If you are currently looking for a new audio interface, you are probably wondering about the connectivity: should you get a USB 2 or USB 3 interface?
The fact is that today, while USB 3 is quite common for external hard drives, this is not the case for sound cards: most are still USB 2.0, or Thunderbolt (with a few models still using Firewire, which is on the verge of extinction).
Even the new models coming to market are USB 2.0!
But why is that?
Why don’t manufacturers use USB 3?
If you buy a USB 2.0 interface today, will it be obsolete in two years?
Wouldn’t latency be better with a USB 3 interface? Or overall performance?
All the answers to these questions are in this article! 🙂
USB 1, USB 2, USB 3… a bit of history
USB, or Universal Serial Bus, has been around since 1996.
Beyond the connectivity that everyone knows, it is primarily a standard that allows different computer peripherals to communicate.
Typically, a computer and an external hard drive… or in our case, a computer and a studio audio interface.
Without getting too technical, you can keep in mind that several types of messages can be exchanged via USB between devices: in our case, audio data is transmitted via what are called isochronous transfers, while information related to, for example, the sampling rate is transmitted via interrupt transfers.
As the years went by, different versions of the USB standard appeared, primarily resulting in ever-increasing data rates:
| Version | Year | Data Rate |
|---|---|---|
| 1.0 | 1996 | 1.5 Mbits/s |
| 1.1 | 1998 | 12 Mbits/s |
| 2.0 | 2000 | 480 Mbits/s |
| 3.0 (= 3.1 Gen 1) | 2008 | 5 Gbits/s |
| 3.1 Gen 2 | 2013 | 10 Gbits/s |
| 3.2 | 2015 | 20 Gbits/s |
In other words, USB 3 offers a data rate at least 10 times higher than USB 2.0.
Should we conclude that a USB 3 interface will be faster than another model still using USB 2.0?
The answer is not so simple…
Do we need USB 3 on audio interfaces?
If manufacturers tend to stick with USB 2.0 interfaces, it is not to minimize costs or because they have not yet followed the trend.
Compatibility between systems
The first reason is that, as of now, not all systems have USB 3 ports yet.
In fact, if you buy a motherboard today, even a high-end one, it is highly likely that it offers both USB 3 and USB 2 ports.
In theory, USB 2 and USB 3 are compatible: you can plug a USB 2 device into a USB 3 port, and vice versa.
In practice, however, there are sometimes some small issues (often resolved via a driver update, though).
Also, manufacturers likely make the choice for compatibility by offering USB 2.0 interfaces.
But USB 3 is faster than USB 2, right?
But USB 3 is faster than USB 2, right?
So if my interface is USB 3, it will work better than USB 2.0 and latency will be lower!
And there will be fewer crackles and pops and latency issues!
Well, contrary to what one might think, a USB 3 interface will not be faster and will not offer better performance.
Indeed, the increase in throughput that the USB 3 standard brings compared to the USB 2.0 standard primarily corresponds to an increase in the available bandwidth.
A sort of maximum amount of data that can be transmitted per second.
To illustrate the concept, imagine a tunnel with a single lane, and a speed limit of 80 km/h. If you add similar tunnels next to it, you will certainly be able to pass more cars, but they will not be able to go faster.
It’s the same for USB.
If we look at the following graph, we see that the bandwidth used to transmit a signal of 40 stereo tracks (24 bits @ 96000 Hz) is strictly identical in USB 2.0 or USB 3:
In other words, USB 3 allows for more data to be transmitted, but not to send it faster — at least as long as you do not exceed the maximum throughput.
However, for audio data, since you can transmit about forty tracks in real-time without any problem… this means that for home studios and even a large number of professional studios, USB 2.0 is more than sufficient.
To convince ourselves of this, let’s do the calculation:
If we take our 40 stereo tracks, that means we have 80 individual tracks (1 stereo track = 2 mono tracks) each sending a sample 96,000 times per second, corresponding to a data block of 24 bits.
So:
Bandwidth Used = 80 x 96,000 x 24 = 184,320,000 bits/s = 184 megabits per second
If you remember the table at the beginning of the article, with the USB 2.0 standard, we have 480 megabits per second… so 2.5 times more than necessary to transmit the signal of the 40 tracks.
USB 3 therefore brings no improvement, which is why manufacturers choose to stick with USB 2.
In practice, the audio signal is not the only signal transmitted via the USB bus. If you really want to get into the details, check out this article on the use of the USB standard in the audio field.
What about USB-C?
Some audio interfaces, like the latest generation Focusrite 2i2, feature a USB-C connection.
This has become quite popular in recent years, more or less at the same time as USB 3.1, and the two technologies are often confused.
However, they are not the same thing at all:
- USB 3 corresponds to the communication standard between two devices,
- while USB-C is a type of connector.
In other words, via a USB Type-C connection, it is possible to transmit a signal using either the USB 2.0 standard, the USB 3 standard, or even the Thunderbolt standard!
In conclusion
Ultimately, you will have understood: USB 3 does not really provide any added value compared to USB 2.0 when it comes to audio management, unless you need to record an extremely large number of channels at the same time.
If you buy a USB 2.0 interface today, it is therefore unlikely to become obsolete next year!
► Continue reading by checking out my recommendations for studio interfaces…