Essentail tips for using two audio intefaces
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Have you ever wanted to use two or more audio interfaces together? Maybe you need more inputs than your current sound card provides or you want to make use of newer features but don’t want to get rid or your old device. Regardless of the reason, installing multiple audio interfaces in a single system might seem like a good idea. 

Or does it? Many types of recording equipment are known for being finicky, and some audio interfaces definitely fall into that category. If it was that easy to use multiple interfaces together, why aren’t more people doing it? 

The fact is that using more than one audio interface in a recording computer can be fraught with challenges. Hardware and driver conflicts, glitches, latency, BSODs…all these can put a damper on any recording session. 

But if you are willing to take a chance and want go where relatively few brave souls have gone before, read on…

Can you use two or more audio interfaces together?  

The short answer is: “Yes.” You can use two (or, theoretically, more) audio interfaces together in the same computer and have them be recognized by your DAW. But like many aspects of recording‒particularly computer-based recording‒you will have to do a bit of configuring to make it work. 

Even then, there is no guarantee that everything will work flawlessly. Keep in mind that you’re trying to get two (or more) devices working together in the same machine, relatively few of which are designed to do. Although you could get it to work in theory, be prepared to go through a bit of setting up, trial and error, and head-scratching in the process. 

The simplest and easiest way to go about it is to use audio interfaces that are designed to work together. Manufacturers such as Focusrite, Adent, and Presonus have models that allow you to use as many as four devices at once. These would typically be identical interfaces, although you could also use different units from the same line and generation.  

These audio interfaces use proprietary multi-device drivers. This means that they will only work with identical or similar models from the same manufacturer. 

Interestingly enough, many newer models don’t support multi-device drivers. In some cases, this feature is promised in a future driver update, but you can’t always tell when it is finally implemented. If you have a couple of units for which multi-device driver support is promised, it would be best to contact the company directly to find out if it is finally implemented with a new driver release. 

If you have two or more audio interfaces from different manufacturers, there are a few solutions to get them to play nice with each other. 

If you are on a Mac, the good news is that that CoreAudio supports aggregate devices natively. This capability allows you to use two or more interfaces together as a single device, even if they are from different manufacturers. 

Although CoreAudio works well enough for most devices, keep in mind that it isn’t a guaranteed solution. Some interfaces may not cooperate, resulting in clicks, pops, or crackles. Some audio interfaces may not even be recognized by your DAW when using Core Audio along with another device. 

Things are a bit more complicated if you are on a Windows PC. While many native Windows audio drivers (MME, WASAPI, and WDM) support multiple devices, the latency can be too much for practical recording purposes. And because DAWs can only use one audio driver at a time, you would typically be limited to only a single audio interface. 

But there is a solution; ASIO4ALL. This cleverly named bit of code was primarily designed to allow for low-latency operation, even with consumer soundcards. But it also brings together multiple audio devices into a single aggregate device, much like CoreAudio on a Mac. 

The downside is that any devices you use in this fashion will have higher latency than when used individually with their dedicated drivers. For some users, though, this is an acceptable tradeoff for the ability to use multiple audio interfaces

Why would you want to use multiple audio interfaces? 

Why would anyone want to use more than one audio interface in the first place? Shouldn’t one be enough? 

To be sure, you can get a lot done with even just a basic interface. In a typical home studio setting, you probably record only one or two audio sources at most, usually a guitar and a vocal. For such applications, even a basic single- or dual-input device would suffice. 

But what if you want to record more than one audio source at a time? Say, an acoustic duo, a horn or string section, backup singers, or even a small band? If all you have is a 2-input audio interface, you’d have to record each one separately. 

On the other hand, if you have an extra audio interface, you could press it into service using one of the methods outlined above. In this particular scenario, using two or more audio interfaces together is a great way to add more inputs to your setup. 

You might also want to take advantage of recent developments in recording technology, such as better quality preamps and built-in digital signal processing (DSP) capabilities, which you may not have with your current interface. Rather than leaving your old interface unused, you could simply keep using it along with your new acquisition. 

You may also want to use different interfaces for different tasks. For instance, you might have a model with better mic preamps and one with better support for a particular piece of software. You might also want to use yet another soundcard for its onboard DSP or synthesis capabilities. 

Using two different audio interfaces also allows you to record the output of one device into the other. This is a useful capability for adding voiceovers to instructional or tutorial videos or ‘sampling’ the output of a standalone software synthesizer into your DAW. Some audio interfaces do allow you to accomplish these tasks with ‘loopback’ recording (more on this later), but using two audio interfaces is still an option. 

