Basic Electronics for Recording Engineers - Part 4 - Gain Staging

The design of professional recording gear requires knowledge of how to best distribute the necessary gain through multiple internal gain stages. In this episode, I explain how that is done, and how you can use the same principles to achieve the best gain-staging of all your equipment. Proper gain-staging optimizes the signal chain for lowest noise, and the least distortion.

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Transcript

116        Basic Electronics for Recording Engineers – 4 -- Gain Staging          April 23, 2026

I’m Doug Fearn and this is My Take on Music Recording

 When I first learned something about how airplanes were designed, I realized how some of the same principles were analogous to the world of recording. In fact, I found similar analogs in almost every technological area I learned about, such as radio, chemistry, and photography. The laws of nature are remarkably universal.

Before the advent of computer-aided design of aircraft, the process was largely empirical. You tried something to see what would happen, determined what was good and bad about your design, and then made changes to the design to make it work better.

At some point in the development of the studio gear I design, the empirical approach is part of my process.

Let’s take an aeronautical engineer in the 1950s who is tasked with designing an airplane wing. One fundamental thing about airplanes is that they have to be as lightweight as possible, while still being strong enough not to fail in extreme conditions. An airplane can only safely transport a certain amount of weight. Any more weight reduces the safety factor of the design. And anything that is heavier than necessary reduces the payload an airplane can transport.

So what designers did back then was to use their best judgement and experience to draw a proposed wing, according to the demands placed upon that wing for lifting capacity and protection from failure.

They would build a prototype wing, and then test it by loading it up until it failed. They did that using sandbags placed on the wing, one at a time, until something in the wing structure broke.

Then they would examine what failed and what stayed intact. They strengthened the broken part, and perhaps reduced the strength of the parts that survived. The goal was to reach the design load, plus a generous safety margin.

They did this over and over until they reached a point where the last bag of sand applied caused every part of the wing to fail. They now had a wing that was as strong as it needed to be and also as lightweight as it could possibly be.

The actual process was more complex than my simple explanation. They had to consider many other factors in addition to how much weight the wing could endure. But this example will help us understand audio equipment design, and gain-staging in the studio.

This is part 4 of a series on basic electronics for music recording engineers. In part 3, I talked about equalizers and amplifiers in a very general way. In this episode, I discuss what goes into good amplifier design. And by “amplifier” I am referring to any generic gain stage, which is fundamental to all our audio gear.

To illustrate this, I’ll use an example of a microphone with an output of around -50dBm. We want to be able to listen to the microphone on our monitor speakers. We determined that we need an overall gain of about 90dB, to provide about 10 watts to our speaker.

How we distribute that gain across all the internal amplifier stages in the equipment is a task for the design engineer. But we can use the same principles in our own daily studio challenge of what has been called “gain staging.” The term comes from the electronic engineering world, but it is a useful concept for practical setup of our recording chain.

The goal of proper gain staging is to maximize headroom and minimize noise. Those are two conflicting requirements, so a best middle-ground is the goal.

Let’s say we have four amplifier sections in a piece of studio gear, in this example, a microphone preamplifier. The conflicting design goals require a certain amount of gain, along with a minimal amount of added noise, all while keeping the distortion as low as possible.

The difference in level between an average level and the point where distortion exceeds an acceptable threshold is called headroom. In analog studio gear, usually at least 20dB of headroom is a design goal. If the equipment is designed for standard studio line level of +4dBm, that means that the equipment should be able to handle a +24dBm input level without unacceptable distortion. Things are different in the digital world, where, by definition, the absolute maximum level is always 0dB full scale.

You could design each stage independently, with the one-quarter of the required gain, and see what happens. If you need 60dB of overall gain, that would be 15dB of gain for each stage.

But a better approach is to look at each amplifier stage as one “gain block,” with the optimum amount of gain contribution. The goal then becomes to determine which of these stages “fails” first. For example, if the lowest possible distortion is the goal, which stage first goes into unacceptable distortion as you increase the input level?

You could do this by ear, but in the early part of a design, it is faster to use test equipment to monitor the output of each individual gain stage, looking for the first one to distort.

We then modify that stage to be more robust, if that is possible. That might mean decreasing the gain of one stage and increasing the gain of another stage, always maintaining the desired overall gain for that piece of gear.

Once we fix that first worst-stage distortion, we then see which next stage fails the distortion test. And so on. The goal might be to have all the stages go into distortion precisely at the same input level. It’s like the airplane wing.

That may mean that each stage has a different amount of gain, rather than an even distribution.

Of course, distortion is not the only criterion we need to consider. Other things change as we modify our gain stages. What is the nature of the distortion that results? Which stage adds the most noise? Are there other things that change, like the phase response? Is the frequency response still as flat as possible?

In the recording studio, you don’t have to worry too much about these criteria, because, presumably, the design engineer has already optimized those things.

