Vintage Digital & Analogue Studio Effects

Product Review

Focusrite Scarlett 18i20 Gen 3

Focusrite Scarlett 18i20 Gen 3 Review

Review Introduction

This review of the Focusrite Scarlett 18i20 Gen 3 Audio Interface is not going to be a traditional review as we will not be testing it for the quality of it’s microphone pre-amps etc. Instead we are reviewing it from the point of view of using it to interface outboard effects with a digital audio workstation.

The Focusrite Scarlett 18i20 Gen 3 Audio Interface is the latest iteration of the top of the line within Focusrite’s Scarlett series of audio interfaces, aimed at the home studio user. Focusrite claim to offer 18 inputs and 20 outputs for the Scarlett 18i20 with 24bit/192kHz converters.

Focusrite claim this model has the best ever mic pres to appear on a Scarlett series product, so it looks like a good proposition for the home studio musician to use as the core of their DAW based recording setup. A new AIR feature on the mic pres modifies the frequency response of the input stage to model the classic, transformer-based Focusrite ISA microphone preamps.

Focusrite Scarlett 18i20 Gen 3

In addition to those good microphone pre-amps, and there are six of them in total on the rear panel, the Scarlett 18i20 also features to more dual purpose mic-pre/instrument inputs on the left side of the front panel. So in total you could mic up 8 instruments with the Scarlett 18i20. This is plenty for most home recording setups. On the right side of the front panel there are two headphones outputs, each with their own volume control.

Heading round back, along with the aforementioned mic/line inputs, you have 8 line outputs, S/PDIF in and out via coaxial connectors, word clock out, and dual ADAT inputs along with dual ADAT outputs. Finally, MIDI in and out, and the USB C connector.

Back around the front, each input has an attenuator and a 10dB PAD switch. The first two inputs also feature a mic/line switch, and there are two ‘bank’ switches to add 48 volt phantom power to the mic pres, one for channels 1-4 and the second for channels 5-8. This is not ideal as individual selection would be much better, however this is one of those compromises of a budget interface.

Some nice touches include the ability to not only mute the master outputs, but to also DIM the master outputs, which simply puts an 18dB attenuation on the output to your speakers, this is a great feature that I find very useful.

The front panel also includes a microphone, which you can see as a little pin hole between the two front panel mic inputs. This is used as the talkback microphone to allow communication to musicians you are recording, by using the momentary talkback switch on the right side of the interface.

Finally, there are 8 LED meters for monitoring signal from the 8 inputs. These are very low resolution meters with only 5 steps from -48dB to 0dB. Not great, but better than nothing.

Sound Quality

While the Focusrite Scarlett 18i20 Gen 3 offers 24bit/192kHz converters, that is no guarantee it sounds good. The AD/DA audio chain is dependent on far more than the chips used for the conversion. The analogue stage prior to the AD conversion, and the analogue stage after the DA conversion is critical to any good converter and for the price point this converter sits at, it is pretty good.

As stated earlier, I bought this interface to use for sending out to my rack of hardware effects, and bringing the effects back into my DAW. That is primarily how I use the interface, as well as for straight two channel stereo playback of music. For both of these use cases, the Focusrite sounds great. Yes you can get better for more money, but that is the case with most things, however you do get into the land of diminishing returns the more you spend. I think for many people with a home studio setup, the Focusrite will fit in quite nicely and you would be hard pressed to find fault with it sonically.

Problems In Use

When I researched which interface to buy for the sole purpose of interfacing my hardware effects, my main criteria was for 8 inputs and 8 outputs, allowing me to interface with 4 stereo effects units. The Focusrite ticked that box. plus it had two headphone outputs, I needed one so it ticked that box too.

The first time I went to use those headphone outputs however, I learned the reason why ‘affordable’ interfaces are what they are…compromised. Here is the big downfall of these affordable interfaces, they have a limited number of converters, so to be able to use the headphone outputs, it ‘steals’ the converters from one stereo pair of line outputs. If I wanted to to use the second headphone output it would ‘steal’ another converter from yet another stereo pair of outputs on the back!

By doing this, it makes it a very limited interface. You can have 8 line outputs, with stereo monitor output, or, 4 line outputs with stereo monitor outputs and two stereo headphones outputs, take your pick. You can not have both.


The Focusrite Scarlett 18i20 Gen 3 is a good sounding interface, it really is. For the home musician, I see no reason to spend more on an interface when it is primarily just you working on tracks within your DAW. Home studios tend to use the inputs more than the outputs so the limitation of the number of converters within the Focusrite Scarlett 18i20 Gen 3 may not present as a problem.

I do however have a real issue with Focusrite not advising potential purchasers of this limitation with the design of the Focusrite Scarlett 18i20 Gen 3. Nowhere on the their website page for the Focusrite Scarlett 18i20 Gen 3 do they mention this, not even in the specifications. Simply saying it has 20 outputs, leads me to believe I can use the 8 line outs, stereo monitor outputs, and two stereo headphone outputs all at once with room to spare. But alas, it does not.

I do not think Focusrite are alone in this deceptive marketing.  After looking around, I think most of the affordable interfaces share this same limitation and it makes no sense at all. If I had known this was the limitation, I would have spent more money and bought their higher end interface that did not suffer from this limitation. Choose your interface carefully to suit your needs, and ask questions before purchasing.

Review Summary

I find myself torn between recommending the Focusrite Scarlett 18i20 Gen 3 and telling you to look elsewhere. When you claim as Focsurite does “20 outputs of incredible sound quality” I would assume you are referring to the analogue outputs given that a digital signal is simply being passed through. That is why I never thought their would be compromises with the headphone outputs stealing the line output converters, who would? My use case is not the norm, but I am sure I am not the only one who will in fact make full use of all inputs and outputs, only to find they can not use the headphone outputs as well. This is a major limitation and Focusrite along with all other manufactures should be called out on it. Be more upfront with your customers to avoid customer disappointment. Like I said, I would have spent the money for the higher end interface had I known, instead, I have to now sell this interface at a loss, and buy another interface that does not have this same compromise…it will not be another Focusrite.


  • Good sound quality
  • Good build quality
  • Functional front panel layout


  • Limited functionality for those wanting to use all outputs
  • Somewhat deceptive marketing



Build Quality 90%
Sound Quality 90%
Ease Of Use 80%
Usefullness 70%
Value 85%

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