This ability is acquirable through practice, from installing computers and televisions many times. With little working room available, being able to connect the cables after a glimpse of the connectors' positions is very useful.
But at the same time, this practice can be dangerous.
So I was connecting my speakers to one of my amplifiers. I saw the black connector of the cable was already in. So I took the red one, inserted it, then turned on the amp.
Well not totally nothing, the other speaker is working fine.
Reinserted the connectors on the amp side. Still nothing.
Looked at the connectors on the speaker side in order to reinsert them.
Both the red and black connectors plugged into the black terminals.
It can happen because my speakers are bi-wireable (or bi-ampable for people who don't acknowledge the legitimacy of that concept), and the terminals are arranged in a neat row:
I wasn't worried, because the short-circuit protection of this amplifier is tried and tested (not the first time I accidentally shorted it, which was 50% due to my own fault).
But try that on another amp, and who knows. I wouldn't try that on circuits designed by d.i.y.ers, for example.
This happened because I did not look at things when I am touching them. I did look at the black connector, but s*** happens, and at least if I had looked, I would have noticed the mistake before powering up.
While the "eyes-free" method is (relatively?) safe with computers and AV equipment, this is because of the unspoken rule of not using the same connector for two different things. As in two different types of signaling, voltage and etc. (Different USB devices use the same USB connection, and different-colored analogue RCAs, that's fine.) Or at the very least, if the same connector has to be used, make it in such a way that things don't explode when you plug them into the wrong hole.
Because, even if they are looking, people will plug any thing into any hole that fits. And push any switch that they can. I wonder what that 230V switch does.
This is one of the reasons why the USB connector is square on the equipment side (because connecting two computers via a normal USB cable will cause things to fry), the LPT cable is different on the computer vs the printer, why the 15-pin midi port is different from 15-pin VGA D-sub, why some connectors must be male and why some female. Apart from the obvious money from licensing. Well yea.
Well, audio is a place where such rules of safety (there are others too) cannot be properly followed, due to too many different requirements, the need for compatibility and the lack of customized standards.
However, many places are still using bare wires. Carries anything from turntable output to 230V live AC. Ok, maybe live AC is exaggerating, but speaker cables capable of a few amps is possible.
And those exposed connectors, omg. I don't care if it is isolated (from the mains) or not, 100V is still 100V and it still burns you and stuff.
It would take some effort to child-proof this thing. But then again, the way people place their equipment on stands and platforms, they are probably not intending to have babies.
Anyway, my point is that getting high-current wires with opposite polarities to share the same type of connectors which are placed next to each other is a very bad idea, even if the connectors are color-coded.
Credits: All pictures are from the internet.
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