I think I read that most of the pioneering digital formats for sound were arranged around cine film and hand editing. If correct the edit would be possible every 4 frames. Doubtless a visible marker for the ideal cut point. I believe there were no real world versions of this.
I have always wondered if optical digital would have been possible. The valves were fast enough. It might have been like better AM radio in bandwidth with grater clarity. Digital theory was known.
I have always wondered if optical digital would have been possible. The valves were fast enough. It might have been like better AM radio in bandwidth with grater clarity. Digital theory was known.
I don't know if this is relevant for your discussion, but the Bell System Technical Journal has articles about digital telephony from 1948 and about digital television from 1951 (experimental closed-circuit television, but still...). I particularly like the photos of the analogue to digital converter cathode ray tube in the 1948 article.
W. M. Goodall, "Television by pulse code modulation", BSTJ January 1951, pages 33...49
BSTJ 30: 1. January 1951: Television by Pulse Code Modulation. (Goodall, W.M.) : Free Download, Borrow, and Streaming : Internet Archive
L. A. Meacham and E. Peterson, "An experimental multichannel pulse code modulation system of toll quality", BSTJ January 1948, pages 1...43
BSTJ 27: 1. January 1948: An Experimental Multichannel Pulse Code Modulation System of Toll Quality. (Meacham, L.A.; Peterson, E.)
W. M. Goodall, "Television by pulse code modulation", BSTJ January 1951, pages 33...49
BSTJ 30: 1. January 1951: Television by Pulse Code Modulation. (Goodall, W.M.) : Free Download, Borrow, and Streaming : Internet Archive
L. A. Meacham and E. Peterson, "An experimental multichannel pulse code modulation system of toll quality", BSTJ January 1948, pages 1...43
BSTJ 27: 1. January 1948: An Experimental Multichannel Pulse Code Modulation System of Toll Quality. (Meacham, L.A.; Peterson, E.)
Digital electronics pre-semiconductor was not exactly practical.
My school was offered a retired Pegasus computer in 1968 from the Royal Aircraft Establishment in Farnborough England. It filled two shipping containers. The school backed out when they realized what the electricity bill would be ... but even MORE quickly backed out when they discovered they would have to replace dozens of valves (tubes) every WEEK as they would fail with cathode poisoning by being turned off for at least 50% of the time!
Semiconductors made it good.
My school was offered a retired Pegasus computer in 1968 from the Royal Aircraft Establishment in Farnborough England. It filled two shipping containers. The school backed out when they realized what the electricity bill would be ... but even MORE quickly backed out when they discovered they would have to replace dozens of valves (tubes) every WEEK as they would fail with cathode poisoning by being turned off for at least 50% of the time!
Semiconductors made it good.
Well, they helped the British to decipher messages straight from Hitler in the second world war, which seems quite practical to me.
Anyway, I'm surprised cathode poisoning was such an issue. Usually valve computers were designed to stay functional with considerably reduced emission and considerable impedance of the interface layer between cathode metal and coating.
Anyway, I'm surprised cathode poisoning was such an issue. Usually valve computers were designed to stay functional with considerably reduced emission and considerable impedance of the interface layer between cathode metal and coating.
On Beta VCR's...
The stationary upper casting of the drum becomes so highly polished in use (due to tape friction) that it causes the tape to stick to it, particularly on rewind. This can be one of the major causes of poor or no rewind on many machines.
There is a way to restore the original slightly honed finish using nothing more than car valve grinding paste and a cotton pad. It takes all of two minutes to do although you must remove the casting first.
Pinch rollers on some beta machines (thinking of Sony C9 now) have the bearing in the roller offset from the vertical mid point. This was to ensure a slight bias on the tape to make it want to naturally run up the roller and onto the guide flanges. Generic replacements often didn't have the bearing offset and the result could be tape damage in search modes and (apparently) generally poor tape path alignment.
Although heads are extremely fragile in the vertical plane, they are tough when cleaned using a correct horizontal motion and I (and most other techs) used cotton buds soaked in iso. You got to know by feel just what you could and couldn't do when it came to cleaning heads.
Capstans can also become highly polished (same problem as the casting) and refinishing those was also possible.
Tape path alignment should never be altered unless you absolutely know what you are doing. Everything interacts and the basics have to be right first such as ACE head (the audio control head) tilt and any perpendicular adjustments to the capstan motor on machines with that facility.
