What Cables Do I Need for Recording? - Part 2: Digital Cables

Updated: Feb 20

I swear. Sometimes I surprise myself at how bad I am at graphic design.

Alright audio friends. My posting has not been as frequent as I hope for it to be.


The main reason is that I’m currently finishing up on what’s turning into an epic eBook (should that B really be capitalized? I trust the robot spellchecker at my own peril) - which I will be giving away to all of you fo' free (in the parlance of our times).


I’m not talking about a 5 page PDF with information you already knew. I’m talking…EPIC. The working title is "How to Record Your Band". Pretty straight forward. More on that later.


For now, let’s pick up where we left off: the exciting world of audio cables – The High Speed Infrastructure of Every Studio!


In the last post, we talked about analog cables. The cables help transfer analog signals from one point of our processing chain to the next.


Next up are digital cables.


Digital cables help us transfer signals that have already been converted to digital. The most common applications are:


  1. The connection between your interface and your computer. The interface has an A/D (analog to digital) converter and it’s able to take our sweet mega-riffs from a mangled analog waveform to a bunch of 1s and 0s that emulate the waveform. We need this signal to be digital because our computers only process digital data (for now).

  2. The connection between your interface and additional preamp channels that you are “chaining” together. Interfaces often give us the capability of connecting other digital sources into them. Think of this is transportation hub where different signals can meet up and take the same train over to the computer. For example, you may have an interface that does its own A/D conversion. You can then take that digital signal, route it to your interface and piggy-back onto whatever digital outputs the interface is generating onward to the computer. This type of thing is helpful for expanding the number of inputs you can work with. For example, I use an Apollo Twin interface – which only has two on-board pre-amps. However, I also have a UAD 4-710d preamp which gives me an additional four preamps channels and does its own A/D conversion. I connect the 4710d to the Apollo Twin with a digital cable and all of that data runs to the computer from the Apollo interface via a single cable.

  3. The connection between a controller (e.g., MIDI controller) and your computer

  4. Connections between an instrument with a digital output and your computer (e.g., synth, keyboard, guitar with digital output, etc.,)

The decision on digital cables is typically very straightforward and made for you by the manufacturer of the output gear.


You remember that thing you threw back into the box and tried to recycle? It’s called the manual and you should have read it.

Usually, just by looking at the connector type, you’ll be able to understand which type of cable to use.


Things get a little murky with digital signals because you can have different "protocols" through the same connector. I’m not going to get into the details of digital protocols (in part because my understanding of it is limited!) but you can think of a protocol as the set of rules by which the digital devices transfer and receive data. It’s kind of like a secret handshake that they both need to know in order for the data transfer to work properly. Anyway, for the most part, if you just match the connection types (e.g., ADAT to ADAT) you won’t have any problems. In this way digital is remarkably simple to work with.


Here are the most common types of cables/protocols:

ADAT - Famous for being willing to let people "make up their own acronym". Mine is "All Dogs Act Tough".

ADAT – Fiber Optic Connection

This is one of the more common types of digital protocols in the studio. It is a light-based transfer that takes place through fiber optic cable and a connector called TOSLINK.


S/PDIF – Sony Phillips Digital Interface


S/PDIF - Let's go with "Successfully Playing Djent In Florida" (no trivial task)



An RCA or TOSLINK connector used to transfer a (usually) compressed signal over short distances. Note the TOSLINK is the same connector as was used for ADAT but the hardware will say S/PDIF next to the connector if that’s what’s being used. You're mostly likely to run into this if you're transferring audio from a consumer audio system into your recording rig.



USB – Ah the good old Universal Serial Bus

Good for everything from your wireless mouse to transferring 16 channels of drum mics as your half-deaf drummer works his hardest to destroy another set of drum heads
USB 2 - White or black inner plastic piece

It’s important to note here that when we say “USB”, we are referring to USB Type A – which is the connector most of us are familiar with. While Apple used Firewire (and was one of the first manufacturers to adopt Thunderbolt), most PC users were using USB interfaces. In recent years, USB has moved onto USB 3 and 3.1.





You can tell a USB 3 port from a USB 2 port because a USB 3 port will be blue on the inside.

The interesting thing about this is that while USB 3 has roughly 10X the bandwidth of USB 2 (USB 3.1 gets us up to 3.1Gb/s) , it does NOT decrease your latency.





Mostly Relevant Side Note 1 - Latency:

Latency is that little delay between when you play a note and when you hear that note back as it travels through the interface and A/D, D/A conversion processes.

How can this possibly be? It’s 10X more bandwidth but the same amount of latency? Well the problem is with how USB ports interact with the processor. I’m not an expert here but I saw a good analogy that crystallized it for me. More bandwidth but no change in latency is like having a larger delivery truck but still being stuck in the same I-76 expressway traffic (Philly, that one’s for you!).


Sure you have a cooler car but who cares?

In other words, you can carry more packages but you won’t get to your destination faster. So, you can work with more channels of audio but you’ll still have latency. The thing is that for most DIY recording projects, USB 2 provides plenty of bandwidth so USB 3 may not offer a huge advantage. For example, working with a 48kHz sampling rate and 24 bit audio will allow for somewhere around 80 channels of audio with USB 2. Do you need more than that? I don't know. How many toms is your drummer insisting on close-miking?





Firewire – Like USB but for Apple and Discontinued


Firewire. What a cool name. Alas, they used it too soon.



It was discontinued in 2016. At this point Firewire is pretty much obsolete and I’m not going to talk about it.






Thunderbolt – OK. Thunderbolt is where it’s at


You can tell it's Thunderbolt by the lightning bolt. What's that? There's already a connector called Lightning you say? Whatever. I guess "Thunder" is hard to draw.

Thunderbolt 3 connections (now on both PC and MAC) have ridiculous bandwidths (at 40Gb/s it’s got another 4X or so on USB 3.1) and, because of how they interface with the motherboard, virtually ZERO latency. This is a game changer and will be ubiquitous within a couple of years in the audio world. Thunderbolt uses the cool, new USB-C connector which can be connected in any orientation (unlike previous USB connectors) and can handle additional power capacity (which will allow for some improved charging-while-data-transfering on your other devices).


The crazy thing is that as of right now, you can actually get a Thunderbolt-enabled interface for less than you can get a USB 3 interface. I think this is just because people haven’t upgraded to Thunderbolt-enabled computers yet so the demand isn’t there. This means that now is a great time to pick up a Thunderbolt interface if your machine has the ports for it.


A Friendly Warning Note: with digital signals, it is advisable to mute the inputs or even turn the equipment off when making connections because first making that connection can lead to a signal spike.


Alright, that does it for digital connectors.


On a final note, I'm currently offering to do one, free test mix for artists who have stems. Email me at vk@calmfrogrecording.com or reach out via the website www.calmfrogrecording.com for more information.


Cheers and happy recording!

Vadim