a few others in our Digest group have built music roll
readers using discrete photodetectors which replace the hoses and
pneumatic sensors in a "tracker bar" reader.  The "Optical Scanner"
machine is a video system with no tracker bar.  Wayne Stahnke has
demonstrated that both methods are capable of recovering all of the
critical detail and timing from a music roll, with sufficient precision
that a "hole for hole" duplicate can be perforated.  The primary
advantage of the optical scanner "camera" is that it can easily be
adjusted to scan any format of music roll, in any size.

If you wish to build a reader for music box disks you should contact
our member Ron Yost, who built a reader using fiber-optic strands to
couple the separate photo-detector array to the light at the holes of
the tracker-bar.  This method would accomodate the close channel
spacing of the music box disk.  I've seen photodiodes of 0.080-inch
diameter, but I don't know if smaller devices are readily available.

I once saw a 36-inch music box disk; it seemed gigantic!  How many
channels does it have?   Some styles of disks have a metallic
projection on the rear side.  Won't this create a problem in an optical
reader?

{Jody, can you provide the current address for Ron Yost?}

 [ I'll let Ron do that.  Jody

Best regards,

• ----------------------------------
|         Robbie Rhodes            |
| Return-Path: rrhodes@foxtail.com |
 ----------------------------------