Cleaning, altering, replacing back tension bands requires the use of a back tension cassette to accurately set them back up again. To much tension and the heads will wear in super quick time.
The actual tape 'stock' seems different on Beta vs VHS, not just coercivity and the like but the physical properties related to the ability of the Beta tape to 'twist' to accommodate the unique tape path run of the Beta machine.
The stationary upper casting of the drum becomes so highly polished in use (due to tape friction) that it causes the tape to stick to it, particularly on rewind. This can be one of the major causes of poor or no rewind on many machines.
There is a way to restore the original slightly honed finish using nothing more than car valve grinding paste and a cotton pad. It takes all of two minutes to do although you must remove the casting first.
Pinch rollers on some beta machines (thinking of Sony C9 now) have the bearing in the roller offset from the vertical mid point. This was to ensure a slight bias on the tape to make it want to naturally run up the roller and onto the guide flanges. Generic replacements often didn't have the bearing offset and the result could be tape damage in search modes and (apparently) generally poor tape path alignment.
Although heads are extremely fragile in the vertical plane, they are tough when cleaned using a correct horizontal motion and I (and most other techs) used cotton buds soaked in iso. You got to know by feel just what you could and couldn't do when it came to cleaning heads.
Capstans can also become highly polished (same problem as the casting) and refinishing those was also possible.
Tape path alignment should never be altered unless you absolutely know what you are doing. Everything interacts and the basics have to be right first such as ACE head (the audio control head) tilt and any perpendicular adjustments to the capstan motor on machines with that facility.
Cleaning, altering, replacing back tension bands requires the use of a back tension cassette to accurately set them back up again. To much tension and the heads will wear in super quick time.
The actual tape 'stock' seems different on Beta vs VHS, not just coercivity and the like but the physical properties related to the ability of the Beta tape to 'twist' to accommodate the unique tape path run of the Beta machine.
It was enough of an issue that an entire generation of special tubes were developed to combat the problem. These became available to the computer makers shortly before the germanium transistor pushed them out of their sockets. There are still quite a few specialized computer versions of the usual twin triodes out there hiding in plain sight with low demand and therefore low prices.
You have a point there.
By the way, the interface layer that can grow between cathode metal and coating when the valve is used at a too low anode current over a long period of time, can also cause a huge increase of 1/f noise. Cathodes with low silicon content, as used in special-quality valves, should be far less prone to this effect than ordinary valves.
By the way, the interface layer that can grow between cathode metal and coating when the valve is used at a too low anode current over a long period of time, can also cause a huge increase of 1/f noise. Cathodes with low silicon content, as used in special-quality valves, should be far less prone to this effect than ordinary valves.
There is a "computer grade" pentagrid converter - pins out like a 6BE6, works like a 6BE6 as best I recall ( been a while since I played with them ), and looks like a 6BE6 except the bottle is about a third again taller with a LOT more getter. Type 7036 IIRC. All of mine are JAN grade GE.
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I remember the 5915A, a hot rodded 6BE6 for computers. It looked just like the 6BE6, so there may be a newer, taller tube tube also. I believe there was a computer version of the 6AU6 too, but I don't remember the number today. I had zillions of computer tubes, but I didn't save the oddballs or those I only had a few of.
The common good ones are the 5963, a computer 12AU7, the 5965 is like a 12AY7 with a bunch more Gm, and the 5964, is a computer 6J6. The 6463 was Philips computer version of the 12BH7. The 7044 and the 7119 were nice tall dual triodes that pin out like a 5687. There are more, but I can't remember the numbers.
I had tons of 5687's but many had obviously seen some severe over dissipation. I threw out the toasted tubes, but haven't got to screening what's left. Apparently the answer to higher processing speed was more current, or someone tried to overclock an old tube PC in true Tubelab style!
The common good ones are the 5963, a computer 12AU7, the 5965 is like a 12AY7 with a bunch more Gm, and the 5964, is a computer 6J6. The 6463 was Philips computer version of the 12BH7. The 7044 and the 7119 were nice tall dual triodes that pin out like a 5687. There are more, but I can't remember the numbers.
I had tons of 5687's but many had obviously seen some severe over dissipation. I threw out the toasted tubes, but haven't got to screening what's left. Apparently the answer to higher processing speed was more current, or someone tried to overclock an old tube PC in true Tubelab style!
