So you’ve upgraded from an iPhone and AirPods to a legit HiFi audio system, but rather than simply tapping a button, you’ve got a number of wired connections – some of which you’ve never seen before – and you need to get everything right before you can enjoy your new gear.
In any digital audio chain, you’ll have a source (the device that’s playing back the music), a DAC (the device which converts the digital signal into an analog one), amplifier (a device which increases the volume of the base analog signal), and your final output (speakers or headphones). In some cases, all those devices might be integrated into one or two pieces, rather than four – and in others you might separate things out even further, with multiple amplification stages. But if you want to listen to digital music, each of those functions must be fulfilled.
For each function, you need a device to accomplish it, and for each additional device, you’ll need cables to connect them. Depending on your exact setup, you may need different sets of cables or connections. If you’re using a portable digital audio player, all you need to do is connect it to the wifi, and get listening, but if you bought a separate DAC and amp that will also need to be connected to a source, it’s going to be a bit more complicated.
Any digital audio setup is going to start with a digital connection. The digital source you’re using will determine what kind of connection you’ll use with it. While PCs, tablets, and phones will typically use some form of USB, many streamers, CD players, or Blu-ray players use digital coax, optical, or even AES. So what’s your best option for connecting a digital source to a DAC?
In modern, streaming focused, all digital systems, USB is probably the most common type of connection. Before the introduction of USB-C, virtually every USB cable had a different connector on each end: typically a USB-A that would connect to your computer, and any other number of terminations to connect to an accessory. There were various standards like microUSB and miniUSB along with proprietary connectors that only worked for one manufacturer’s products.
Thankfully, we’ve eliminated a number of proprietary connections along with miniUSB and (mostly) microUSB as well, with most portable devices standardizing on USB-C in the last few years. The creation of the USB-OTG (On The Go) protocol also provides a standard way for any portable device to connect to an external accessory.
When in comes to the current crop of devices, there are 4 types of USB connections that you’ll typically find on digital sources:
- USB-A is found on most desktop PCs and laptops. It’s the oldest and most enduring USB connection.
- USB-C is the latest USB standard, and is the standard for tablets, Android phones, and is becoming more common on PCs and laptops as well.
- Lightning is a proprietary Apple connection that’s found on iPhones and some iPads.
In addition, there are a handful of connections that you’ll find on the other end:
- USB-B is most famous as what’s on the other end of your printer cable. It was designed specifically to plug into accessories with a USB-A on the other end of the cable.
- USB-C goes both ways – so you’ll have the same connection in your source as in your DAC.
- microUSB is on life support at this point, with a very small number of manufacturers using it – seemingly more on principle than anything else.
The last piece of the USB equation is the USB-OTG protocol. Most portable devices are designed to connect a charger or to connect to a computer as an external hard drive for transferring files. In order to connect to an accessory, like a DAC, you’ll need a cable or adapter with OTG built into it. Perhaps the most famous OTG adapter is the Apple Camera Connection Kit, but there are a number of other options from a range of portable devices.
Other Digital Connections
While it might be hard to imagine, digital audio is older than USB, and so in the age of CDs, MiniDisk, and DAT, the Sony/Philips Digital Interconnect Format (S/PDIF) was used to transmit digital signals. Along with that, TosLink was pioneered by Toshiba and piggybacked off of S/PDIF technology with a design made from the ground up for HiFi CD Players.
The standard S/PDIF connection is Digital Coax. Digital Coax cables use the same terminations as analog RCA cables, but have a different impedance and are designed to carry a digital signal. There’s also a Coax Mini connection which is used on some portable devices. This uses a 3.5mm/mini headphone connector on one end with the standard RCA style connector on the other. While USB has the most variations, the fact that Digtial Coax exclusively uses terminations for digital connections that look exactly the same unrelated analog ones, makes it possibly the most confusing of all connection types.
TosLink connections, also known as “optical digital,” use the same protocol as S/PDIF, but transmit the signal via light pulses rather than electrical ones. Because it relies on the transmission of visible light, TosLink is more limited in terms of the maximum bitrate, and in cable length than other digital connections.
