Electronics Wonder

Two questions about electronics: My son has a converter box to convert from cables with male RCA connector to an HDMI cable. He is trying to connect a game controller (with the HDMI female connector) to an older CRT-type TV with RCA jacks coming off the back.

Two things about all this:
A) The RCA is on the input side and the HDMI is on the output side of the box. But, why should it matter*? When I ask this, I mean (a) is there a diode or such controlling the flow of data? And, (b) why is the converter box AND flow of the data stream needed at all when…

B) We found we can purchase a cable with male RCA connectors at one end and HDMI at the other. No converter box and no directional issues. How’s that all possible (when we saw above a converter was needed, for one)?

*But, since it does matter, this converter box’s input / output physical configuration is the reverse of what he needs.

because the box is a transcoder, it is designed solely to take in analog video/audio and convert it to a digital HDMI output. complex digital logic like that can’t simply be “run in reverse” unless it’s specifically designed to.

because that cable is meant to be used with a console or computer which can alter what kind of video signal it outputs if it detects that cable is connected. all of the “hard work” of producing an analog or HDMI stream is done on the device, the cable is just that, a dumb cable. if the game console isn’t able to sense that cable and switch its output then that cable will be useless.

It’s all about converting digital signals to analog signals and the other way around.

Converting a digital signal like HDMI to analog is very easy. That’s why the transcoder chip that does it is so small that they can easily hide it in cable B. This cable will only ever carry a signal from an HDMI output to an RCA input.

Converting an analog signal like RCA to a digital signal like HDMI is very hard because you need high sampling rates and such to make a high quality replication of the analog signal in digital form. That’s why cable A probably cost 10-100x more than cable B. It can only ever carry a signal from an RCA output to an HDMI input.

The conversion from digital-to-analog is one way per transcoder, so you need to be careful about what direction of cable you buy. That’s why only one of the cables worked.

Why on Earth would you want to play something with an HDMI output on a fuzzy CRT TV?

You could probably pick up a flat screen TV from a charity shop for less than the cost of a converter.