Although on a branch line 7199 was a remarkable tube. I have seen many promotional circuits using it which I guess were RCA. UK text book suggest it is a TV pentode+triode with enhanced audio qualities. As far as I can see the pentode did all the work in the Dynaco ST70. The triode is DC coupled to the pentode anode as a concertina phase splitter.
Radford use a similar tube/valve as long tail pair where the pentode is the input device. I suspect it gave a very good pentode+triode hybrid curve. If you like similar to Ultra Linear curves. As a feedback design it might well be a better place to start from. Radford also thought the pentode easy to drive.
EF86 as a pentode microphone amplifier is only slighty more distorted than as a triode. It has greater gain. The likely reason is a very small part of it's pentode curve used. It has a very high output impedance which would suit a JFET op amp very well. The anode load from memory was 470K or higher. I suspect a MPSA94 as constant current source would suit it well. I have some wire ended CV types I must try.
Radford use a similar tube/valve as long tail pair where the pentode is the input device. I suspect it gave a very good pentode+triode hybrid curve. If you like similar to Ultra Linear curves. As a feedback design it might well be a better place to start from. Radford also thought the pentode easy to drive.
EF86 as a pentode microphone amplifier is only slighty more distorted than as a triode. It has greater gain. The likely reason is a very small part of it's pentode curve used. It has a very high output impedance which would suit a JFET op amp very well. The anode load from memory was 470K or higher. I suspect a MPSA94 as constant current source would suit it well. I have some wire ended CV types I must try.
You know what? I'm not convinced that VHS is actually capable of recording fluid motion, aka a full 25/30 fps. The chroma TVL resolution is most certainly higher than VHS.
The picture is also considerably more stable than VHS, Betamax never jumps around unlike VHS. In contrast Betamax just simply adds noise into the picture or the picture disappears/drops out entirely. It never does a half-assed job of "jumping around" and have the tape become misaligned off the head.
The higher chroma resolution is probably attributed to the faster head speed over VHS. I've noticed also that the contrast levels are far higher and deeper with Betamax vs VHS.
There are times when I was convinced that I was watching a DVD this afternoon while I was watching Johnny Guitar + music videos this afternoon, or that i was watching a tape that was recorded in SuperBeta mode. The picture quality is THAT stable, lush in colour and high in contrast.
I'm very surprised that VHS won the format war. Betamax is far better quality all round. VHS is like a kids toy in comparison. I'm convinced that the NTSC standard with its lower resolution has played a part in VHS winning the format war, if all of your content is recorded in NTSC then you aren't going to be appreciative of the higher contrast/Chroma SNR and resolution than you would be if you were recording or watching PAL content.
The picture is also considerably more stable than VHS, Betamax never jumps around unlike VHS. In contrast Betamax just simply adds noise into the picture or the picture disappears/drops out entirely. It never does a half-assed job of "jumping around" and have the tape become misaligned off the head.
The higher chroma resolution is probably attributed to the faster head speed over VHS. I've noticed also that the contrast levels are far higher and deeper with Betamax vs VHS.
There are times when I was convinced that I was watching a DVD this afternoon while I was watching Johnny Guitar + music videos this afternoon, or that i was watching a tape that was recorded in SuperBeta mode. The picture quality is THAT stable, lush in colour and high in contrast.
I'm very surprised that VHS won the format war. Betamax is far better quality all round. VHS is like a kids toy in comparison. I'm convinced that the NTSC standard with its lower resolution has played a part in VHS winning the format war, if all of your content is recorded in NTSC then you aren't going to be appreciative of the higher contrast/Chroma SNR and resolution than you would be if you were recording or watching PAL content.
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If you take Beta and VHS against live camera feed both are very poor. The Beta can go off tune very easilly. I think Sony oversold Beta, then wouldn't issue licences. I would liken it to two cars. One does 105 miles per hour and the other 95, compared to a modern Mercades diesel doing 155 mph it's no big deal. Remember we had live TV to compare so knew of better. Beta did seem more neutral. I was always surprised how OK both Beta and VHS were when seeing how much of the test card was missing. Below is the first thing I saw on VHS. I recorded it the night it came out of the box. I think my boss who I believe was made at the Sony factory told me we would be doing VHS if I liked it or not. I liked it very much. The tapes seemed tougher. It seemed a more honest product.
