Gain vs Trim. Don't Reach for the Wrong One!

“What is the difference between Gain and Trim?” I hear this question often. There are advantages to both, but there are also a few things that can cause issues if used incorrectly.

Preamp Gain is Setting the Foundation for Your Mix

Preamp Gain is the initial stage of amplification for the incoming audio signal from your microphones or instruments. Setting this gain correctly is vital for several reasons:

Achieving Nominal Gain

Nominal gain is the optimal input level setting, typically around -18 dBFS, that ensures a strong, clean signal above the noise floor without clipping. This setting also ensures that all 32 channels on your console when mixed together average a full, non clipping, output on the stereo buss.

Eliminates Noisy Channels

This level also ensures that the signal is strong enough to be well above the noise floor, providing a clean and clear sound. This is called the signal-to-noise ratio. Having a high signal-to-noise ratio will help your mix!

Preventing Clipping and Distortion

If the preamp gain is set too high, the signal can clip, resulting in unwanted distortion. Clipping occurs when the signal exceeds the console's maximum level, causing it to be truncated.

Digital Trim: Fine-Tuning the Signal

Digital Trim is useful for making fine adjustments to the signal level once the preamp gain is set. It allows for small level adjustments to ensure that each channel sits well in the overall mix.

Preamp gain is used to amplify the input signal to an optimal level for clean sound, while digital trim is used for fine-tuning that signal without altering the fundamental gain structure.

Limitations of Digital Trim:

Digital Trim cannot correct issues caused by incorrect preamp gain settings. If the preamp gain is set too low, increasing the digital trim will also raise the noise floor, resulting in a noisy signal.

Similarly, if the preamp gain is too high and the signal is clipping, reducing the digital trim won't fix the distortion. Once the signal is clipped, the distorted signal is already recorded, and no amount of digital adjustment can restore the lost information.

Practical Example

Multiple Consoles on the Same Digital Stage Box

When multiple consoles are using the same stage box, one console typically becomes the primary where preamp gain and phantom power is controlled from. The remaining consoles then have the ability to trim this preamp level up or down to suit their needs for their console.

One prime example of this is having a broadcast console along with a FOH console. The broadcast console sometimes needs different gains (sometimes hotter) for the channels than the front of house console. As long as the primary console doesn’t clip the preamps, using trim is a perfect use for this.

Proper Gain Staging

Proper gain staging, starting with the preamp gain, is essential for achieving high-quality sound. Here are some key points to remember:

• Start with Preamp Gain:

  Always set the preamp gain first to achieve a nominal level of around -18dBFS. This ensures a strong, clean signal with ample headroom.

• Use Digital Trim for Fine Adjustments:

  Once the preamp gain is set, use digital trim to make minor level adjustments as needed.

• Monitor for Clipping and Noise:

  Keep an eye (and ear) on your levels to ensure there is no clipping or excessive noise. Adjust preamp gain and digital trim accordingly to maintain a balanced, clean mix.

By understanding and correctly setting Preamp Gain and Digital Trim, you can ensure that your audio console delivers the best possible sound, free from noise and distortion.

Until next time,

Drew

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