In today’s pristine digital audio world, artists, engineers, and producers are often seeking the unique sound of analog saturation for the soft compression, harmonics, and distortion that can provide a variety of benefits. Analog saturation is highly coveted in modern production, often associated with words like “warm,” “round,” and “sounds like a record.”
For many of us, saturation sounds familiar due to its almost unavoidable presence in so much of our favorite music. Classic recordings often had saturation baked into the music at varying stages before digital audio and modern equipment offered more ways to avoid saturation. It’s common for today’s musicians and engineers to degrade perfectly clean digital audio with saturation, adding harmonics and imperfections that many interpret as more pleasing by comparison.
Saturation is a broad term that ranges from subtle warmth to wild distortion. Let’s review what saturation is and where it occurs in the hardware most commonly used in mixing and mastering.
Saturation occurs when electrical components inside a piece of hardware are overloaded. This means a signal’s input can no longer be matched to the output in a 1:1 linear fashion. As the input exceeds the capacity of the components, a soft knee compression of the audio occurs, and in some instances, harmonics are generated and added to the audio. This reduces amplitude in the loudest parts of the signal, bringing the quiet parts closer in amplitude to the now reduced loudest parts. It’s almost exactly like using a compressor with a soft knee.
Harmonics are generated by specific electrical components in unique ways. Even order harmonics follow a sequence of 2,4,6,8 etc., and are multiplications of the root frequency. Odd order harmonics are sequences of 3,5,7,9 etc. Even order frequencies occur in the intervals of octaves and 5ths, while odd order frequencies are made of thirds.
Even-order harmonics are often described as subtle and round compared to odd harmonics that bring more of an aggressive edge to the sound. Many electrical components produce both, but one type of harmonic is more present.
For example, as a tube is overwhelmed by the incoming signal, even order harmonics are generated and most audible, though some third-order harmonics are also added. Even harmonics from tube saturation are typically closer to the fundamental frequency and lower in the frequency spectrum, which is often perceived as warm and thicker sounding.
Tube saturation can be explored in our Manley Vari Mu Stereo compressor, SPL Vitalizer, LA2A, Pultec EQP1-A, Highland Dynamics BG2, etc
Since transistors are common in audio equipment, they are the most frequently encountered source of saturation. Transistor saturation occurs when the input current causes the voltage to drop, which then prohibits any additional electrical signal from being added. Transistor saturation adds both even and odd-order harmonics, the amount of each depends on the specific components behavior. Transistors can be found in consoles, guitar pedals, compressors, etc.
Another source of color can be saturation from pushing a transformer. Simply put, transformers isolate two circuits and control the voltage, current, and impedance. Iron, nickel, and steel cores can be utilized in transformers, and each imparts a unique sonic signature. Small nickel transformers have less color vs. larger steel core or the even more colorful large vintage iron cores.
As louder signals are applied to a transformer, more low-frequency harmonics are generated than high-frequency harmonics, adding density to the signal with results that most consider warm. It is common for several transformers to be in a signal path – sometimes on both the input and output of a single device, or unique transformers in each device in the chain such as preamp, compressor, console, etc.
The Black Box HG2 offers transformer saturation that can be applied to the entire frequency spectrum, just the low frequencies or, alternatively, just the high frequencies. This is a great way to explore transformer color since it can easily be bypassed for A/B comparisons. The HG2 also offers three tube types that can be driven for a variety of tones. The Highland Dynamics BG2 compressor has several color options via the 150/600ohm switch and the British/American modes – a great way to explore tubes and transformers together.
The Rupert Neve Designs Master Bus Processor can be a great place to explore even and odd order harmonics due to the Silk circuit – Silk Red adds odd order harmonics while Silk Blue emphasizes even order harmonics.
It is important to recognize that saturation requires careful attention to gain staging, since saturation is achieved by stressing audio components until they behave in a non-linear fashion. By comparison to a digital signal, analog audio has more headroom to push your audio volume. Digital audio clipping results when the signal exceeds 0db and is not often a desired sound.
Analog hardware begins to compress the signal and shave off loud transients as you reach the limits of the hardware capacity – this is precisely where the pleasing saturation we are looking for occurs. Pay careful attention to the gain on the hardware controls. Utilize the gain adjustment inside the Analog Matrix plugin to manage how much signal is going into each device and how much signal is returning from the device to the Analog to Digital conversion. These can be adjusted separately L/R or in stereo to easily make balancing gain adjustments.
Analog saturation is a powerful tool for producers, engineers, and artists seeking to add warmth, character, and depth to their digital mixes. As we have seen, saturation occurs when electrical components are overloaded, resulting in soft compression and the generation of harmonics that can range from subtle to wild. Tubes, transistors, and transformers are the most common sources of color, each with its own unique sonic signature.
By exploring the various types of saturation and experimenting with different devices, it’s possible to add a level of richness and complexity to your music that is often hard to achieve with digital processes alone.
In our upcoming blog posts, we will expand on each type of saturation with some suggested devices for each and some tips and tricks for specific applications.