AES/EBU is a professional standard which was designed for transmitting digital audio across very long distances. AES stands for “Audio Engineering Society” and EBU for “European Broadcast Union. While consumer audio connections can start to degrade in distances of as little as 10-20 feet, AES is designed to deliver signals at distances over thousands of feet. Because of the incredible signal integrity, many “prosumer” products or those marketed to both professional and consumer applications – and some high-end consumer products – adopted AES as an option. AES typically uses a 3-pin XLR style connection, but for the longest distance it uses a BNC/Coaxial connection.
So… How should I connect my source to my DAC?
All things considered, USB is the best possible option, and it’s also the most commonly available. If you’re using a portable device, USB-C or Lightning is going to offer the smoothest experience and the best bitrate in most cases. While older USB devices may be more prone to RF interference than S/PDIF, anything using the latest protocols or USB 3.0 will have no measurable difference in distortion or interference when compared to S/PDIF. AES is prefered for long cable runs, and it can be more resistant to RF and noise than other standards. Typically the only reason to use S/PDIF or TosLink to connect your source to your DAC is because you don’t have any other options.
Any connection that comes after your DAC will be analog. Once you have the digital end all worked out, things get a bit simpler on the analog end. While there’s no way to adapt USB to S/PDIF (without fully converting the signal), any difference in analog audio is basically just a question of “how many wires am I splitting the signal up into?”
In the HiFi world, an analog signal is either single-ended, or balanced. A single-ended signal is the most basic form of a stereo signal: one wire for the left channel, one wire for the right channel, and a ground. Balanced steps things up, adding positive and negative ends of the signal for left and right. The most common single-ended analog interconnects are RCA and 3.5mm, and the most common balanced ones are XLR and 4.4mm.
Outside of bare wire, RCA connections are probably the oldest type of audio connection still in use today. They came to popularity in the 1930s and 40s where they were used in radio production studios and eventually home record players. Typically they’re found in pairs, with each cable carrying a mono signal in the main plug with an outer shield that carries the ground.
3.5mm cables are among the most common ones out there, and before the age of Bluetooth, there was a period where it seemed like almost everyone had one handy to connect to their iPod to the auxiliary input in their car. While they’re not as common as RCA to use as an interconnect, many devices still use a 3.5mm cable for a line out. You may also use a setup with a hybrid of RCA and 3.5mm, which enables you to connect the phone or line output of a portable device or computer to the RCA input of an amp, AVR, or set of powered speakers.
The original balanced audio connections were developed in studios to help reduce the interference caused by the massive amount of electromagnetic interference that can be generated by all the racks filled with effects, amps, and other signal processors in a well-equipped studio. Rather than use a single XLR cable to carry left, right, and ground signals on its three pins, a balanced cable would use two XLR cables to separate out the polarity and ground for left and right. Modern studio and HiFi gear continues to use dual 3-pin XLR cables as one of the most common balanced standards.
One thing you might notice reading through this guide is that new standards in audio don’t present themselves very often. So far, outside of USB (which is still more of a general electronics technology than an audio specific one), the newest of these connector types we’ve mentioned is 40 years old. The balanced 4.4mm Pentaconn connection is the newest addition to the fold, having been created in 2015 (it’s even a full year newer than USB-C). A 4.4mm interconnect allows you to provide the same balanced signal as an XLR, but with just a single, more streamlined cable.
So… How should I connect my DAC to my Amp?
Generally speaking, if there’s a balanced connection option between your DAC or digital audio player and amp, it should be your first choice. 4.4mm and XLR have the same benefits of providing an electrically superior signal and preventing interference – and there are options available to adapt between the two. Otherwise, there’s a reason that the RCA standard has endured for so long, and while there is a measurable difference between balanced and unbalanced with more devices, a high quality set of RCA cables can provide an experience that’s indistinguishable from balanced for most listeners.
Getting your equipment connected
So, basically, if you’re looking for the best way to get everything connected, start with your source, figure out the best digital connection to use to connect to your DAC, and then the best analog connection for amp. Using balanced connections and higher quality cables will help improve the signal quality, and reduce the potential for interference and noise, but for the most part, once you’ve got everything set up, you can forget about the cables and just enjoy the music.