Quote:
Originally Posted by Alex KL-1
Thanks for the info.
Wondering about it, perhaps is asking too much for having a solid DC restoration in sets not having stabilized +B (not counting the HV reg. here) and/or DC stabilized gain stages, so perhaps is a compromise between price and performance at all.
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Lower DC restoration makes the set less susceptible to mistakes in black level in the signal, but I always thought that was a poor excuse because the resulting errors in the receiver due to DC changes with picture content were just as bad.
Nevertheless, you have to note that NTSC had terrible problems maintaining proper black level at the broadcaster or analog cable head end, due to the unfortunate inclusion of a 7.5 IRE unit black level in the standard instead of setting black at blanking level. There is no reference in the signal for 7.5 IRE, while zero IRE (blanking back porch) is always there. This was originally in the black and white standard to provide some room to prevent clipping blacks in the cruder video processing circuits, but even better tube gear that didn't clip blacks would drift. In hindsight, the NTSC standard for black level (7.5 IRE +/- 2.5 IRE) should have been changed to zero IRE when color came along. I seem to recall that Japan did this in their broadcasts.