What Is A Guitar Amp Head?

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what is a guitar amp head

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If you’re new to guitar or looking to buy your first serious amp, you might be confused by all the terminology you’re seeing.

One question many new guitarists have is: What is a guitar amp head, and why do people use them?

A guitar amp head, short for amplifier head, is a piece of equipment that houses the power and tone functions like other amplifiers, but lacks any speakers. Instead, amp heads are connected to speaker cabinets of various sizes, depending on the player’s preference.

An amplifier head isn’t likely to be your first purchase, but they’re very useful pieces of gear, and they have a long history in rock n’ roll. Let’s look at what an amp head does as well as why you might — or might not — want one.

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What Are The Different Types Of Amplifier?

When looking at amps you’re faced with a lot of possibly confusing terms and specifications. In general, there are two major kinds of amps: amplifier heads and amplifier combos.

There is another, more niche setup, where players use a dedicated power amp and preamp in a rack-case mount, but as that essentially creates a DIY amplifier head, we’re not going to cover it.

An amplifier head is a separate unit that houses a preamp, which takes the signal from the guitar and gives the player control over the volume of that signal, as well as over the tone and basic EQ settings, and the power amp, which converts that signal into an electrical impulse that can drive a speaker.

Generally speaking, it’s the preamp that gives amplifiers their distinct sound, which is one reason why modelling amps can easily switch between models. The power amp will also contribute to the overall sound, but the main tone and color come from preamp more than anything else.

In order to use an amp head in a performance, you need to use the head to drive a speaker cabinet. Normally when you buy the head you’ll also get a cabinet.

This video is an in-depth look at how a tube amplifier head is built, focusing on a well-known DIY design that’s available as a kit.

A combo amplifier is a single package that contains the preamp, power amp stage and a speaker. Combos are often more compact and transportable than an amp head and speaker cabinet package.

Why Do Players Use An Amp Head?

In addition to often being smaller and more portable, combos are also available in a far wider price range than amplifier heads. Heads are generally more expensive and you also need to buy a speaker cabinet.

Those seem like pretty big advantages for combo amps, and they certainly can be, but there’s clearly a reason that some players still use an amplifier head and speaker cabinets today. So what do they offer?

While amp combos can come in a range of sizes and wattage, from tiny to huge, they’re somewhat limited in the speaker arrangement they can offer. Some, like Fender’s legendary Bassman, use four speakers, but most top out at two.

And ask anyone who has ever had to carry a tube combo amplifier with two 12-inch speakers up multiple flights of stairs how “portable” they really are.

Here’s another thing to consider: There’s more than just the wattage of the amp when it comes to the apparent volume you’re putting out. Speaker size, as well as the number of speakers also plays a role.

That is one reason that amp heads became so widespread. Musicians don’t always know what to expect when it comes to the sound system available at gigs. A 100 watt amp head with two speaker cabinets, each with four 12 inch speakers. is going to put out more sound than a 100 watt combo amp with just two 12 inch speakers, for example.

Do Amp Heads Have Speakers?

Normally, when you buy an amp head, you’re just buying the head itself, without speakers. There is often a matching speaker set — or, in some cases, multiple choices — with the head, but unless there’s a package deal, they’re sold separately.

Part of they long-time mythos of amplifier heads is the full vs. half stack. In the 1960s, amp company Marshall sold its amplifier heads with either one speaker cabinet with four 12 inch speakers — the half stack — or two such cabinets — the full stack.

This video looks at situations when you might not want the full stack.

For decades, and for plenty of players still today, the image of a guitarist on stage with either a full stack or — if they’re playing a stadium — a whole wall of massive speaker cabinets was the sign of a player who had really made it.

But have you ever tried to get two four x 12 speaker cabinets into the trunk or hatchback of a car? Or had to live with them taking up room in your already tiny studio apartment?

Like most things, the idea can be more appealing than the reality.