But real-world recording often has lots of different parts in the chain from microphone to speaker. There will be a mic preamp, perhaps a compressor, equalizer, or other sound-modifying device in the chain. In a console, there can be several points where we can adjust gain. The converter has its own design factors that affect the sound, depending on the level it receives. The speaker system, active or passive, has amplifiers, too. We can adjust the gain at many of those points. And how we do that affects what is going to overload first.

We are just talking about level here, but noise is closely related to amplifier gain. Let’s say you set your mic preamp so it has a low output – well below its optimum output level. You then compensate for that low level by increasing the gain at some other point farther along the audio path, such as a compressor, or in the console or DAW. That’s not likely to be the optimum gain distribution, however.

What is the best setting for each stage of amplification?

I can’t give you a definitive answer because your equipment is probably at least somewhat unique to your studio. Some of this fine-tuning of gain-staging will have to be determined empirically. That is, you have to experiment and see what happens.

But there is one general rule that I think is a good starting point: always apply the most gain at the earliest point in the chain. In other words, the mic preamp should provide the most clean-gain possible.

Most mic preamps have some sort of level control. On a console, there may be adjustable gain for the input to the mic preamp, such is in classic Neve consoles, where intricate switching of various components of the mic preamp can be adjusted in fixed steps. Other consoles may have a preamp gain control. Remember the trade-off between gain and distortion and noise? You need to find the preamp gain that optimizes all three of those.

You could get a sense of that with test equipment, if you had it available and knew how to use it. But music is not a simple sine wave tone. The dynamics of musical instruments means that we need to consider the peak levels, not just the average level. I talked about that in the episode called, “Microphone Preamplifiers: how I designed the D.W. Fearn preamps and how you can get the most out of them” from August 2020.

Simplified, real world sounds can have a peak level that is 20dB or more above the average level. Those are usually in the form of transient peaks, typically at the very start of the note. Some instruments, like an oboe for example, might have an initial peak at the start of the note that is only a few dB above the level of the sustained note. But other instruments, like a piano or drum, could have initial transients that are much, much higher than the sustained note. The average level of a piano might be only tens of millivolts out of the mic, but the percussive hit of the hammer on the string can produce a peak that is well over 1 volt! That transient helps define the sound of a piano, or a snare drum, and if that peak goes into distortion in the mic preamp, the sound loses its impact. It no longer sounds real. You can get away with that sometimes, but in general, that overload on the peaks makes the music less impactful.

You need at least 20dB of headroom to preserve the true sound of many instruments.

Most gear has the most distortion at the low end of the audio spectrum. That worst-case distortion at, say, 20Hz, will be the determining factor for headroom optimization.

Although most distortion comes from the active devices in a circuit, some passive devices, like transformers, can also introduce distortion when overloaded with excessive level. Some people like the sound of transformer overload, which is caused by saturation of the transformer core. That point is reached when the applied audio level exceeds the amount of magnetization the transformer’s iron core can handle. If that is a creative choice, go ahead and use it. I agree it can sometimes be just the sound you need.

But mostly transformer saturation is not what you want to hear. How do we prevent that?

Every instrument has a typical sound pressure level. Every mic provides a slightly different output level on any instrument. The range of mic output levels could vary by more than 60dB in extreme cases, from a distant-mic’d quiet sound while using a ribbon mic, to a condenser mic placed very close to a very loud sound.

Most mic preamps have a built-in pad that can be switched in to reduce the input signal level by about 20dB. That will almost always prevent the input transformer from becoming saturated. But you have to use your ears to decide if that is what you want. A pad is a network of resistors that attenuate the signal level. A microphone working into a pure resistance may have different audible characteristics from when it is operating into a transformer. A transformer introduces some inductive load, as well as resistive, and we know that inductors can affect frequency response, and a different load on the mic can affect several of its characteristics. So a preamp pad may change the sonic character of the mic. You need to make a creative decision. It’s a trade-off. Usually a pad provides more benefit than detriment, but not always, and it will differ between various microphone and preamp designs.

Many modern mic preamps are designed so that they do not need an input transformer. Switching a pad in and out may not change the sound very much, compared to a preamp with an input transformer. Instead, a tranformerless mic preamp may go directly into amplifier-stage overload. That will sound different from transformer saturation. A pad can clean up the distortion.

Condenser mics close to a very loud sound sometimes produce enough level to overload the internal electronics in the mic. Many mics have their own pad that can be used to reduce the level. The goal is to prevent overloading the mic electronics. But it has the side-benefit of reducing the level into the mic preamp.

However, to provide the best reproduction of the sound coming from the mic, while keeping the noise and distortion at their lowest possible levels, you need to determine if any overload you are hearing is coming from the mic electronics, or from your mic preamp. If you familiarize yourself with the two distinct sounds, you can often determine whether to use the mic pad or the preamp pad, just by ear. And sometimes, on extreme levels, it may be necessary to use both pads.

This is an example of how understanding how the electronics work can aid you in achieving your sonic goals.

