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Domestic Beta Audio Systems


As indicated under the section "what machine do you need?" there are three types of audio recording systems used on beta domestic machines, mono, linear stereo and HiFi stereo. All tapes recorded on beta video machines have a linear sound track which runs along one edge of the tape. They also have a track on the other side for synchronising the machines capstan and video head speed phases, to record and recover the tapes diagonally recorded picture information. An early audio design change to create a stereo record and playback capability, divided the linear audio track into two parts plus a guard band to ensure channel separation. Some disadvantages of linear stereo were that alignment was made more difficult and tape damage affected the audio to a larger extent, particularly the sound channel at the extreme edge of the tape.

Less track width meant a worse signal to noise ratio, so Sony also introduced a "beta noise reduction" (BNR) system which was similar to the Dolby audio system used on cassette tapes. I believe the later Sony mono machines such as the SLF60 had the hi/low audio switch option added to roughly compensate for this high frequency emphasis during playback when necessary.



Compatibility - A design flaw with linear stereo audio?


The linear stereo concept works fine as long as the tape is played back on a linear stereo machine. However, if the tape is played back on a mono machine, unless the audio heads' azimuth alignment is exactly the same as that of the original recorder used, then phase cancellation can occur by incorrectly combining signals from the right and left channels. Indeed even with a correctly aligned machine, equal level same frequency signals on the right and left channels but with opposite phase to one another will cancel out. The ONLY solution to the linear stereo phase cancelling problem is to ALWAYS use a BETA LINEAR STEREO VCR to play back LINEAR STEREO TAPES.



Beta HiFi Stereo


A later engineering development saw the addition of two HiFi heads to the video disc thus allowing recording of the stereo audio channels, with azimuth offset for separation, along with the video signal using the wider bandwidth diagonal recording technique. HiFi recorders still retained the linear mono audio head and tracking control heads. Beta Stereo HiFi VCRs almost rivalled CDs for their sound quality. As a marketing strategy, the stickers used on Top of the Sony SLHF100 and SLHF150 machines compared the performance of the various audio systems then available.

See http://www.palsite.com/100ovi.html



A "Professional" Beta Audio System


Sony developed a pulse coded modulation (PCM) system which used the Beta VCRs video system to record high quality stereo audio in the manner of a CD. There models developed for this system were:-

  • The PCM701 which had dual ADC's.
  • PCM-601 had the advantage of S/PDIF digital I/O.
  • The PCM-501ES and
  • The PCM-F1.

See http://www.palsite.com/pcmf1ovi.html



Also note the PCM-F1 marked the first appearance of Sony's CX-899 ADC and 890 DAC chips. The latter was subsequently used in Sony's first CD player, the CDP-101.