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Understanding Bypass and Mix controls on plugins

Before delving into the bypass behavior, I'd like to emphasize and include this disclaimer:

I genuinely appreciate the mentioned plugins used in these examples. Understanding how the tools in our arsenal work will aid us in making better decisions in our mixes. Discovering "artifacts" and differences between bypass methods DOES NOT IMPLY THAT THE PLUGIN IS INFERIOR. It simply suggests that you may want to consider it in certain setups. This article aims to leave you more informed and knowledgeable about bypass behavior.

Now, let's distinguish between Bypass and In/Out controls, as they are not the same. In DAWs like Cubase or StudioOne, you'll find two separate controls for bypass/in-out.

Bypass will keep the plugins on, meaning CPU and memory consumption, and latency should remain the same. The signal still goes through the plugin but in an alternative signal path that SHOULD be as clean as possible.

In/Out will disable the plugin, its latency, and remove it from CPU and Memory.

For example, Logic has a single button called "bypass," but it takes the plugin off the CPU. It's crucial to understand how your DAW's bypass mechanism works, as not all bypass controls are created equal.

Now that we've established that the Bypass we're referring to does not disable the plugin but provides an alternative signal path within the plugins, let's discuss "unclean" bypass.

When I say "clean," I mean that the input signal equals the output signal, i.e., the original signal will cancel out compared to the same signal going through the plugin in bypass. In this scenario, the signal still inherits the latency of the plugin, so it's important to ensure that delay compensation is enabled.

"Unclean" bypass can be intentional and, in most cases, not a bug. It can be related to various attributes and qualities of the plugin itself, such as crossover, internal oversampling, or internal bit depth manipulation (floating point).

Bypassing plugins with a built-in crossover may result in a loud click/pop sound, which, aside from being annoying, can harm your speakers in some setups or be a big issue in a live gig context.

To address this, manufacturers have chosen to split the signal for the bypass after the crossover to prevent these issues and protect users.

It's easy to take for granted the advanced tools we use today and simplify our understanding to emotions and "vibe," but underneath, many smart and talented engineers are solving problems we may not even be aware of.

Different companies and engineers have solved these issues during development in various ways. For example, in the Classic Multiband Limiter by T-rex (IK Multimedia), you can observe that the plugin does not cancel versus the original unprocessed signal.

What does this mean for you in your day-to-day workflow?

I would recommend using this plugin on your buses/Auxes.

You can certainly use it on individual tracks as well.

However, if you have parallel tracks of the same signal or if you insert this plugin on material recorded with multiple microphones, I recommend checking the phase relations between the different tracks to see if the crossover phase shift is working for or against you.

In this example, we can explore another favorite of mine, the Grindstein plugin.

We can observe that activating the HD function before bypassing the plugin will prevent the plugin from canceling out against the original signal, as expected. This is because the bypass signal path still traverses the Upsampling/Downsampling modules of the plugin. In contrast, other plugins, such as Neural DSP DarkGlass, have a clean bypass.

Please keep in mind that some manufacturers will internally upsample the signal by default.

As discussed in a previous article, oversampling allows you to process the signal at a higher resolution. However, the sonic improvement may not always justify the additional latency and CPU consumption.

Moving on to the topic of bypass, another item I'd like to address today is MIX knobs and their placement in the signal flow.

The design of MIX knobs may vary among different manufacturers and is based on the plugin, process, or workflow they present to us.

Some questions to consider are:

Is the mix post-output gain or pre-output gain?

For example, if setting the mix between my processed signal and the "clean" signal renders the plugin's output gain useless, or if the output gain controls the overall level of the dry and wet signals.

I can assure you that your answer will vary based on the context. For instance, a bass player accustomed to the SenseAmp Blend & Level controls may have a different perspective than someone who is familiar with working with reverb plugins. Much like anything else, the developer needs to find what works best for the community they are developing for and what will serve the product's signal flow.

Therefore, you may encounter various types of mix knobs. As long as you take the time to understand the signal path and what "dry" actually means, you will be fine.

Here are a few examples:

H-Comp's Output knob affects the "dry" signal path as well.

JST JW BG Guitars Mix is post-processed; I assume it is related to a built-in crossover, as it behaves the same when bypassed.

While the Purple Audio CM77 by PA Mix is pre-output, i.e., the output gain will only affect the "wet" signal.

So, to sum it all up!

All these products are amazing. The fact that they do not operate in the same way does not mean that one product is better or worse than the others. There are no strict rules, but it's essential to understand how your plugins function, enabling you to make more educated decisions and be aware of what to look for when auditioning various tools for your mixes.

With that being said, I hope that this new knowledge empowers you to make better mix decisions, allowing you to create amazing music and well-mixed tracks.

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