HoRNet ChannelStrip 90% off with the code CHAN90 for the next |
What are the differences between the compression models found in the ChannelStrip MK2, MultiComp and TrackShaper?
As you may know, the ChannelStrip MK2, MultiComp, and TrackShaper all share the same core compression technology, with three different models: VCA, FET, and OPTO. Each of these models offers unique compression characteristics that are inspired by some of the most iconic and widely used compressors in history. Even the analog emulation differs from one model to another, making each model distinct in its own right.
Let’s take a deeper dive into each of the three models to better understand their specific sound characteristics and how they work.
The VCA model is the most “modern” sounding among the three and is primarily known for its precise and clean compression. This model is inspired by the Voltage Controlled Amplifier (VCA) found in many large consoles from the 1980s. At its core, there is a linear VCA that operates by compressing audio once the sidechain signal crosses a predefined threshold. The compression occurs in a very straightforward, linear fashion, with a hard knee.
The simplicity of the VCA model is part of what makes it so effective in many situations. However, to avoid the unwanted pumping effect when the compressor reacts to peaks, the sidechain signal driving the VCA is derived from an RMS (Root Mean Square) calculator. In the digital world, calculating the perfect RMS value for any given signal is relatively easy, but in the analog realm, the RMS calculation is far less precise, and this imperfection is part of the charm and character of the VCA model’s sound. This “imperfect” calculation gives the VCA compressor its signature flavor.
When you engage the analog emulation of the VCA model, you activate a waveshaper that simulates the saturation found in AB class amplifiers. These amplifiers are typically used in operational amplifiers, and this addition introduces further warmth and color to the signal. A DC blocking stage is also included to prevent any low-frequency issues, ensuring the integrity of the compression effect across the full frequency spectrum.
Next, we move to the FET model, which is inspired by a very famous boutique compressor from the late 60s. Unlike the VCA model, the FET model operates in a completely different manner. It is a feedback compressor, meaning that the sidechain signal is derived after the gain reduction stage, which makes it inherently non-linear. The result is a more program-dependent compression characteristic, which is a key factor in shaping the signature sound of this compressor.
In a feedback compressor, the sidechain signal is affected by the gain reduction, leading to a compression curve that becomes more drastic as the input signal increases. In practical terms, this means that after crossing the threshold, the compression starts to intensify, and as the signal level rises, the compression ratio increases too. This leads to a harder knee when using higher ratios, which is characteristic of the FET’s aggressive behavior.
The analog emulation of the FET model also activates a waveshaper. This waveshaper is designed to simulate the saturation effect produced by class A amplifiers, further coloring the sound of the compression. Additionally, the model features a DC blocking stage, ensuring that low frequencies remain intact, providing a clean and tight compression effect on your tracks.
The third model is the OPTO model, which is inspired by a classic vintage compressor that uses an electroluminescent panel as its core mechanism. This model offers a more gentle and musical approach to compression, making it a favorite for many engineers who appreciate its natural, smooth behavior. One of the most unique aspects of the OPTO model is its frequency-dependent response. It tends to compress low-end frequencies more aggressively, which helps to tighten up bass-heavy elements like kick drums and bass guitars.
In addition to its frequency dependence, the OPTO model also features a strange release time. When the gain reduction starts, the release happens fairly quickly. However, once the signal drops to around 50% of the luminescence, the release time extends significantly, sometimes lasting up to ten times longer than the initial phase. This gives the OPTO model a two-stage envelope detection characteristic, which leads to a distinctive pumping effect on the compression, making it ideal for dance music and more rhythmic genres.
As with the other models, the analog emulation of the OPTO model engages a waveshaper that simulates the saturation of a class A amplifier. The DC blocking stage ensures that there are no low-frequency issues, maintaining the quality and clarity of your mix.
Now that we’ve explored the individual models, let’s take a moment to compare them. The VCA model is ideal for users who require precise, transparent compression, making it a versatile choice for various genres, including pop, rock, and electronic music. It is clean, efficient, and great at controlling dynamic range without adding noticeable color.
The FET model, on the other hand, is more suited for those who want a dynamic, punchy sound with a more aggressive edge. It excels at delivering more character and warmth, especially when applied to vocals, drums, and any material that needs that “vintage” feel. It’s perfect for genres like rock, indie, and even some electronic styles that require a bit more bite.
Lastly, the OPTO model offers the smoothest and most musical compression, making it perfect for vintage applications. Its pumping behavior makes it an excellent choice for rhythmic elements or adding an organic, flowing feel to the mix. It’s ideal for genres like classical, jazz, or acoustic music, where natural sound shaping is paramount.
All three models include analog emulation to enhance their inherent sounds. Whether it’s the VCA, FET, or OPTO model, when you engage the analog emulation feature, you’re adding a layer of warmth and saturation that can only be achieved with analog circuitry. These nuances add character to your sound, allowing you to bring more life to otherwise sterile digital mixes.
In summary, each of the three compression models—VCA, FET, and OPTO—offers a unique approach to dynamic processing. Whether you’re looking for precise control, aggressive punch, or smooth, vintage warmth, there is a model to suit your needs. The addition of analog emulation further enhances the character of these models, giving you the flexibility to choose the right sound for any project. Understanding the differences between these models can help you make better creative decisions and elevate your mixes to the next level. If you have any more questions or need further clarification on any of the points mentioned, feel free to reach out, and I will be happy to assist you!
