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Why USB-C audio is a stupid idea

1.9.2020

Translation: machine translated

It makes sense to use the USB-C connection for audio. The 3.5 mm connection has its origins in 1878, when telephone operators used it to make connections on a large tableau. But perhaps there is a reason why analogue technology has survived for almost 150 years ...

The year is 2020 and USB-C is the present. The connector is symmetrical and can be plugged in on both sides. Thanks to the USB 3.1 protocol, data transfers of up to 10 gigabits per second are possible. Smartphones, laptops and other devices can be conveniently supplied with power via USB-C. The connection also replaces the outdated 3.5 mm jack connections and promises to become the new standard for audio. Although audio transmission is one of those things ...

Entertainment for the whole bus

The other day I packed the wrong headphones. They are indeed USB-C headphones, but the ones that came with my old Samsung smartphone. They are not compatible with the new OnePlus Nord, which I only realise when I turn up the volume on my mobile on the bus and still can't hear anything. Logically, the in-ear headphones block the ear canal, but they don't work. Roman Mars from "99% Invisible" tells the other passengers about why Japanese people are so fond of mascots over the mobile phone speakers turned up all the way. By the time I realise this, I've got the evil eye of the morning passengers on me. I can't blame them. I put the mobile phone in my pocket with a bright red head and wonder what exactly went wrong. USB-C has gone wrong.

When a person has a bad experience, they remember it and forget all the good experiences. This is called "negativity bias". In my case, for all the benefits that USB-C offers, I will always remember the episode from the bus.

USB-C, ojemine

To save myself any more embarrassing moments, I test the two headphones on my two smartphones. My suspicion: Each manufacturer does its own thing and therefore the headphones are not compatible. But it's not that blatant. The OnePlus headphones work perfectly with the Samsung. But not the other way round. The picture is different on a laptop with a USB-C port. The Samsung headphones work here, but the microphone does not. The OnePlus plugs do not cause any problems, the microphone also works here. I notice that Windows recognises the headphones as a "plug and play" device. My assumption that every manufacturer brews its own soup could be confirmed.

The new theory: The USB-C headphones receive a digital signal in zeros and ones from the mobile or laptop and then convert this into an analogue waveform using a digital-to-analogue converter. After all, audio playback requires an analogue signal, otherwise no sound waves can be produced. With the 3.5 mm jack, this conversion already takes place in the smartphone or laptop. The jack plug therefore only ever has to conduct a voltage in wave form. However, when mobile phones and laptops send digital signals, things get more complicated. The headphones receive zeros and ones, but the headphones need to know how these are converted into an analogue waveform. It's like with languages: If you don't understand Chinese and the other person doesn't understand German, you'll never be able to communicate with each other. The Samsung plugs probably don't speak the same language as my OnePlus mobile, so they don't work, at least that's my theory.

Analogue signals can be any number between 0 and 1.nalogue signals can have any value between 0 and 1, digital signals are either 0 or 1

This is probably the crux of the matter. During my research, I came across an article from Soundguys.com that explains this well. The reason is the USB standard, which is constantly evolving. Digital audio signals have been able to be transmitted via USB since the end of the 1990s. At that time, the "USB Audio Class" specification was introduced in version 1. Today we are at version 3, with more speed, less energy consumption and new features. For everything to work properly, both hardware and software must understand version 3. If a headphone can handle version 3, this does not mean that it will work with a device that can only handle version 2 or 1 of the "USB Audio Class". They may speak the same language, but at different levels. If you understand a little Chinese, you are still far from being able to take part in an in-depth conversation with a Chinese person. USB-C is therefore unsuitable as a replacement for the analogue jack in terms of compatibility. There is no indication of which format a headphone or end device can handle. You almost always buy a pig in a poke or go to your grave researching whether the headphones you want will actually fit your device.

As if that wasn't complicated enough, USB-C can also conduct purely analogue audio signals. The so-called "Accessory Mode" should no longer be available in modern smartphones and laptops. It was considered a temporary solution until digital signal transmission had gained a foothold and is proving to be another stumbling block when it comes to the topic of USB-C and audio. If you order cheap USB-C headphones or dongles from a Chinese wholesaler, they will most likely not work because of this.

Why USB-C is actually great

If I get over my "negativity bias", USB-C makes sense. The big problem with analogue signals is that they are very susceptible to interference. Maybe you've already had a slight hiss or strange sounds on your analogue headphones and had no idea where it was coming from. It is usually the very delicate, densely packed cables in smartphones, laptops or other devices that have a sensitive effect on the analogue signal. This problem is eliminated with digital signals. It makes sense to go digital for as long as possible and only convert the signal into an analogue signal just before the ear. If this works one hundred per cent and flawlessly, it is the future. It obviously doesn't today. Perhaps also because the future is wireless in the eyes of the manufacturers. Keyword Bluetooth. But even this wonderful wireless world is full of pitfalls: batteries run out or Bluetooth connections are unstable. That's why I don't even open this barrel. I want to plug in my headphones and they work, that's it.

That's why I mourn the analogue connection. I'm happy to put up with a bit of noise on the headphones if they always work. Of course USB-C will prevail. That's bad for customers. They can't be sure that the same connection will actually work. Hopefully, a consensus will emerge in the long term about how USB audio should work. Until then, however, I will stick with the 150-year-old jack technology wherever possible.

Which dongle is it?

To solve my problem, I need a dongle that converts USB-C to 3.5 mm jack. This was not included. I have therefore obtained the four best-selling dongles and will test them in the next article. If you click on "Follow author", you'll be notified as soon as the dongle article is ready.

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Simon Balissat

Teamleader Editorial

Simon.Balissat@digitecgalaxus.ch

When I flew the family nest over 15 years ago, I suddenly had to cook for myself. But it wasn’t long until this necessity became a virtue. Today, rattling those pots and pans is a fundamental part of my life. I’m a true foodie and devour everything from junk food to star-awarded cuisine. Literally. I eat way too fast.

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