Gain Structure | FOH Masterclass ft Robert Scovill | Hillsong Creative Audio Training

Summary

The speaker emphasizes the critical role of gain structure in digital audio, particularly in live sound engineering. They argue for a single optimal method to set input gain on digital consoles to ensure the console operates at its best. Explaining the non-linearity of faders and the importance of high-resolution mixing, the speaker details why setting input gain correctly is essential for maintaining bit resolution and avoiding noise. They contrast live sound with studio recording, highlighting the unique challenges of live mixing and the impact of input gain on fader levels, dynamics processing, and recording levels. The talk concludes with advice on using audio subgroups effectively to balance levels without sacrificing audio quality.

Takeaways

• 🔊 Gain structure is critical in digital audio to ensure optimal console operation and prevent distortion.
• 🎛️ Setting input gain correctly is fundamental; it simplifies subsequent mixing and mastering processes.
• ⚖️ Faders in a console are not linear; moving a fader represents a logarithmic, not linear, change in volume.
• 📈 The position of faders is crucial for high-resolution mixing, aiming to keep them in the upper range for better control.
• 🎚️ Input gain on a digital console should be set to achieve a level around zero dB, aligning with line level standards.
• 📊 Different console scales like dBu, dBr, and dbFS represent the same signal level but in different ways.
• 💾 In live sound, a 24-bit depth preamp translates to approximately 6 dB per bit, maximizing bit resolution for clarity.
• 🔉 High input levels in live sound can indicate the need for a more powerful PA system rather than adjusting console levels.
• 🔕 Turning down the preamp to manage loud signals can result in lower bit rates and reduced resolution, affecting sound quality.
• 🔄 Using audio subgroups (sub masters) instead of VCAs preserves gain potential for aux buses and maintains optimized levels for effects processing.

Q & A

Why is gain structure important in digital audio?

Gain structure is crucial in digital audio because it ensures the console operates in an optimized way. If the gain is not set correctly, it can lead to poor sound quality and loss of resolution, which is especially problematic in digital audio where there is no room for forgiveness as there might be in analog.

What is the recommended way to set input gain on a digital console?

The recommended way to set input gain on a digital console is to adjust the preamp until the signal reaches zero on the line level, which translates to around +4 dBu in analog terms. This ensures high-resolution mixing and optimal operation of the console.

Why is it not advisable to skip setting input gain correctly?

Skipping the correct setting of input gain can lead to a signal that is either too high or too low. A signal that is too high can clip, leading to distortion, while a signal that is too low can result in noise and a loss of bit resolution, negatively impacting the overall sound quality.

How does the position of a fader affect the change in volume?

The position of a fader on a console is not linear but logarithmic. This means that moving the fader a certain distance at a higher level results in a larger change in volume than the same distance at a lower level. It's important to have faders in a high-resolution position, typically around zero, for optimal mixing.

What is the purpose of a preamp in a sound console?

A preamp is used to amplify a mic level signal up to line level. This is necessary because all consoles are optimized to work at line level, not mic level. The preamp ensures the signal is strong enough to be processed effectively through the console.

What is the significance of the line level in a console?

Line level in a console is a reference point that indicates where the signal should be for optimal performance. In the context of the script, line level is represented by zero on the console's meter, which corresponds to +4 dBu in analog, ensuring the console is set up for high-resolution mixing.

How does the bit depth of a digital signal affect the noise level?

In digital audio, bit depth determines the dynamic range and the signal-to-noise ratio. A higher bit depth, such as 24-bit, provides a greater dynamic range and better signal-to-noise ratio, meaning the noise is less likely to compete with the main signal. This is important for maintaining audio quality.

What is the relationship between input gain and fader levels in live sound?

In live sound, the input gain directly affects the fader levels. If the input gain is set correctly, the fader can be positioned for high-resolution mixing. If the input gain is too high or too low, it can force the fader levels to be adjusted in a way that compromises the audio quality or the dynamic range of the mix.

Why is it important to set the input gain to maximize the bit resolution for live sound?

Maximizing bit resolution in live sound ensures that the main signal is represented with the highest possible clarity and detail. This is important because live sound engineers often have to manage a variety of signals with different levels, and maximizing bit resolution helps to maintain audio quality across the board.

What is the difference between using a VCA subgroup and an audio subgroup in live sound?

A VCA subgroup adjusts the gain of all channels in the subgroup uniformly, which can reduce the bit resolution and affect the dynamics processing and aux levels. An audio subgroup, on the other hand, allows for independent level control of the subgroup without affecting the individual channel gains, maintaining optimal levels for recording and processing.