Can a Preamp Be Used as an Amp?

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Can a preamp be used as an amp?

The answer to this question is no. In order to amplify an electric guitar, or any other instrument for that matter, you need an amplifier.

In a basic scenario, this simple analogy will help explain the difference between a preamp and an amp.

Think of a preamp as the motor of an engine. Its job is to generate the minimum level of power needed to get the engine started (turn it on).

Think of an amp as the petrol of an engine. It provides the primary source of power for the engine (keeps it running).

The preamp will do absolutely nothing without the amp. The amp is the power source that will ultimately amplify the electric guitar signals. So it’s pretty clear that your electric guitar will not sound any different if you use a preamp instead of an amp to amplify it.

Preamp vs amp

The main purpose of a preamp is to boost the volume of an audio signal. To understand how a preamp amplifies, let’s take a look at its name. Preamp stands for preamplifier, which basically means an amplifier that is prior to other devices. In other words, a preamp amplifies your audio signal before it’s fed to the actual power amplifier.

The preamp and power amp combo is the most common method of amplifier design because it’s an efficient and cost-effective way to boost the volume and improve audio quality. But it’s not the only role that a preamp can play. If you want more signal stability, bypassing the power amp, you can use it as a power amp and input your audio signal directly to the preamp.

This design results in an increase in signal quality and signal stability yet it still allows you to adjust the volume as you please. This is why preamps are often referred to as preamps/amps.

The answer

Is no, and here’s why.

When you are in the market for a tube preamp, or for amps for that matter, there are a number of features you should be looking for to make sure that you are buying quality equipment that will last.

Carefully read the description and specifications of each amp to ensure it meets your needs and specifications. In the case of a tube amp, one of the easiest indicators of a quality tube amp is class. Since tube amps require time and care to create, a higher class amp will have been given a higher priority of higher end parts, better craftsmanship, and more time by the manufacturer. Having said that, there are some manufacturers that knowingly or unknowingly sell amps at lower class ratings than what they should actually be. So reading the manufacturer’s specs will ensure that you know who you are dealing with.

Can you use a preamp without an amplifier?

When playing live, I only use the headphone out of the Line6 Pod for my amp. Some shows, I use both my Pod and my Boss GT-8 processor which allows me to use different settings on each. At home, I use my Pod cause it's only me. I don't need a big stack. The "Gig Mode" on the Pod is really good for achieving that guitar stack tone.

Another thing to think about is: is this a live rig or a recording rig? If your goal is to record, or maybe it's a studio practice rig, then you're probably better off using a cheap solid state practice amp. I have an Arguiound 212 that I power with the Pod and use for practice. That way, I can set the practice amp to a "clean" or "flat" setting and I don't have to worry about it with the tone.

It’s not strong enough

While a preamplifier supports a full-scale signal, an amplifier supports multiple signals. An amplifier has to be designed specifically to support musical instrument signals and by default it is designed to be strong enough to handle them. A preamp is not made to handle musical instrument signals, which is why it doesn’t have enough power.

Even if you could play at full volume through a preamp, the sound quality is never as good as using a full-fledged amplifier. This is why you need a separate amplifier for your speakers.

And since a preamp is designed primarily for preamplification, the sound quality is going to be slightly better when it’s used for performing with musical instruments.

It doesn’t do enough

I can honestly tell you that yes, you probably can power your headphones with this or even a similar value amplifier.

However, you won’t hear a huge difference between whatever comes out of the headphone jack on your computer. That’s because output from audio interfaces, computers, and other equipment with headphone jacks is usually limited. This is done to protect your equipment and avoid the risk of blowing your headphones.

While the volume can be significantly louder than plugging your headphones into your computer you shouldn’t expect an extremely significant difference. When you’re listening to music and all you care about is the music and not the heavy bass or the complex and detailed nuances, listening on a loud volume might be perfect for you.

Now if you’re an audiophile like me, you want more control and you want to hear and experience the music you love as the artist intended. In that case the headphone jack on whatever you’re plugging your headphones into simply won’t do the trick.

It isn’t necessary for an audio circuit

To be powered to amplify a signal. Of course, there are some circuits that will need a battery or another voltage source to be powered, but there are other circuits you can use as an amp that are only preamps.

Unless you’re designing a piece of equipment, you’ll rarely have the need to design your own preamp, but it is useful to know how they work in case you ever need to troubleshoot one. Below is a diagram of an active preamp to clarify how they work.

Active Preamps

Active preamps, as opposed to passive, rely on an outside voltage source to function. Active preamps are typically found in mixers, keyboards, and sound cards.

As you can see from the diagram, an active preamp can have an active gain stage or an active attenuator. Both circuits use active components, but they have different applications. The first circuit is actually a power amplifier circuit. It amplifies the signal coming in from the source. In this case, the signal is fed through an attenuator and not an amplifier. This is why the circuit is active and needs a power source. The second circuit is an active preamp circuit. It’s not designed to amplify the incoming signal, only to change it.

Tips for using a preamp in your system

If you have a tube preamp and you are looking to use a guitar amp, you can do so but do not expect a good tone. As you know, preamps are only meant to boost the guitar signal before the power stage. Although it is not entirely bad to use a preamp for the power stage, you will still hear hum noise as the preamp is not quiet.

