Why cant there be a universal cable for every kind of socket?


To elaborate: Why must a USB cable look different from an HDMI cable? Why must we have B-type and C-type chargers? Why use circular audio jacks when it can be “USB’ed” instead? and so on

In: 2

Because the do different things, they have different numbers of wires inside them that carry different kinds of electricity in different directions at different specifications. The hardware each cable plugs into are connected to various hardware and software drivers that are expecting these specific kinds of inputs in order to translate them.

There is a benefit to different type of plugs. You don’t want to plug an audio cable in to a socket that carries voltage. Sending line voltage to a sensitive amplifier or preamp could damage it.

In short, money. An HDMI cable has 5 twisted pairs, 4 solo wires, and 1 drain wire. That’s 15 wires to get the job done. CAT Ethernet cables typically have 8 depending on various things. A USB has 4. And an audio jack (without mic) has only 3. Why would you pay for a more expensive cable than you need? So the next question is, could we standardize the plug and have a bunch of different options for how many wires run between them. People have tried that. Back 15-20 years ago, serial ports (actually called DF-9) we’re king. 9 pins, but as few as 3 might actually be used depending on the application. It was fairly widely used, but there are some other issues that toppled it. It was a lot bulkier than modern plugs, and connectors are still a big portion of the cost of a cable, especially shorter cables. Also, more pessimistically, if you make your connectors unique or just choose rare or weird existing ones *cough *Apple* then people will be forced to come to you for the accessories too. More money

Lastly, different plugs and wire configurations are good at different things. Remember above when I said 5 twisted pairs? Twisted pairs are commonly used for noise rejection. Most applicable when running digital data through a cable. Analog data can be more resilient to noise, mostly because if 1μs of a song comes out kinda funky, who cares? But signal quality is still very important. Reflections and distortions can happen at connectors especially because the impedance can change drastically compared to the wire it was just running through. So your typical 8mm or 16mm aux jacks are specifically designed for audio signals (20-20,000 HZ). Higher frequencies are often used to carry additional data like in cable internet. Coax cables with BNC connectors do a better job of reducing reflections in up to several MHz transmissions. In fact, BNC connectors are often sold by resistance in Ohms. You need to know what the impedance of your source and load look like, then use the right resistance connector to match them as close as possible to avoid reflections.

USB-C is an attempt to do all these things, but it’s fairly new, and there are plenty of older standards still out there. USB-A (the “normal” USB) has been out over twenty years, as has HDMI. Back then, USB was slow & was designed to be cheap, so cable tolerances were not very high. As a result, USB’s signaling technology wasn’t fast enough to transmit digital video. So HDMI was created with cables with different tolerances for video.

USB *did* manage to replace a lot of older standards — parallel printer ports, serial modem ports, keyboard & mouse ports, RS232 joystick ports… but until USB v3 it didn’t have the bandwidth to transmit video. At that point, we had lots of different USB connectors: USB-A, USB-B (the “printer” connector), mini USB (common on digital cameras), micro USB (most cell phones until ~2017), lightning (Apple)… So the USB consortium looked at what was needed now, and came up with USB-C.

USB-C (and Thunderbolt 4, which is a superset of USB-C) could conceivably become almost universal & be used for pretty much all digital consumer signals. Even then, though, there’s variation there, as Thunderbolt 3 & 4 cables are two seemingly-identical-but-different-electrically cables. We’re not out of the woods yet.

Meanwhile the various audio jacks (small and big headphone plugs, RCA, 1/4″ “guitar” cables, etc) are far older, and they carry a different *kind* of signal: analog audio. These are each well established for a certain use, and the fact that they’re different could actually be seen as an advantage, as they keep you from hooking up electrically-incompatible signals (like plugging your headphones into the phono output of your record player).

“Universal” cables end up being mediocre at everything

The best cable option for short ranges would be DisplayPort as it does power transfer and has crazy bandwidth so now all your devices need to support a mini-DP connector

Your headphones are now much larger to support the mini-DP plug.

Your keyboard is now much more expensive because DP signaling is more hardware intensive

Your motherboard is now much more expensive because every port needs full bidirectional DP support just in case

Nothing is compact, nothing is cheap, and everything is supporting more features than it needs.

We have different cables and sockets for different applications because they’re better at those applications. USB is cheap, moderate length, and fairly fast. HDMI and DisplayPort are expensive, ludicrously fast, and only used in applications that require it. Ethernet requires special hardware but is fast and can cover insane distances compared to the rest.

One design to rule them all drags everything down with it

18 competing standards each excel at their specific job

What those guys said, plus legacy reasons.The days of analog technology lasted for 70-80 years.Digital signals can have VERY different physical & electrical requirements than analogue signals.And the invention of transistors made power requirements change.And microprocessors became more efficient, changing voltage requirements.And the invention of solid-state power supplies changed requirements again.plus different nations has settled early on on incompatible power deliveries to the home.

