Saturday, May 18, 2024


There are lots of two-channel digital audio interfaces to choose from for your personal studio needs. UK based SSL (Solid State Logic) is one of the oldest pro-recording brand names with roots stretching back to 1969; they are best known for their big, mega-expensive, studio mixing consoles which dominated pop music throughout the 1980's. Several of those big, heat producing beasts are still making hit records by producers like Chris Lord-Alge and Vance Powell. 

So when a company like SSL decides to release a comparatively inexpensive 2-channel digital audio interface, we've got to know, is it any good?

There are actually two inexpensive models SSL offers, the SSL 2 and the SSL 2+. I bought the SSL 2+ because having two independently adjustable headphone amplifiers was important to me. I often have someone listening along with me on a second set of headphones and those individual headphone level controls allow us each to have the most comfortable volume for critical listening. 


All the inputs and outputs are on the rear of the SSL 2+. 


There are two combo-XLR/TRS input jacks. The TRS hole is used if you have an unbalanced musical instrument or a balanced line level source that you want to input for recording. The XLR connections are used for feeding professional studio microphones into the interface. 


Next to the input jacks are two 1/4” TRS balanced output jacks which are meant to connect to a pair of powered speakers. If you'd rather use unbalanced outputs there is a pair of RCA/Phono jacks next to the 1/4” connections. A second pair of RCA/Phono outputs is provided which represent two additional output channels numbered 3 and 4. To feed these jacks you'd need to run a DAW or some kind of sound application on a connected computer which gives you the ability to assign audio output through these two unbalanced channels. (Note: The cheaper SSL 2 does not have any RCA/phono outputs.)


Next to the RCA/phono jacks are the two 1/4” headphone output jacks designated A and B.


The SSL 2+ has two five-pin Midi connectors, one for input and one for output. I appreciate the standard legacy 5-pin connectors which don't require any adaptors. The Midi input makes it easy to plug in any legacy keyboard controller and play virtual synthesizers. 



A USB-C type connector is provided for making a connection to a computer. This USB connection runs at the slower USB-2 speed but features a modern “C” type connector. USB-2 is more than adequate for handling two streams of digital audio regardless of sample rate. The interface includes two USB cables, one goes from type C to type C and the other goes from type C to type A for connection to older USB gadgets (like my Mac Pro cylinder computers :-).


The standard Kensington Lock slot is provided for anchoring the interface to prevent theft. 



The big blue knob is the output for a pair of powered monitor speakers. 


The two headphone outputs on the rear are controlled by two independent black knobs. Headphone A carries the same signal as the speaker outputs (the headphone level is not affected by the speaker volume knob). Headphone B volume output is controlled by the black knob labeled B; Headphone B also features an optional pushbutton which allows it to receive the same signal routed to the RCA/phono jacks 3 and 4. 


The MONITOR MIX knob is like a balance control, it allows you to listen to "interface only" or pan to the live microphone inputs or any mix location that allows you to sing and hear yourself with zero latency, mixed with audio from your DAW. It's a simple and effective way of recording without latency using a microphone. 

The button marked stereo controls whether you hear your sources in mono or stereo for clarity. Refer to the users manual for some detailed instructions. In normal use for monitoring your computer output you'll want this knob panned all the way to the USB side.


Also on the front panel are the controls for the inputs of the SSL 2+. You can plug in almost any type of professional microphone. Independent, switchable 48-volt phantom power is available on each input and they can be switched for line or instrument (input level and impedance). Each channel has a small 5-segment LED ladder to show the level feeding into the computer. Two red Gain control knobs adjust the gain of the built-in microphone preamps. Beneath each Gain knob is a pushbutton switch labeled 4K, which “allows you to add some extra analogue 'magic' when you need it” (quoted from the user guide).


The 4K button adds a bit of distortion and treble boost to your microphone input signal. Personally I avoid using this feature because, once it's recorded on your song, you can't get rid of it. There are countless pieces of plug-in software that give you similar effects and you can choose to add them later in whatever amount you want. 


The SSL 2 – series is clearly meant to bring the SSL brand into low cost home studio situations. While there are no real problems in the design of the SSL 2+, it feels much more like a lightweight plastic Allen and Heath product (SSL sister company) rather than a classic SSL design. The knobs and switches remind me of my previous A&H 436 mixing board. The specifications are downgraded from what we've come to expect from SSL products (limited dynamic range, distortion measured at low operating levels, nowhere near the +27dBu output capability of higher end SSL gadgets, molded plastic enclosure). In spite of these caveats the SSL 2+ could easily be used to create a pop-music recording in your back bedroom and it is vastly superior to the recording gadgets I had back in 1968.


Like I usually do before I buy something, I downloaded the manual for the SSL 2+ from the SSL website and familiarized myself with the connections and capabilities. The full “User Guide” has lots of diagrams and details about connecting your gadgets to get the most performance. It also contains detailed “Audio Performance Specifications”. 



  • Pleasant sound quality
  • Easy to use
  • USB bus powered so no wall wart or line lump power supply
  • Zero latency recording monitor using dedicated hardware MONITOR MIX knob
  • Good headphone amplifiers
  • Adequate preamp gain for ribbon mic use
  • Big volume knob for speaker volume


  • No phase reverse switches on mic inputs
  • No input pad options
  • No insert points after preamps for analog processors
  • Maximum output level only +12.5 dBu
  • 4k Switch 


I have an audio/video workstation in one of our creative studios (the 'Kitchen') where I've been using the SSL 2+ interface every day on a 12-core Intel Mac Pro. The balanced audio output from this interface drives a bi-amped Presonus monitor system with ease and after six months of 24/7 continuous use it has been totally reliable. I've used various Audio Technica, Beyer and Sennheiser headphones including the HD600 and HD650 models and never come up short on volume or tone. 

The SSL 2+ balanced outputs replaced the Mac Pro inbuilt audio outputs and it's a big step up in sound quality. The SSL also sounds noticeably better than my Gen2 Focusrite 2i2 two-channel interface. This is a very useful, low cost audio interface with no major flaws. It connects and works effortlessly on Apple Mac computers while accommodating almost all professional microphones and musical instruments. 

This would be a great audio interface for producing recorded podcasts and YouTube videos. SSL has created a low cost audio interface that delivers solid performance for todays “in the box” producers.

Thanks for reading High on Technology, Good Music To You!

©May 2024 by Mark King, it is not ok to copy or quote without written permission from the author.