orange808 wrote:
What's going on with the NTSC/PAL switch on those?
Since NTSC and PAL have different subcarrier frequencies for color, among other differences, the chip has to know which frequency to modulate on. Every rgb to composite + s video chip out there solves this by having a pin that takes +5V supply voltage for NTSC and 0V (ground) for PAL. Very easy to set with a toggle switch. Mismatching NTSC or PAL to the TV gives classic black & white image because TV can't find color information where it expects. RGB doesn't have different NTSC and PAL encoding, just 50 or 60 Hz.
mrsmiley381 wrote:
Josh128 wrote:
Its why I asked. I have yet to see a good test of different converters on the net showing differences. I'd like to give Mike Chi's box a try but Im really not confident I'll see any difference on my 36" Wega vs the cheap modded clone Im running now.
Isn't there also a question of whether or not the transcoders take the analog signal, convert it to digital, perform the transcoding, and then convert back to analog? I recall reading somewhere that the Koryuu does this when transcoding composite to component and that it could cause problems with optimized sample rates with upscalers. Curious to know which of these solutions go the analog-digital-analog route, including that Time Harvest one.
Is a very good question about transcoders converting to then from digital versus keeping in analog. Would absolutely degrade video quality. I found two analog solutions with a little searching:
Chip-free NTSC DIY rgb to component design Mike Chi found on page 8 of a 1994 technical journal that he then verified under oscilloscope:
https://shmups.system11.org/viewtopic.php?f=6&t=63338Expects csync injected on the Y output. Not the design used in RGB2COMP, judging from picture but you could wire on a breadboard for $10, not including connectors. Page 9 shows another op amp circuit setup and reversing to go component to rgb. Smart I guess of Analog to publish the document since it uses their op amps.
Another NTSC DIY (sorry PAL) solution using BA7230 chip that would also cost around $10:
https://easyeda.com/dekkit/rgb-to-component-transcoderChip datasheet is not as descriptive as I'd like but I don't think it's converting back and forth with digital for analog input.
Way to tell is which region a circuit or chip is if it doesn't say, is looking for 3.579545 (3.58) MHz for NTSC, whereas 4.433618 (4.43) MHz is PAL color frequency.