If you have ever used a guitar amplifier or a mixing console, you have most likely come across controls called gain and volume.
These controls have been found on music gear for a very long time yet there is still great confusion around them.
Knowing what they do and how they differ can make a huge improvement to your overall sound!
Have you ever found yourself wondering what those gain controls really do exactly? Let’s dig in and find out how gain and volume differ!
What Is Gain?
The use of the term gain in audio is a derivative from the term “voltage gain” used in electronics. The difference in magnitude between the output signal and the input signal of an amplifier is called gain, and is normally measured in decibels (dB).
Another way to look at gain, is to consider the benefit you would receive if you bought something for cheap, and then sold it for more.
Let’s say I bought a Fender Deluxe Stratocaster for 500 bucks, but then sold it for 800. I would have made a gain of 300 bucks.
Gain in audio is the same type of thing, you put a signal on the input and you get a larger signal at the output.
But not all equipment is created equal! And so you have to ask yourself, what is it that im putting a signal into and what am i expecting from it? Let’s look at a few examples.
Gain On An Instrument Amplifier
The preamp is needed to amplify an input signal that is too low in order to use it for processing or control.
A guitar puts out a very small signal that cannot be used unless it is increased in magnitude by a preamp.
The gain control on an amplifier lives in the preamp section and dictates how much of an amplified signal is allowed to proceed into circuits following the gain control.
In the preamp of most amplifiers you will find that there are many active gain stages (tube or solid state normally) all connected together or cascaded in series.
One gain stage boosts or amplifies the signal and passes it on to the next.
As the signal keeps growing it tends to start becoming too large for the following stages to handle and they begin to start distorting the signal.
The gain of each stage simply begins to become too much and the stages produce the guitar distortion we know and love today.
The Gain Control Is Born
At some point in the early days of guitar amplifiers, designers decided to put a gain control between the first couple of gain stages to let players alter how much the gain stages could distort.
This allowed players to forge their own sound by limiting how much gain the preamp was allowed to produce among the stages.
Your gain control also controls how much signal the preamp will send out to the power amplifier.
The higher the setting the hotter the signal which is why it’s easy to assume it is a volume control.
The gain control on an instrument amplifier is primarily there to control how much distortion and tone shaping you want in your guitar sound.
So think of the preamp section as the area of the amp where the tone shaping is done. This is home to the gain knob on a guitar amplifier.
Gain On A Mixer
The gain control (also known as “trim”) on an analog mixer regulates the amount of input signal it receives from the device plugged into it.
Because many devices like microphones and instruments can be used on a mixer, the signals from these devices can be drastically different.
The gain control is used to limit how much of the signal is allowed to proceed into the channel circuit.
The main objective of the gain control is to allow the strongest input signal possible for optimal sound while preventing any distortion or clipping of the channel circuit.
Many people mistakenly refer to this control as a volume control which is why this confusion exists in the first place.
The volume of the channel is controlled elsewhere while the gain control keeps the sound quality in check by preventing distortion.
Too much or too little input signal will ruin sound quality in a hurry!
Its very easy to assume gain is volume because any extra input signal will increase volume slightly at the other end as a result of turning the gain up!
Look at it this way, If you were to sing into a microphone during sound check and set your gain to the threshold of clipping for a nice strong signal, you know for a fact that once you start performing and adrenaline starts to flow, you will sing louder!
That channel is going to clip like crazy and distort the vocals for sure once you do.
You can adjust your volume control all you want and that channel is still going to clip.
But once you turn your gain control down, the channel no longer clips. So what’s going on there?
The input signal got stronger when you began to sing louder which then produced more gain.
This extra gain then overpowered the rest of the channel circuit and clipped the signal.
This had nothing to do with volume, because in most cases the volume didn’t increase a ton, but the channel sure got hit hard with a lot of signal gain!
What is Volume?
Volume in audio, is the perception of loudness from a sound. In this case, it is the intensity of sound waves produced by a speaker when powered by an amplifier.
The more powerful the amplifier, the louder the sound which in turn means a higher volume.
A majority of instrument amplifiers have built in power sections that drive speakers.
Most people are quite familiar with the 100 watt Marshall guitar amplifiers that were incredibly loud!
The volume on these amplifiers is produced by the power section of the amplifier. But what is controlling these power sections making them louder or quieter?
You guessed it, a volume control.
Volume From An Amplifier
The volume control on an amplifier lives right after the preamp and right before a power amp.
Your volume control regulates how much of the signal coming from the preamp is allowed to go into the power section.
With more signal into the power section, the more volume that will be produced at the speakers.
If you remember when we looked at gain on an amplifier, the gain control also had an effect on how much output signal the preamp would provide to the rest of the circuit.
When the signal the volume control gets from the preamp goes up, the louder the volume will get slightly.
If we use the analogy of a water valve, the signal flow through the volume control is similar.
When you open the water valve and water starts to flow, you will get a nice stream of water at a decent pressure.
If all of a sudden the pressure from the water source goes up, the pressure through the valve will increase as well, no matter where it is set and so the flow will get stronger.
