Needle vs. Laser

In the past 100 years approximately 30 billion phonograph records were produced and sold. Still, the problematic method of playing a record using a diamond chip needle secured to a metal cantilever that moves a motor (moving coil or moving magnet) is still the common method of playing a record. Mechanical reproduction is fraught with “compromises” that limit the ability to play a record faithfully and accurately. Each time a record is played there is some damage and wear to the record.

It is important to note that none of the restrictions and limitations mentioned in this article relate to the laser playback method used in the ELP Laser Turntable. This article can be of value in setting up your playback system if you do not own a Laser Turntable.

The Archivist’s Dream Machine

Most styli that are available on modern phono cartridges will not yield good results. The groove geometry varied greatly on early recordings. The stylus used on cutters may have been narrower than later recordings, or wider. You must match the stylus to the exact shape and depth of the original record. Many engineers that specialize in restoration of rare recordings have special styli manufactured for the specific record. Often, these elliptical styli are ordered with truncated tips so the needle will not reach the bottom of the groove where heavy damage, noise, and dirt may lie. This is not necessary with the LT because the optical system finds the shoulders of the groove and sets the microprocessor to the width of the groove.

The image below shows how the LT reads the audio from the grooves.
There are some types of records the LT will not play.

  1. Scratch damage on the land area of grooves.
  2. Laser beams that read the audio modulations.
  3. The area of the groove that is read avoids the scratch.
  4. The area of the groove where stylus damage is found.
  5. The Groove with damage from a needle.
The laser beams must reflect from an opaque surface in order to be read. Clear or colored records are transparent, or translucent, and will not reflect light to the sensors. Other types of records that may have difficulty.
Flat Picture of LP Grooves taken by electron microscope (magnified 250 times)

 Reflection Angle of Laser Transferred into the Sound

  1. Vertical cut records like the early Edison “Diamond Cut” series. The modulation is up and down rather than lateral. The code pbad is displayed in the message window.
  2. Rounded groove shoulder. The code rbad is displayed in the message window.
  3. A groove with a rounded bottom produces distortion.