The acceptable way to use a preamp in your system is to use it as a preamp. Then, to create a power stage, either use a solid-state power amp or use two preamp-output jacks in order to couple the preamp section with another tube power stage … or with a tube power stage.

You can do the same with a good solid-state amp, too. When you do this, you wind up with two power amps, but they are no longer working as separate units, running in parallel.

Each power amp section runs completely separately, as an entity unto itself. So the resistors affect the output of the preamp in the power stage, but no longer affect the power stage as the output. This is why you cannot use a preamp for the power stage. The preamp is not part of the circuit path that creates the output of the amp.

Where to put your preamp

To make a long story short: yes, you can use a preamp as an amp. Depending on what amp you're using now, you could probably combine it with a preamp and rescue some components.

Preamp and amp

Preamps and power amps are both integral parts of an electric guitar's setup. The preamp is used to boost an electric guitar pickup's signal-boosting the signal from a few volts to around thirty. This is essential, because it makes the signal strong enough to be sent to the guitar amp's power amp. The power amp then takes this signal and boosts the strength of the electronic signal.

Without the preamp, the pickup signal would be too weak and, therefore, unable to drive the power amp sufficiently-leading to loss of sound.

The main difference between a preamp and an amp is the processing that the signal goes through. A preamp usually takes the signal and just boosts the volume. An amp, on the other hand, combines a preamp with its own processing to handle the signal from the pickup.

Amp and preamp settings change the overall tonal quality, the volume, and the distortion of the signal. Independent preamp controls give maximum control over your sound. This flexibility is why many guitarists prefer to have an amp with preamp capabilities.

There is, however, a cheaper alternative, by using a preamp as an amp.

Preamp or interface?

One question I hear from time to time is whether a preamp can be used similarly to a guitar amp, on stage for a gig. Or if a preamp can be used without the matching power amp. The short answer is, it depends on the preamp. The longer answer is, it may be possible to use the preamp without the power amp, but the preamp will not work efficiently if not configured properly.

A preamp can be used as an amp, but they are not designed to drive speaker loads. Preamps are typically designed to drive headphones or to be connected to an already powered speaker cabinet. In order to use a preamp as an amp, you need it to create some form of virtual feedback loop. This is the same type of feedback loop that happens when the output of an amp is fed directly back into the input.

A preamp could be used in a setup like this, but it would need a way to power itself, either through an AC adapter, batteries, or a battery-powered amp. This is because the preamp needs power for its preamp tube, to act as an amplifier.

A preamp can be configured to do this, but you’ll need to figure out how to do that by yourself. I don’t know of any preamp that can be properly configured to act as an amp without the matching power amp.

Connecting the preamp to the amp

If you have a preamp that has a line out feature to connect directly into the power amp, you can plug the preamp’s signal directly into the power amp input. This means you won’t need a second speaker, but the sound will be fed into the power amp and out into the speakers.

The downside to this approach is that you won’t have a master volume control to change the volume of the preamp. Instead, you will need to adjust the volume on both the preamp and the power amp to compensate for changes in the volume. Not an ideal solution, but it can work if you don’t have a choice.

The alternative option is to connect your preamp to the power amp through the tone section. To do this, you need a separate speaker for the line out signal. You will also need a way to disable the speaker on your preamp. This is usually done through a speaker control switch.

It’s best to disable the built-in speaker to avoid damage to the power amps input. The downside to this solution is that you will need to have two power amps and two speakers. The preamp's full range speaker will feed the signal to the power amp's built in tone section or to the power amp's power amp input.

Some final thoughts

Quite a few people believe that a preamp can function as an amp.

However, its important to note that while they do appear to share some similarities, preamp and amps function in very different ways.

If you are looking to buy a new amplifier, it’s important to know why they work differently from preamps, even when they look identical.

A preamp can never be considered an amp because it does not provide sufficient volume to power speakers. For this reason, a preamp can only be used to amplify the signal coming from an instrument.

Conversely, an amp’s job is to amplify that signal, and send it to active speakers or headphones. This means using a preamp as an amp is the same as using a cell phone as a television. It makes about as much sense.

Aim to purchase an amp that is ideally suited to power your speakers. Speakers should be matched to their amp to guarantee optimal sound at all times.

Also, check the amount of power that your amp can handle. This information will be found in the amp’s user manual. For example, if your receiver is 100 watts, it probably would not be smart to pair it with an amp that is rated for 10 watts.

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I’ve seen the question confused and debated before. It causes some confusion in the guitar community, but this question actually has an easy answer.

Most people are looking for the straightforward answer. The short answer is:

Yes, a preamp can be used as a guitar amp.

And the longer answer is:

Absolutely. A preamp can be used as a guitar amp. You can use it for practice, as a warm up amp or to create different tones for recording. On the other hand, an amp cannot be used as a preamp.

If you break down the technical side of the question, you see that a preamp is the devices that hook up to a power source like a battery or power supply. They also connect to the amplifier or speaker and the input and output of the gear. For a basic setup, this is most of your devices. Your amp will plug into a preamp, which plugs into the guitar, headphones or a speaker.