Mini-guide to USB cables
You’ve got a shiny SuperSync15. You plug in your cable and it works but you’re getting half the speed. Or maybe you have a ThunderSync hub, you pop your cable in and nothing happens at all… what did you do wrong? In this mini-guide to USB cables, we’ll show you what to look for from both cables and ports, where to check for more information on Cambrionix Connect and what kinds of messages you might see on your host computer.
The differences between USB cables & ports
The first thing to know is that USB2, USB3 and USB4 all refer to the type of USB spec your cable uses. Since each generation within these types has widely different speeds, most manufacturers just list the speed directly in the product information for their cables now. Use that when choosing what to buy instead of a specific generation of USB (USB 3.0 versus USB 3.2). If a manufacturer is unwilling to tell you the speeds, it’s probably best to avoid purchasing that cable.
The designation USB-C (circular) and USB-A (rectangular) are the shape of your cable connector itself. Make sure you have the right one for the right port. And lastly, Thunderbolt is a standard made in collaboration with Apple to offer display output support, higher transfer speeds and cross-compatibility with standard USB ports. All Thunderbolt ports are also Type-C ports, but not all Type-C ports are Thunderbolt ports so you need to look for the lightning bolt or check your host device’s specs.
Signs of USB cable quality
We don’t recommend cables without one of the USB IF certification marks shown below as they are not independently certified and guaranteed to work.
You should also know that a thicker cable diameter often means that your cable is likely to be USB 3.0 compliant and therefore able to maximise power delivery to your devices. So, if you’ve got a junk drawer of cables to choose from, thicker is likely better. Anything else like braided cables, cable reinforcements, cases and similar features are just there to increase the durability of the cable itself. They won’t do anything to impact speeds.
How long should a USB cable be?
The length of a USB cable is not just a matter of convenience, it also directly impacts the cable’s performance. USB-IF (USB Implementers Forum), the organisation responsible for defining and maintaining USB standards, has established guidelines to ensure optimal functionality and signal integrity. However, these recommendations vary depending on the USB generation in question.
Early USB generations – defined lengths
For early USB standards, the USB-IF set specific maximum lengths to ensure reliable performance:
USB 1.0: Maximum length of 3 meters (approximately 10 feet)
USB 2.0: Maximum length of 5 meters (approximately 16 feet)
These lengths were chosen to minimise issues like signal loss and latency over longer distances.
USB 3 and beyond – performance standards
With the introduction of USB 3.0 (now also referred to as USB 3.2 Gen 1) and later generations, the USB-IF shifted its approach. Instead of specifying maximum cable lengths, the organisation emphasised performance criteria such as:
Signal propagation delay – how long it takes for a signal to travel down the cable
Attenuation – the loss of signal strength over distance
As a result, the practical maximum length of a USB cable is now determined by its ability to meet these performance requirements. Here’s a breakdown of the typical lengths for modern USB standards:
- USB 3.2 Gen 1 (USB 3.0, USB 3.1 Gen 1): Up to 2 meters (approximately 6 feet)
- USB 3.2 Gen 2 (USB 3.1 Gen 2): Up to 1 meter (approximately 3 feet)
- USB 3.2 Gen 2×2: Up to 1 meter (approximately 3 feet)
- USB4: Limited to a maximum of 0.8 meters (approximately 2.6 feet)
Why shorter USB cables for newer standards?
The shorter lengths for newer USB standards reflect their higher data transfer rates and stricter performance requirements. For example:
USB 2.0: Supports up to 480 Mbps, which allows for a longer cable without significant signal degradation.
USB 3.2 Gen 2 and USB4: Operate at much higher speeds (up to 40 Gbps for USB4), making signal loss and interference over longer distances a critical concern.
To overcome these limitations, users can opt for active USB cables or USB hubs with signal repeaters for extended distances. These devices amplify the signal, enabling connections over longer lengths without compromising performance.
Ensuring compatibility and performance in USB cables
To ensure a USB cable works reliably, choose a USB-IF-certified cable, as it guarantees compliance with performance and quality standards. Certified cables are tested for compatibility, offering peace of mind, while uncertified options can lead to inconsistent performance or failure. Matching the cable to the appropriate USB generation is also crucial for optimal functionality.
Signs your USB cable is failing
If you experience disconnections or get any warnings that a port is overloading, a device isn’t recognised, one of your USB accessories is disabled or there has been a USB device malfunction; then the cable may be damaged. Also, please don’t use cables that show visible signs of wear or damage like cracks, tears or singe marks. If you’ve not had your cable for a long time, there still might be a warranty on it, so check with your cable manufacturer.
What you’ll see in Cambrionix Connect
When you view a device in Cambrionix Connect, it will tell you if you’re using a USB 2 or 3 cable and if you could be getting higher speeds:
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