Of course, you could also opt to purchase a new audio interface that combines all the features you need in a single package. But given such diverse requirements, it can be challenging to find such a unit, particularly on a strict budget. And if your older devices still work perfectly, it would be a waste to toss them in a closet if you could somehow get them to work together with each other. 

Drawbacks of using multiple audio interfaces 

In a perfect world, you could simply install two or more audio interfaces in your computer and have a powerful and smoothly performing music production/recording system. If only things were so easy…

The truth is you are likely to run into some obstacles even if you have multiple devices that supposedly work well together with a single driver. And if you add third-party solutions such as ASIO4ALL into the mix, things can get even more troublesome. 

The most common drawback to using multiple interfaces together is higher latency. This refers to the time it takes a signal to travel from the input of your interface, through the DAW or signal processing software, and out to your speakers. 

With a good interface and the appropriate drivers, you can get latency down to negligible amounts. This means that when you sing into a mic plugged into your interface, you can monitor it practically in real-time. Of course, there will always be a bit of delay given the nature of computer-based processing, but it will hardly be noticeable if your system is set up correctly. 

But when you use two interfaces together, you will likely experience higher latency. Furthermore, the problem will probably get worse the more interfaces you use. 

Multi-device drivers such as ASIO4ALL also have their own issues. In some cases, multiple devices can conflict with each other, resulting in crackles, stutters, glitches, and other anomalies. I’ve even come across situations wherein one or more devices require repeated restarts or don’t work at all. 

Don’t get me wrong‒ASIO4ALL is great when it works, But it isn’t a ‘magic bullet’ that will work for every conceivable scenario. To its credit, it is free, so you have nothing to lose by trying it out. If it turns out to be problematic with your particular system, it would be best to try other options. 

How to set up your system to use two audio interfaces 

So now that you know that using two or more audio interfaces simultaneously could work, how do you go about setting up your system? Here are some tips: 

  1. A good rule of thumb is to install the older device first. This ensures that any drivers you will install later will always be the latest version and that it won’t be overwritten by an older driver. In addition, this will reduce the risk of driver conflicts and incomplete installations.
  1. Make sure that your operating system supports all the audio interfaces you plan to use. If a particular unit doesn’t work with your system on its own, there is no way that it will work as part of a multiple interface setup. 
  1. It goes without saying, but make sure to install the latest drivers for all the devices you plan to use. Whether you use the manufacturer-supplied driver for multiple identical devices or you want to give ASIO4ALL a try, installing the latest drivers will minimize potential problems.
  1. Once you have all the necessary drivers installed, set up your multiple-device driver. The driver should have a control panel where you can activate the inputs and outputs of each device you will use.
  1. Here’s a tip: disable any I/Os that you don’t need. For example, if you’re using the audio capabilities of only one of your devices, you can disable the I/Os of the other devices to prevent possible conflicts. This could also help reduce the noise from unused open inputs. 
  1. Check to see that all the necessary I/Os pass signals properly. If you are using several inputs from different audio interfaces, make sure that they capture audio without unwanted noise or glitches. All open outputs should perform the same way. 
  1. Finally, pay attention to how your system performs with all the interfaces active. There should be no noticeable lags or stutters. If everything seems to be working properly, you’re in business!  

Alternatives to using multiple audio interfaces 

Let’s say that it isn’t possible to use multiple audio interfaces in one system. Maybe the devices you have conflict with each other or they simply don’t work together with a single multi-device driver. Or you only have a single audio interface. What then? 

There are ways to get the functionality of a multi-interface setup, even with a single device. For starters, you could use the loopback feature if your device supports it. This allows you to capture audio while another source is playing back. So, for example, you could record the audio track of a training video along with your voiceover. 

Check out this article for some more information about loopback capability

Some audio interfaces support loopback natively, but many newer devices don’t have this feature. Some audio interfaces that have loopback capability are:

  • Scarlett 3rd Gen 4i4, 8i6, 18i8 and 18i20 
  • The Audient iD4 and iD14 (MKII) 
  • Presonus Studio 24c

Another option is to add more I/O to your audio interface. If your device has an ADAT port, you could connect an expander unit that essentially gives you more physical inputs and outputs. Some audio interfaces that have ADAT connectivity are: 

  • Focusrite Scarlett 18i20 
  • Focusrite Clarett 8Pre 18×20
  • PreSonus Studio 192
  • RME Babyface Pro FS
  • TASCAM US-20×20

The bottom-line

There you have it. That’s pretty much everything you need to know about using two or more audio interfaces together. It can be challenging to get everything set up and working without any issues, and you will likely have to go through a lot of trial and error, not to mention disappointment and frustration. But when it all comes together‒and there is a good chance it will‒the benefits can be considerable. 

Good luck and have a great recording session! 

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