
My new toy. This is a 1982 vintage broadcast video recorder. I know these machines inside and out. I have many concerts and the like copied from edited masters. Some are Dolby A encoded and I have a CAT 363 decoder to go along with it.
This is a four motor transport using brush type DC motors, two reel motors, the capstan, and video head durm. Each motor is under servo control. The tape tension is controlled extremely accurately - it has to be to meet broadcast specs. These servo systems are also interlocked to each other. The capstan is belt driven as direct drive is not as smooth. But Ampex did abandon the belt drive on later models.
Audio performance is quite good, three channels 50-15K but it can go a bit wider. 50-15K was/is NTSC TV proof of performance. A lot of these concerts are mixed down from 16 or 24 track direct to the video master so they are on par with studio audio masters.
However there is a drawback to really good audio. The complex servo and control systems generate all kinds of clocks and other pulses right inside the audio spectrum. The power supplies are also exposed to this junk. So I plan to do an external tube based preamp just like the Tape Project. The internal audio system is good, but an outboard tube preamp should be a welcome improvement.
These machines are "direct color high band" recording. This is leaps and bounds above the home VHS format. The machine captures the entire NTSC spectrum from DC to 4.2mhz at around 48db video S/N. Unlike DVD it is also an uncompressed analog recording. Uncompressed video has a distinct quality difference from DVD just as LPs and analog tape has from CDs. And while most movies are transferred to DVD from film via component video, these live concerts are forever locked into the NTSC composite format. So my tapes will always be superior to a DVD of the same concert as the DVDs are made from the same source but are also compressed video.
For those not familiar with analog video recording, the raw video signal is not simply mixed with a bias and put on the tape as is the audio. That would require a 17 octave spread on tape with the all familiar 6db per octave loss. That means an equalizer with a 106db gain spread - impossible to make! So the video modulates an FM carrier from 7.09mhz to 10mhz. This is now less than an octave spread and can be easily equalized. Of course we still need a head to tape speed of 1000ips to lay down a 10mhz signal on the tape. VHS and Betamax machines used a much lower FM frequency due to the much slower head to tape speed - about 400ips. So in turn the incomming video must be rolled off to less than 3mhz thus substantially reducing image detail. Color must be seperated in VHS as well and recorded at an even lower frequency which creates the poor S/N ratio we had with VHS.