That’s one reason there are multiple options available for both amplifier head power and speaker cabinet size and arrangement. You can buy single speaker setups, which might be a good choice for a smaller room or for a practice space, as well as dual and quad cabinets.

Most, but by no means all, speaker cabinets use 12 inch speakers, which are the largest speaker commonly used for guitar amps in general. Larger speakers like 15 inch or even 18 inch are found in bass amplifiers or sound reinforcement applications, but rarely in guitar amps.

Some cabinets use smaller speakers, again, those are often pitched as good for practice or for smaller spaces, where a four x 12 cabinet would be overkill.

Can You Play With Just An Amplifier Head?

Say you were given an amp head but no speaker cabinet — could you use it to play while you saved your pennies for a proper speaker cabinet?

The answer, as so often, is maybe, because it depends a lot on the amplifier head you have and the rest of your setup. Many newer amplifier heads have a headphone out jack that you can use in place of speakers. Some even have a USB out so you can plug directly into your computer.

On older amp heads, though, you’re not going to find a headphone out. Instead, you’ll likely find a few output options, all using 1/4 inch jacks, with a number and a symbol.

That refers to the output impedance, or the resistance level of speaker that should be plugged into that jack. If that is all you have, you can’t plug headphones straight into the amp head.

Doing that will cause unpleasant distortion at best and, depending on what kind of amp you’re using, could cause some damage. That’s because some power amps that use tubes instead of transistors need to have matched output impedance so they function properly.

If you don’t have a speaker cabinet, you can use a direct in box, sometimes called a DI box, with the proper impedance and then plug into a USB audio interface, which you can use to listen to the amp. This is a complex setup, though.

Speaking of playing without speakers, I mentioned earlier that many guitarists consider the image of a player standing in front of a wall of speaker cabinets to be the ultimate in guitar heroics. While you’ll still see those walls of speakers at shows, what you won’t get is the sound they make, because they’re mostly for show.

Full and half stacks became popular in the 1960s and 1970s, when sound reinforcement was still in its infancy. With modern speaker technology, guitarists don’t need so many speakers on their amps to reach the crowd.

Advancements in stage and in-ear monitors also means that the secondary function of those speakers — making sure the guitarist and the band could hear things is no longer necessary, either. Instead, players in larger venues will often do what we mentioned earlier and plug their amp head into a DI box to match impedance, and then send that to the sound engineer.

That can be mixed and sent to the monitors and front of house with the rest of the band.

The big walls of speakers still look really cool, though.

What Is An Amp Head Used For?

With all that, you might wonder why anyone even uses an amplifier head anymore. After all, most new combo amplifiers have a speaker out function, so you can use them on stage in the same way as an amp head.

Since you don’t need the raw power or speaker size you can go with whatever size and power level works for you, which could lead to a much more compact and portable rig.

And that certainly is possible. But not every player wants to go that way.

After all, music is about expression through sound. That mostly concerns what comes out, but anyone who has ever played music can tell you that how you play and what you use have an effect, as well.

Beyond that there are practical reasons. Plenty of touring musicians regularly face venues where they don’t have access to the high quality sound reinforcement I mentioned above.

Think of a rural county fair with a small stage at the edge of a huge field. A small combo won’t cut it in those conditions.

Musical style also plays a part in the choice. While both amplifier heads and combo amps are available in a wide range of power levels, amp heads tend to be more powerful.

Many of the heads on the market at 50 watt units, 100 watt units, or even more powerful. They also tend to be more focused on super high gain sounds, suitable for hard rock and metal genres.

Conclusion

When musicians today have more choices than ever for amps, from modelling combos that can mimic a wide range of tones to hand wired boutique combos, it can seem like the guitar amp head might be obsolete.

But while there might be fewer amp head choices today than combo amp choices, there is still a huge range out there, from five watt mini heads designed for practice and recording to the huge heads we talked about earlier. That alone shows how many players still want to use an amplifier head.