Very few Betas are equipped with linear stereo. This added capability was mostly limited to the Sony professional Betas, models that included the GCS-50, SLO-323, SLO-325, SLO-383, SLO-420 and the SLO-1400 and SLO-1800 production duplicators designed for replicating studio movies, music videos and instructional materials. The GCS-50 and SLO-1800 were also SuperBetahi-fi stereo models. The GCS-50 was the only SuperBeta model that permitted recording separate audio information on the two linear tracks independent of the Betahi-fi stereo. The SLO-1800 professional duplicator was originally released with linear stereo audio tracks in addition to the Betahi-fi. Presumably this was done to accommodate the Marantz VR 200 which was introduced just prior to Betahi-fi. Sony later changed the SLO-1800 and removed the linear stereo. This was done to save cost and because so few consumer machines would actually use it. This didn't exactly thrill Marantz. They never introduced another Beta with their name on it. (The VR 200 was made for them by Sanyo.) Linear stereo is recorded by two, stationary stacked audio heads located at the upper area of the ACE assembly where the top edge of the tape goes by. ACE is short for Audio, Control pulse and audio Erase. These pick ups in the ACE are just like in a reel-to-reel audio recorder. A magnetic signal is recorded on or read from the tape as it travels past these stationary electromagnets (or heads). In regular monaural recording there would only be one single audio head. Betahi-fi stereo on the other hand, is recorded elsewhere. It is in placed the picture being recorded by the spinning video heads. This was accomplished by making a slight alteration in the video signal called reformatting. The luminance part of the broadcast signal was move up slightly (400 MHz) to make a space was available for inserting four FM carriers for recording stereo sound. Two carriers tracks for the left and two for the right channel. Duplication of the channels assured that any tape flaws would be accounted for. As long as everything stays in place the FM doesn't disturb the video information. Due to the high speed of the spinning heads this system produces nearly perfect stereo. The FM carriers are going by at a very fast 30 inches per second so annoyances like wow, flutter and tape noise are virtually eliminated. Beta could do this because of its bigger video drum which produces a longer, stronger, cleaner, fuller magnetic signal than did VHS. Their system could not duplicate Betahi-fi because there wasn't enough room in its video signal to insert any additional information. Their small drum cramped their video so they had to resort to imbedding* their audio to get similar result as Betahi-fi but it was an add on and it performed well as long as the tape was new and not played too much. To open a panel on the possibilities when using linear stereo click here. To go back to the description page click here.
*Imbedding was a method used by VHS to duplicate Sony's Betahi-fi stereo process. This method also took advantage of the high writing speed of the video drum to produce decent fidelity. With this system two additional audio heads were added to the spinning drum. These extra analog heads were in addition to the existing video heads or any trick heads used. These heads recorded two analog signals just before the video heads came along and recorded over it. It worked because the two types of signals were magnetically different from each other, plus the video heads didn't completely erase the previous audio recording. When played back the video circuitry read the picture information and the spinning audio heads saw the analog. Alignment was imperative with this system in order to get to cooperate. That was mostly accomplished by the placement of the various heads in the drum during its manufacture. Since the two magnetic signatures are different they can be adjusted separately. In practice the audio particle strength and penetration had to be deep so the video didn't erase it. This required high quality video tape. This strong magnetic force could cause distortion and this had to be accounted for in circuit processing. The audio could weaken over time and could eventually disappear. For this reason stereo was also recorded by the VCR using twostationary linear heads located in the ACE assembly. If the hi-fi should fail the VCR would automatically switch to the dual linear audio tracks as a back up. This was especially helpful for rental facilities where the tapes got a lot of plays. |