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DSP: What it is and how to use it

Nov 8, 2022 7 min read

Will Hunt

CONNECT 6 DSP

What does it mean for an audio interface to be “DSP powered? In this blog we’ll break down what it means, and how the LEWITT CONNECT 6 audio interface uses DSP to make your life easier in the studio. 

What is signal processing?

DSP stands for "Digital Signal Processing". A signal processor is any device that alters the nature of your audio signal from its input to its output. Types of signal processing can be divided into two general categories.

  • Analog signal processing uses an electrical circuit to modify an audio signal, Examples of analog signal processing are guitar pedals, stompboxes, and physical outboard studio gear like a Fairchild EQ.
     
  • Digital signal processing uses a CPU to process the audio as representative bits (0’s and 1’s). Examples of Digital Signal Processing are the many mixing, mastering, and effects plug-ins you use within a Digital Audio Workstation.  

There are many differences between analog and digital, but for the purposes of this blog you just need to understand that “DSP” is audio processing that’s handled by a computer CPU, rather than an electrical circuit. 

The problem with plug-ins

If you’ve ever run a multi-track session in your Digital Audio Workstation, you may already have experienced the limits of digital signal processing.

  • They're CPU intensive, meaning your computer has to work harder to run your different EQs, compressors, and other effects. Running too much DSP can cause your session to slow down or even crash. 
     
  • They add latency. Many DAWs can compensate for latency by adding a counter-delay or “buffer” to ensure all the tracks play back in sync, but this doesn’t help if you are recording something into the session. You’ll experience a delay from when you strike a note to when it plays back through your speakers or headphones. 

Latency is the increase in the time it takes for an audio signal to travel from your input source to your speakers.

But there’s another workaround, and that is to use a separate CPU to handle the processing instead of relying on your computer. See where we're going with this? 

How to use DSP in CONNECT 6

CONNECT 6 includes three DSP plug-ins to help you get a clean, polished signal while recording. These plug-ins live on inputs 1 & 2. You can set them yourself, or you can use AUTO SETUP to configure them automatically. These plug-ins are powered by the CPU in CONNECT 6, so they will not incur latency in your session. 

Read on to learn the DSP tools at your disposal in CONNECT 6.

CONNECT 6 expander

Expander 

The expander might become your best friend if you have a noisy recording environment. These tools can be used as gates that can remove a variety of low-level noises, such as:

  • Air conditioners
  • Refrigerator hum
  • Low-level traffic noise
  • Instrument noise

Expanders are more commonly used in mixing or live performance situations, but if you have to record in a less ideal environment, an expander can help to clean up your audio. Here's a breakdown of the basic controls:

  • Threshold: Whenever an audio signal falls below the threshold, it gets turned down in level. It's best to set your threshold just above the noise floor.
  • Ratio: When the audio falls below the threshold, the ratio is the amount it gets turned down by. To remove noise, you typically want a high ratio.
  • Attack & Release: This controls how quickly the volume changes occur. 

 

CONNECT 6 compressor

Compressor 

CONNECT 6 has a very flexible compressor to allow you tame transient sources like vocals, guitars or even drums during tracking. Here are some examples of common uses for a compressor when recording:

  • Controlling harsh transients: Some sound sources like percussion or vocal "plosives" can have sudden short volume peaks. Using fast-attack compression can fix these momentary dynamic spikes.
  • Taming dynamic performances: The human voice is a very dynamic instrument. Small changes in performance can result in wildly varying input levels. Using compression, you can control the overall dynamics of a performance to make everything sound more uniform.

When recording, it’s always best to err on the side of lighter compression. You can always compress things more in the mix, but you can’t go backwards. If you are recording vocals, try a ratio of 2:1, a 10ms attack time, 100ms release time, and adjust the threshold to get 2-3 dB of gain reduction during the loudest sections. This is a great starting point for taming the dynamics of a vocalist while recording in a very natural, transparent way. 

Here's a breakdown of the basic controls:

  • Threshold: Whenever an audio signal rises above the threshold, it gets turned down in level. 
  • Ratio: When the audio reaches the threshold, the ratio is the amount it gets turned down by. The higher the ratio, the more extreme the effect.
  • Attack & Release: This controls how quickly the volume changes occur. 

CONNECT 6 EQ

Equalizer 

Equalization is the process of boosting or cutting certain frequencies to alter the overall tonal balance of a source. CONNECT 6’s flexible 4-band equalizer offers a variety of shapes, including shelves, bells, notches, and low/high cut filters, so you can clean up and enhance your audio.  

Here are three of the most common ways to use the CONNECT 6 equalizer during tracking:

  • Apply a low-cut filter. This allows you to remove any subsonic frequency information you don’t want in your recording. For example, for vocals, you can use the high pass button below the preamp gain knob for an 80 Hz low cut filter. This will cut any mic stand noise, plosives or rumble without affecting the fundamental frequencies of the vocal.  
     
  • Notch out problem frequencies. Some instruments are highly resonant in certain frequencies, which can cause issues during mixing. Performing a "sweep" of these frequencies and cutting them with a narrow Q setting is a great way to set yourself up for success in the mix.

An "EQ Sweep" is the process of boosting an EQ band and moving it across the frequency range, listening for any unwanted sounds that occur. Once you've found your target frequency, reduce the gain below negative and adjust your Q to taste.

  • Boost the high end. Some microphones and instruments may sound too "dark" or lacking in high frequencies. Use the Equalizer to solve this problem using the high shelf filter on band 4. Boosting just one or two dB can have a huge effect on the brightness of your audio!

CONNEC6 6 Maximizer

Maximizer 

In CONTROL CENTER, you have two different mix buses, and each of them has a maximizer. A maximizer allows you to increase the overall level of the mix without worrying about distortion from clipping.  

A great use for this tool in recording is to increase the volume of your headphone mix. If you have quiet headphones or are working with a very quiet source, it’s helpful to have an extra gain stage to turn up your monitoring volume without turning up the actual preamp gain and risking clipping the preamps. Maximizer will give you more volume than you need, so you can record with ample headroom. 

Conclusion

If all the information above seems overwhelming, don't worry! CONNECT 6 gives you a ton of options for adjusting your tone, but if you would rather spend more time recording and less time tweaking, you can just use the AUTO SETUP option to have CONNECT 6 intelligently set EQ, compression, expansion, and input gain for you. You can speed up your workflow and get a great starting point for your sound with the touch of a button.

Whatever task you're accomplishing with CONNECT 6, these tools are sure to make your life a lot easier. Any questions? Sound off on social and let us know!


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