1

The USB-C dream is to have a single cable that provides connectivity to my external displays, ethernet, USB hub, etc.

All of the components will be stored in a drawer or mounted out of view. A single, long USB-C and/or Thunderbolt 3 cable will connect the hidden messy components to the laptop on the clean visible workspace, as if you were in an Apple Store.

Unfortunately, nearly all of the USB-C and Thunderbolt 3 accessories, dongles, hubs, and docks that I want to use feature a 6-inch or shorter "pigtail" cable for connectivity to the laptop:

Monoprice Thunderbolt 3 Dual DisplayPort Mini Dock

If I use such a device, it forces all of the DisplayPort, HDMI, ethernet, and USB hub cables to be located inches from my laptop. They cannot be hidden behind the display or mounted to the back of the desk.

What options exist for converting such a short pigtail cable to instead use a longer, nicer Apple cable?

  • USB-C Coupler?
  • USB-C Extension Cable?
  • Some kind of USB-C hub?
  • Converting the pigtail cable to a receptacle?
  • Somehow opening or splicing the dock cable?

Any solution should of course pass through all of the connected ports and accessories. It should also work... which the reviews of many products state they do not.

Is there anything in the USB-C or Thunderbolt 3 spec that prevents these types of solutions from being used?

2

Thunderbolt 3's full 32/40 Gbps mode really pushes the cable's high-speed wire pairs to their maximum throughput limit, such that the signals only reach about 0.5m over a passive cable before the signals degrade to undecodable mush, and only reach 2m with a much more expensive active cable that has special repeater chips built into the connector housings at both ends of the cable.

10Gbps USB SuperSpeed+ (a.k.a. 3.1 Gen 2 or whatever they just renamed it) only reaches 1m over a passive cable, and has no provision for an active cable.

This is why extender cables are nonstandard/out-of-spec. There's just no surplus signal integrity to allow extender cables to work.

1

Assuming you already have a multi-purpose hub like pictured in the original question, you can use a USB 3.1 C to C extension cable. Sometime's they're called gender changer cables. Not all will carry Thunderbolt signals, not all will carry 3.1 Gen 2, and many will be mis-advertised. Here are some examples : https://www.amazon.com/s?k=usb+c+extension+cable&i=computers&ref=nb_sb_noss_2

If you haven't already bought the hub, it's worth while getting one that's powered, plus having all of the ports.

I don't suggest trying to splice the cable.

  • Have you tried one of these extensions? – pkamb May 21 at 16:47
  • Only with very short distances. Thunderbolt requires power for any significant distance, and the cables are not universally labeled. Given that OP is already considering splicing, and is already spending money on the dock, a USB extension cable is a cheap and worthwhile test. Your comment encouraged me to look up other models of USB dock, which I'll put in another answer. – Christopher Hostage May 21 at 17:17
  • I think I'd prefer a coupler rather than an extension cable, but those seem to be even rarer. – pkamb May 21 at 17:43
0

If you're willing to hide a powered USB dock behind a monitor, and just lead a USB C cable from it to the place you put your laptop, then you have multiple options. Power delivery is the limiter for the short pigtails that OP was originally looking at. There are some USB C docks that have longer USB C source cables, but they're not always advertised, and they're not guaranteed to work across different brands and devices. Dell dock WD15, Lenovo ThinkPad USB-C UltraDock, and many others.

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