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Having taken many VHS and Beta apart it was often the VHS that looked to be better thought out. That could be that they sold more and had the money to refine details.
Sony without any justification could be very high handed. They had no ability to make the best of their best ideas. This was sad as many of their older designs were excellent. These often looked a bit hand made inside ( the Boss moaned about that, TV 9-90 being a rats nest, totally reliable ). They were totally reliable and long lasting. About 1980 they lost their way and could have mediocure and excellent produts in the same range where the mediocure would be the upmarket version! When the Nuclear power station went wrong in Japan I thought of Sony.
My favourite Sony designs TC377. TA1010. TA88-ST88. TA5650. TC153. My favourite Beta a Sanyo.
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Having taken many VHS and Beta apart it was often the VHS that looked to be better thought out. That could be that they sold more and had the money to refine details.
Sony without any justification could be very high handed. They had no ability to make the best of their best ideas. This was sad as many of their older designs were excellent. These often looked a bit hand made inside ( the Boss moaned about that, TV 9-90 being a rats nest, totally reliable ). They were totally reliable and long lasting. About 1980 they lost their way and could have mediocure and excellent produts in the same range where the mediocure would be the upmarket version! When the Nuclear power station went wrong in Japan I thought of Sony.
My favourite Sony designs TC377. TA1010. TA88-ST88. TA5650. TC153. My favourite Beta a Sanyo.
Sounds completely plausible. Just like the humble audio cassette evolved into something much better, while retaining the same format. So many millions (billions?) produced, so much money to spend on making it better. Did VHS enjoy the same bonanza?
Also, didn't Betamax have a tape path problem? I remember them jamming up more than VHS.
VHS emerged as the most popular format because JVC was willing to licence the format to other manufacturers, the TV rental companies jumped on this and pre-recorded films (hiring tapes) took off. Sony missed out with a reluctance in the early days to allow other manufacturers to build Beta machines and by the time they did it was to late.
Beta was the superior system in most respects, tape path, video bandwidth and particularly audio (the later HiFi FM modulated audio, not the linear soundtrack).
Visually the chroma performance was pretty good compared to VHS because of Beta's technique of recording a pilot colour burst to give greatly improved synchronisation. Beta also had a larger diameter drum which meant the effective tape/head speed was higher. Lots more reasons why Beta was better
Beta was the superior system in most respects, tape path, video bandwidth and particularly audio (the later HiFi FM modulated audio, not the linear soundtrack).
Visually the chroma performance was pretty good compared to VHS because of Beta's technique of recording a pilot colour burst to give greatly improved synchronisation. Beta also had a larger diameter drum which meant the effective tape/head speed was higher. Lots more reasons why Beta was better
Like with motorcars sometimes the less expensive machines have the more ideal engineering. These days I never see a car that would be ideal to work on at home. My garage admit some aspects of car repairs go over their heads.One example of stupidity was a circa 7 year old Renault Megan that my friend scraped because the heating went wrong. What went wrong was known and cheap. It meant the whole heater matrix and no end of other stuff had to come out. The local garage are very fair people. They could do the job for £400. Then they found a large number of little jobs that had been ignored too long. The mechanic said NO as it far exceeded the value of the car. Asking around other mechanics thought the car was made for quick assembly with no regard to repair. I saw this very often in my work. Yamaha tape decks had complete mechanisms for £40 with heads and flying wires. As a result they seldom needed it. It was a 10 minute job to install. Kenwood had a clutch which should be a simple fix. 3 hours latter the clutch was extracted. It was then very hard to get the frame straight. It was screwed up finger tight then tightened with a tape running. None of that in a book. If I had done another I would have cut some metal away. Why Kenwood hadn't is hard to imagine, Just careless design.
The last generation VHS were like nice watches. Despite being cheap they had thoughtful engineering. I always thought the Sanyo Beta more like the JVC VHS in engineering. Although Sanyo and Sony were linked the machines were different. I used a Sanyo Beta as my first VCR, It was about 30% less than the Sony which I didn't want.
The last generation VHS were like nice watches. Despite being cheap they had thoughtful engineering. I always thought the Sanyo Beta more like the JVC VHS in engineering. Although Sanyo and Sony were linked the machines were different. I used a Sanyo Beta as my first VCR, It was about 30% less than the Sony which I didn't want.
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