Preamps are an essential and integral part of any amplification. Most musicians that play bass or guitar (along with vocalists) utilize the preamp every time they perform, although they may not even be aware of it!
Preamps for guitar, bass, and vocals increase the output level from the guitar’s internal outputs and microphone to line levels that can then be run through a power amp, mixing console, or PA system and have it sound like it should, as, without the preamp, you would struggle to hear anything.
Understanding what preamps are, why they are needed and how they should be something every performer is familiar with.
In this article, we’ll look at what preamps do for guitar, bass, and vocals, as well as some interesting history on this simple but necessary technology.
Why Do We Need Preamps?
If you have ever plugged your guitar into your amp and started playing, you’ve used a preamp. This is necessary because the line level coming out of the guitar, bass, or microphone doesn’t have enough volume to power a set of earbuds!
The line level is so low that if you plug your instrument directly into a PA, you’d hardly hear it. The preamp is the tech between the instrument and the power amps/PA/Mixer that boosts the output signal to a level that can then be used and amplified to deliver the final sound.
Preamps Create Your Sound – Power Amps Finish It
Whether playing electric guitar, bass, or vocals, preamps have another very specific and unique function: to create the final sound or tone you want. Musicians, especially guitar players, work countless hours on their ‘tone.’
Now, this could be any tone depending on the song or type of music they play, and vocalists are no different. Using preamps allows performers to fine-tune their sound and store it so they can simply activate it during a performance as and when they need it.
There are almost infinite resources online where top musicians explain what pedals and settings they use to achieve their tone and sound, whether on specific songs or as a whole. Most of that sound comes from the preamp side.
Adjusting gain, distortion, delay, reverb, bass, mid, and treble are all made in the preamp stage, and while power amps also have a role in the final sound, the preamps do most of the work, and the power amps finish it off.
Suppose you look at the British Vs. American amps, the valves they use to create a different sound from the preamp line input, where the tone is finalized.
If you consider that manufacturers like Marshall and Vox would use valves like the EL 34 and EL 84 that provide a warmer, richer sound, while American amps like Fender and Mesa Boogie use cleaner sounding 6L6 and 6V6 valves.
The valve configuration will determine the final sound produced by the amplifier. Your choice of power amplifier will depend on what effect you want the preamp signal to have on it once it exits the power amp.
What Types Of Preamps Do You Get?
Preamps come in a few shapes and sizes, but the two most common ones are the internal preamps in your amplifier or preamp pedals. Yes, those footstompers you have at your feet are preamps as they boost the signal coming from the instrument (guitar/bass/microphone), which is then sent to the power amplifier.
While we will look at the differences between the preamp and power amplifier later, whether using a pedal as a preamp or the amplifier’s preamp section, your initial signal is boosted before being played through the speaker,
While you may have several pedals or a single multi-effects pedal, the function of the pedal is to boost the initial signal to line level and apply the pedal’s specific effects or bank to the signal before it gets to the power amplifier section.
With many modern pedals, especially multi-effects products, you can connect these to a computer and fine-tune settings using your mouse rather than the knobs on the pedal itself. Aside from the convenience, you can store sound banks, individual tones, and settings and then simply upload them to the unit before recording or performing.
Another great benefit of these modern preamp pedals is that you can download patches that are preset sound profiles that other musicians have created and use them in your music. You can then adjust and tweak the settings as you like, make your sound, and then share that back!
It should also be noted that some pedal and gear manufacturers like Seymour Duncan produce power amp pedals that play the same role as the main amplifier. You could connect that directly to the speaker cabinet. If you used one of these, you would eliminate the need for a separate guitar amplifier.
Preamp Vs. Power Amplifier (What’s The Difference?)
Since you may have both preamp and power amp in your guitar amplifier, you may ask why you need both and why are they separated in the head unit? For starters, each amplifier section has a different role.
The preamp’s sole purpose is to raise the line voltage signal to where it can be boosted and amplified through the power amp – whether this is a head unit, PA, or mixer. Remember that the raw signal from the guitar or microphone is very low, so it first needs to be boosted sufficiently before it can be amplified.
The output signal would sound anemic if the preamp didn’t do this. You would hear a thin sound, lacking depth and volume, and without the preamps, you would never really hear the true tones of the guitar or the range on the vocals.
Once the preamp has done its work, the power amplifier takes over, boosting that line signal even more and increasing the volume of it through the speaker or speakers. That final signal that the audience or producers hear is the result of the preamp and power amp working together to produce your sound to its maximum color.