And some early designers made really, REALLY dumb mistakes, such as the designer who made the USB 1 connector, who made it fit in just 1 rotational orientation. He didn’t HAVE to do that.

And corporate greed alters some designs for the worse: cell phone companies early on used proprietary wall wart plugs to force you to buy their chargers ONLY. The EU’s rules demanding common charging ports put an end to most of that nonsense.

And then the entrenched interest in maintaining the investment in existing infrastructure once you’ve already bought it generally means old connector formats tend not to die out. Plus electronics tend to last a LONG time. There’s a reason you can still find LP record players in thrift stores.

The #1 reason is that electronics are sensitive. If you plug something with amperage into something not designed to take that kind of current, you are going to have a _very_ bad time. Different plugs prevent this from happening.

Beyond that, different plugs help differentiate what information can travel. A headphone jack outputs analog audio, while an HDMI jack outputs digital video _and_ audio. Your headphones can’t do anything with HDMI signal, so people will get confused when they plug in their headphones to the wrong jack and nothing happens.

There _are_ universal standards, like USB-C, that are attempting to create a universal cable that can do everything, but that tech is more expensive than a “dumb” cable and jack that only does one thing. A Thunderbolt-4 USB-C cable could run you hundreds of dollars, while a cheap analog audio cable will be under $5 – why spend so much more when you don’t have to.

HDMI cables don’t have power requirements. They simply carry a signal. It’s a pretty large plug compared to the rest. It’s capable of transmitting and receiving a signal. Both end devices are powered by other means, due to power requirements. Adding power wires not only make the cable bigger, but can cause issues with picture and sound quality.

USB cables also carry a signal, are capable of transmitting and receiving a signal, and provide a regulated voltage. USB B provides 5 volts, USB C has variable voltage available 5, 9, &, 12 volts & can transfer data faster. They are powered from the computer, a wall wort, or some other USB power supply. They’re used for programming low voltage, low amperage devices, to program the device, and for data transfer from devices that may not see power otherwise.

Headphone jacks and plugs are available in a 3.5mm & 1/4” sizes, depending on how much power you’re trying to send them. The 3.5mm is most common because it’s compact. Both are available in 1 or 2 ring varieties, allowing mono or stereo sound while sharing a ground. The 3.5mm is available in a 3 ring, to allow video as well. The 1/4” plug is great if you’re running an amp to some nice headphones. Headphones are often used when mobile and the deep plug helps prevent accidental disconnects and it’s pretty durable compared to the rest. The 1/4” plug is pretty common with amplified instruments because the size adds to its durability.

Mostly because we need one power outlet to do many, many different things. If we did t have different kinds of chargers you would have to have several different kinds of outlets in your house.

USB C will replace these things in the long term. It just takes time

There’s been a few monitors that use USB C (e.g. LG UltraFine). But otherwise you can get a USB C to HDMI cable

You can do audio over USB C too – but manufacturers seem to have gone the fully wireless route

As for the power issue people mention, I’m pretty sure it’s wrong. USB C negotiates power delivery between devices, so if there’s no agreement to provide power, there wont be any power provided

As an analogy, we don’t have a universal type of car. Instead we have sedans, sports cars, mini-vans, pickup trucks, school buses, ambulance etc., each having its own purpose.

Cables are no different:

* Some cables are designed to cover longer distances, while others are meant for very short distances. E.g., ethernet can span 100 meters, HDMI maxes out around 20 meters. while the thin USB cable is designed for less than 3 meters. A USB cable that can go 100 meters would probably need to be as thick as an ethernet cable, which wouldn’t be convenient for mobile devices.
* Some cables are meant for industrial use instead of home use. E.g., professional microphone cables have very thick XLR plugs (about 10x the thickness of a USB C connector) because it has to be very robust physically and electrically for use on a live stage, etc. It would be disastrous to use USB C for a live stage production, and it would be inappropriate to use XLR plugs on a slim smartphone.
* Cables like HDMI must deliver high bandwidth (48 Gbps) to support 8K video, etc., while for USB C 20 Gbps is currently sufficient.
* USB C is meant to be used for smaller devices so it’s useful for it to carry < 100W of power. But 100W is way too small many TVs, home theatre systems, etc.. These appliances are typically plugged into the electric mains anyway, so a HDMI doesn’t need to be designed to carry power.

TL;DR: we can’t have one universal cable because we want to have the best cable thats suited for its intended use. We need thicker cables for long transmissions; We want robust connectors for tough environments; We want high bandwidth cables for our home entertainment; We want thin power-carrying cables for our mobile devices.

For USBs they are “keyed” to make sure power goes in one direction, on top of everything else smarter people say.