Most outboard mic preamps have a level adjustment of some sort. It is usually labeled “Gain.” That sets the overall gain of the preamp. It is used with the input pad to make sure every part of the mic preamp is operating at its optimum level point. Some preamps also have an “output” level control. If you have access to the circuit diagram of the mic preamp, and know where to look in the circuit, you can get a sense of what the various level-adjusting controls are actually doing. Or the instruction manual for the mic preamp may give you guidance on this, helping you to determine if it is best to use the pad, reduce the gain, or use the output level control to get what you want.

You could use test gear to get an idea, but mostly you have to use your ears. What you hear, coupled with what you know, will help you get the sound you want.

Fortunately, well-designed mic preamps have a fairly wide range of levels where they sound good, so you can often get away with less-than-ideal gain staging in the mic preamp. But if you can improve the sound by even a few percent, why not? If you can find several of those improvements, how much better might the final product sound?

That’s an example in just one part of our recording chain. Apply that knowledge to all the amplification stages in the chain and you can optimize each.

For another example, I find that every console, and every DAW, has an optimum bus level. If your faders are all up too high, the sound suddenly starts to lose something, even if the output bus meters are showing a reasonable level. This is something you will have to determine by experience. Let your ears guide you. Use the various level indications as a general guide, but adjust the gain at every stage for the kind of sound you want. It is amazing how just dropping every fader a few dB can suddenly bring a mix to life.

When using an equalizer, remember that all the boost you are adding at various frequencies is adding to the output level of the equalizer. Some outboard equalizers have a control to adjust the overall level of the equalizer. You can use that control to optimize the level into the next device. Too much boost may overload the next stage in your chain. Find what sounds best.

Compressors usually have a make-up gain control. Compression always reduces the level, and the makeup gain is set to restore the proper output level of the compressor. Many plugin compressors can automatically adjust the makeup gain. The output level is changed to approximate the amount of compression applied. It makes things simpler, and helps maintain the best gain structure.

But on a hardware compressor, you are going to have to do this makeup gain adjustment yourself. The compressor may have a way to meter the output level, which can help. But again, use your ears to make sure you are not overloading the next stage in the chain, which could be the console input, a converter input, or another piece of outboard gear.

When the gain structure is way off, you will probably hear it as either obvious distortion, or as excessive noise, depending on whether the level at any stage is too high or too low. The trick is to detect the problem before it becomes blatantly obvious, and correct it at the proper point.

For example, say your mic preamp gain is set too low. The output should be around +4dBm, but you set the gain too low and the actual output is around -6. That’s 10dB lower than optimum. “No problem,” you say, “I’ll just increase the threshold on the compressor.” You patch the compressor into the chain, after the mic preamp. Now you get the proper level into your converter, or console. But by making the compressor add an additional 10dB of gain, you will also increase the noise level by about 10dB. Is that acceptable? Maybe it is not an issue in the music you are recording. But it could be.

It might be an even bigger problem if you later decide you need more compression on the vocal. Or in the mix, you might change the arrangement by dropping out many instruments, leaving mostly the noisy vocal track up. Can you hear the noise now?

This a common trap when you notice something is not right and reach for the wrong control to reduce, or increase, the gain. Blindly adjusting something is not the formula for the best sound. Analyze where the gain is improper and correct it there.

In our example, fixing the mic preamp gain will require a change in the compressor settings. Otherwise, the amount of compression is going to go up by 10dB, which is unlikely to give you the sound you want. In a busy session, do you have time to make all those level changes? Maybe not. But it is far better to get it right from the start so you won’t have to deal with a noise or distortion problem later. 

A similar problem occurs when the mic preamp gain is set too high. You compensate by changing the compressor settings. The result is likely much more distortion than you would have liked. You now know how to analyze this problem and find a way to correct it while tracking.

Ask any mix engineer and they will probably tell you that they spend a lot of their time trying to fix the problems of improper gain staging created by the tracking engineer, especially on vocals.

Some engineers have lived with suboptimal gain structure for so long that they are no longer hearing the problem. They may think that this is their signature sound. And I won’t argue with that, if you are making successful records. Recording quality is entirely subjective, and we all have a sound in our head that appeals to us. We should strive for that sound.

But knowing that there are simple techniques available to you to modify that sound will allow you to find your sonic nirvana. Use your knowledge to craft your unique sound.

I have used an analog signal path in these examples, but it also applies to audio in the digital realm. The problems may manifest as a different kind of noise or distortion, but the same principles of gain staging apply. After all, most of our digital audio devices are simply a digital version of analog devices.

Next time I will talk about how to interpret a schematic diagram. This knowledge can be helpful in troubleshooting a piece of equipment, or just to gain a better understanding of how the equipment works. And understanding how it works internally may give you an extra tool to use when you are trying to achieve the sound you want.

Thanks for listening, commenting, and subscribing.

You can reach me at dwfearn@dwfearn.com

 This is My Take on Music Recording. I’m Doug Fearn. See you next time.