The power amplifier will take that preamp signal combined with the effects and boost it as loud as you need. Now, remember that the power amplifier only boosts what it gets, so the signal received is the one that has passed through all the effects you have, and that line signal is then smashed out through the power amp.
Why Are The Preamp And Power Sections Separate Inside Amplifiers?
The main reason for this is interference and temperature. Power amps use transformers to boost their signals, and these get pretty hot in the process. So if they were close together, they would risk overheating and failure.
Another reason is that the creation of electrical currents in the power amp’s massive transformer could result in noise and interference with the signals, so they are kept apart to prevent this from happening.
Now that we have a good insight into preamps and power amps let’s look at how preamps work with bass guitars, electric guitars, and microphones.
The Preamp With Bass And Electric Guitars
Preamps work quite similarly with bass and electric guitars as the line signal from these instruments is very low, and the preamps boost that signal. Still, they also provide other benefits as well (such as reducing noise).
The guitar is first plugged into the preamp (whether a pedal, module, or onboard unit) using the cable, and depending on whether your bass is active or passive will determine which input the line is connected to.
If your bass is ‘hot’ or active, you will plug that into the active input on the preamp, as plugging into the passive side would cause the signal to peak or ‘clip,’ creating a distorted sound. Most electric guitars are passive, i.e., they don’t have an internal amplifier and rely solely on the preamp and amplifier to achieve their output sound.
The first boost you look at on bass and electric guitar is the gain. While this means something a little different for microphones, the gain is the boost level of the guitar’s input signal, and you would turn it up until you reach the level you want.
Increasing gain can also lead to the rock distortion sound, which is often used in hard rock and metal. Many preamp pedals have additional distortion effect options that add greater distortion to the initial signal. You can also control the volume of those effects so you can set it as you want.
The next phase is EQ, where you can focus on tweaking the different frequency responses like bass, mid, and treble to fine-tune the sound. Using the EQs to set the tone is common practice, and increasing these levels will also increase the overall preamp output to the power amplifier.
With the EQs, you can cut or boost frequencies at the top, mid or low end, and this can add a good variety of options when it comes to specific songs or sounds and create cleaner, warmer or richer tones as needed.
EQs can come in parametric or graphic configurations; the only difference here is that the parametric uses knobs on each frequency band. In contrast, graphic uses sliders to set the frequency levels.
Once you have set the preamp EQs, you can move to the different effects your preamp pedal or module can offer, such as delay, reverb, and harmonizers. So that initial output signal from the guitar has now become a far more complex overall sound, thanks to the preamps!
Preamp Distortion Vs. Power Amp Distortion
Because the power amp section has more power, the distortion achieved is generally more aggressive or ‘ballsy’ than the preamp distortion, which usually has more mid-range punch. But using them both can create that power rock or metal sound, so you must play with each side to find the sound you want.
The wattage rating of your amplifier also plays a role as lower-powered amps can distort at relatively low volume, while higher-wattage amps can play clean at much higher volumes.
Preamps With Microphones
Unlike guitar preamps, microphone preamps will offer a slightly different result as distortion is not often used with vocal signals. However, EQ is still a major consideration when setting up the preamp signal on a microphone.
Preamps with microphones boost the signal; they also deliver the cleanest possible sound and representation of that voice by lowering noise levels, adding more gain and good headroom.
Good preamps will reduce hiss and noise, while lower-end products may add noise to the signal and lower transparency, which is the opposite of what you want from a vocal signal. The cleaner the sound, the better the preamp is.
Microphone preamps also offer the option to adjust and fine-tune the warmth and tone of the voice to a thinner or fatter sound. Experienced sound engineers will know how to use different microphones and preamps to generate the perfect style for the track or the artist.
Their flexibility and range of options available on preamps for microphones open up a new universe of possibilities for sound, tone, and effects allowing for greater expression of individuality when it comes to songs and the overall artist sound.
Another consideration for preamps is the consistency they offer, which applies to guitars and vocals. Whether you’re an artist or engineer, you will have certain go-to settings for color and tone that you can rely on, making the recording and setup process much simpler.
Because preamps come in various shapes and sizes, you could use a two-track preamp for simple solo recordings and then have a 16-channel setup if you needed to add other instruments like drums, so the preamps offer versatility in the studio or on stage.
Preamps do much more than boost the output signals to line levels. Using and setting the preamp properly, whether a pedal or integrated system, is crucial to achieving vocal and instrumental signals that will sound how you want them to once amplified.
Understanding how preamps and power amplifiers work together to produce the final signal will improve your skill in setting up and achieving the right tone, whether you are an artist or an engineer in the studio or on stage.