If the pressure from the water source goes down, the pressure through the valve will decrease as well.
The volume control reacts the same way with the signal it is provided from the preamp.
And so if the preamp signal increases because of a gain control adjustment, the volume would also increase slightly because the power section would see a small increase in signal.
And so the assumption most people make is that this increase in volume must mean the gain control is also a volume control.
Volume From A Mixer
On a mixer with many channels, you will see many faders or slider controls.
These are the controls that deal with volume from the mixers channels because they are the controls that regulate the output from the channels.
As you slide the fader up, the output level from the channel goes up.
As you increase the faders from the many channels that you might be using, this begins to mix all of the channels together where they mixed audio eventually end up at the master output faders.
These master output faders are the mixers main volume controls as they then send the mixed output to another device that will amplify the output producing volume normally from studio monitors or PA speakers.
Gain and Volume Interaction
When you break an amplifier into 2 parts, preamp and power amp, it makes it easier to understand how gain and volume interact in their respective positions in the overall circuit.
Infact, they essentially do the same thing, which is why it’s hard to grasp how gain isn’t a volume control.
The challenge for most people is the fact that they both do change the volume when adjusted and so somehow they must interact with each other to control the volume.
And this is true, they do interact with each other and they do both affect the volume.
So let’s look at how the signal flows through an amp and how the signal is transferred between the 2 sections.
We will look at different gain settings to see how the preamp responds and how the volume control reacts to different gain settings as well.
Changing the Settings
For the sake of this example, a guitar input signal of 1 volt is being used to keep things simple. An actual guitar signal is much lower however.
If you look at the input signal in the first diagram, it is a clean sine wave similar to what the guitar signal might look like depending on the frequency.
As it makes its way through the preamp, it comes to the gain control at 25% which limits how much signal makes its way through to the other gain stages.
As the signal leaves the preamp, the signal is still quite clean because of the lower gain setting but we have a decent output of 16 volts thanks to the last 2 gain stages.
We then come to the volume control also set at 25% which then sends the signal into the power amp at a much lower level then what was received from the preamp.
The power amplifier then amplifies the signal it was sent by the volume control and an output volume of 75 dB is heard by the listener through the speakers.
We see that the preamp signal was clean and because of the low gain and volume settings, there is amplification but not much distortion.
Turning Up The Gain
In this diagram, we have turned the gain up to 75% from 25%.
As you can see, the signal “IN” from the guitar is still 1 volt and is just as clean as it was in the first diagram.
With the gain control higher, we have a majority of the signal from gain stage #1 making its way to the last 2 gain stages.
This added gain hits the gain stages harder driving them into distortion.
Once the signal leaves the preamp, you can see that the signal is distorted (red square lines) and is a 40 volt output signal!
The volume control in this diagram is still set at 25% like last time which sends only 25% of the preamp signal it has received.
With a 10 volt signal, the power amp then amplifies it and the listener experiences 82 dB of volume through the speaker.
The sound from the speaker would be distortion thanks to the preamp.
So we see that an increase of gain on the preamp has created a volume increase of 7 dB. This is not a very large increase and while noticeable from the speaker, is negligible at best.
Some of the huge changes we see, is that now the preamp output is heavily distorted!
This added gain has caused both distortion and most likely frequency changes from the added gain but all from the preamp. Huge tone shaping going on here!
We also see that the preamp output has increased a lot from the first diagram, yet we really only see a small volume change.
In this case the volume control and power amp will only amplify the preamp signal without actually changing its sound.
Turning Up The Volume
In this diagram, we have left the preamp alone but cranked up the volume!
We are now at a volume level of 75% from 25% and things just got LOUD! If you notice in this diagram, the gain setting is still at 75% and the preamp output and distortion is the same.
But now the volume control is letting a majority of the preamp signal work its way to the power amplifier.
Our output volume is now at 120 dB and wow what a change in volume.
38 dB difference from the volume control just as one would probably expect to have happen when turning up the volume.
The sound would still be distorted just like the last diagram but this time it is just a lot louder.
No change in tone would have happened with the increase in volume.
Now, if we were to turn the gain control back down to 25%, the signal would become lower from the preamp.
Its a negligible change in volume but a huge tone change instead!
The sound would become cleaner because the preamp would no longer be distorting but would still be very LOUD!
Just a quick note: remember to have hearing protection for musicians when using anything this loud for long periods!
Gain And Volume Conclusion
So the main thing to take away from this blog post is that the gain control does affect the volume to a degree, but it is not a volume control by any means!
In fact, the gain control is by far one of the most important controls you will come across on audio gear.
Its main objective is to either prevent distortion while providing the strongest signal possible like on a mixer.
Or its design is to create a rather large amount of distortion with huge tone shaping like that of a guitar amplifier.
In either scenario the gain knob will need to be set correctly to get the best sound performance from your equipment no matter what it is.
So next time you tweak your gear, i hope that you look at the controls differently.
Because once you understand the difference between gain and volume, not only will your sound improve, your controls should start to make a lot more sense too!
Now go tweak an amp or something!
Got a question or something to add? Leave it below.