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  1. Member StuR's Avatar
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    Sync
    Hi, Im trying to understand some of the pro TBC terminology. Many at a certain level start to have an option to adjust 'Horizontal and Vertical Phase'. Does this simply move the whole picture up/down, left/right?
    The unit I have with a TBC allows additional sync lock settings 0/1/2/3. Setting 2 holds poor VHS but only works when set whilst playing tape. If you stop the tape and start again the picture is half top and half bottom with a black line between. Switching setting off/on easily corrects but from this it seems to suggest that the vertical framing has been halved.
    The manual doesn't go into detail about what is being done. Can someone explain please.

    The reason for asking is I'm trying to translate terms to compare TBC's. I'd like to know how that sync lock adjustment is usually termed and what kind of functions are important to look for.
    Quite a few ext. TBC's don't seem to have much in the way of options for locking on to sync, can I take it they just do or are they likely to be depending on an additional ext. source?

    S/N ratio.
    They usually quote a rate of high 40db's, but apparently 60db is preferred. I've noticed Signvideo quote high S/N ratios but they don't seem to have UK models (or cheap second hand ones).
    Can't find S/N for my TBC but I imagine it's not that great.
    How important is this figure and does it become more important on older VHS e.g were the input signal would be weaker.

    Cheers
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  2. Member
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    Hotronic AP41 is a good unit. I have one. There are 4 listed on ebay. If you wait and watch you can get one cheap. It is a real TBC.
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  3. Member StuR's Avatar
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    Hotronic AP41
    yep looks good with lots of functions, unfortunatly it's a US model, I'm looking for UK PAL models only. Some of the multi-standard converters are made for US, UK .. market as they run on 90V-250V, they also often have TBC/sync/proc amp. They are possibly worth the costly shipping, a problem easied by the exchange rate .
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  4. Preservationist davideck's Avatar
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    Many professional TBCs include a "GenLock" input to synchronize the TBC output timing to an external "House Reference". The Phase control(s) may be associated with this function to provide an adjustable timing offset between the GenLock input and the TBC output.

    Some TBCs also provide Centering/Blanking adjustments of the image within the raster.

    The Sync Lock Setting selection in your TBC is rather unique. You should not assume that all TBCs have this same flexibility. Ironically, some professional TBCs expect professional quality tape sources and are actually less tolerant of signal disturbances than lower cost TBCs designed for consumer VCR sources.

    The TBC S/N Ratios are primarily a function of 8 bit versus 10 bit processing. The low S/N Ratios of consumer analog tape formats typically dwarf any S/N issues introduced by the TBC. Digitizing VHS to 8 bits usually results in only 7 or 6 significant bits with 1 or 2 LSBs of noise. 10 bit processing just adds two more LSBs of noise.
    Life is better when you focus on the signals instead of the noise.
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  5. Member StuR's Avatar
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    davideck cheers for reply I thought you'd vanished from this forum! You've sort of helped abit but every answer results in 2 or 3 questions, I may need to go away and think for a bit!
    The sync lock option is clearly a function designed for the non-pro market. I understand that some tbc's require an ext. source to supply the sync. so I presume they have no option to generate their own clean signal. The more basic tbc's must all create their own. I still don't understand whats happening but I only want to know to be able to compare with other models, after that if it works - it works!
    s/n ratio I was just presuming this would give so indication of the quality of the image as it passes through the tbc, ie not adding digital noise or degrading colour. I've done a lot of test with my tbc/visionmixer and it's only a minor loss in quality, I'm sure many are worse, but without actually testing another unit it's had to judge. That means buying the damn thing first though!
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  6. Preservationist davideck's Avatar
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    Originally Posted by StuR
    I understand that some tbc's require an ext. source to supply the sync. so I presume they have no option to generate their own clean signal. The more basic tbc's must all create their own. I still don't understand whats happening but I only want to know to be able to compare with other models, after that if it works - it works!
    The TBCs with GenLock inputs typically do generate their own "clean" reference; if no GenLock input signal is connected, then their output timing will simply free run just like the more basic units. But if a GenLock signal is connected, then the TBC will synchronize and align its output to this reference. This capability is necessary in a studio environment where multiple sources fed to a video switcher must all be synchronized and aligned with respect to each other. For capturing a single source, however, the GenLock capability serves no purpose.

    This post from long ago provides additional info;
    https://forum.videohelp.com/topic279530.html#1373230
    Life is better when you focus on the signals instead of the noise.
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  7. Member StuR's Avatar
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    I have that saved and have read many a time, unfortunatly you clearly understand this a great deal more than I do and I don't know if I'm the only one but it's a bit of a struggle I've found a fair bit of info on introductions to TBC but beyond that it gets very hard to find anything in laymens terms.

    I've PMed you Davideck to have a look at a model I'm intersted in.
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