Laser turntable
From Wikipedia, the free encyclopedia
A laser turntable is a phonograph that plays gramophone records using a laser beam as the pickup, rather than a stylus in mechanical contact with the disc. This has the advantage of not mechanically wearing the disc in playback.
Present laser turntables play most varieties of phonograph record (vinyl or 78 rpm) at high fidelity. Being quite expensive — over US$10,000, comparable to the very best conventional turntables — they are favoured by record libraries and radio stations (for archival use and transcription to digital media), and audiophiles with extensive personal collections.
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[edit] History
The laser turntable was first conceived of by Robert Reis and Robert E. Stoddard, both graduate students at Stanford University. Upon graduation Reis and Stoddard established Finial Technology and started development of an optical turntable. Their first working laser turntable was completed in the late 1980s, although the first examples were not of usable audio quality (having tremendous problems with dirt and dust on records) and the company lacked the technological and commercial experience to proceed, leading to Stoddard and his team joining the Japanese company ELPJ.
[edit] Technical details
The laser pickup uses five beams — one on each channel to track that side of the groove, one on each channel to pick up the sound (just below the tracking beams) and a fifth to track the surface of the record and keep the pickup at a constant height, which allows for record thickness and any warping. The pickup focuses on the groove above the level a physical stylus will have travelled and below the typical depth of surface scratches, giving the possibility of unworn reproduction even from worn records. The pickup output is analogue rather than digital. The main limitation of the pickup is that the record must be black and opaque — coloured, transparent or translucent records may not work.
Use of a laser pickup avoids many problems with physical styli: physical wear, horizontal tracking angle error, leveling adjustment issues, inner groove distortion, channel-balance error, stereo crosstalk, anti-skating compensation, acoustic feedback, locked-groove problems, problems tracking warped, cracked, or eccentric records and cartridge hum pickup. The laser diode also typically lasts 10,000 hours of playback, rather than the 500 hours recommended for a diamond stylus or 50 hours for a sapphire one.
Versions of the ELPJ laser turntable will play back analogue disc records at any speed from 30 to 90 RPM and of any size from 7 to 12 inches (178 mm to 305 mm).
[edit] Competitors
Experimentation is in progress in retrieving the audio from a record by scanning the disc and analysing the scanned image. If developed sufficiently, this may make the laser turntable obsolete in the future.
[edit] External links
- ELPJ - About the laser turntable
- Record scanning - Ofer Springer
- Record scanning - Sound Reproduction R & D Home Page
- Record scanning - VisualAudio: An optical technique to extract sound from old records
