What is the best acoustic guitar amplifier

All about acoustic guitar amplifiers

by Andreas Schulz,
(Image: Andreas Schulz)

With electric guitarists, the situation is clear: the amp, as an element influencing the sound, is part of the signal chain and has a decisive influence on the sound. So he's much more than just a neutral phonemaker. It's a little different in the world of acoustic guitar.

Most acoustic guitarists want their instrument to be amplified as naturally as possible. In short: They only want the sound that they know from their guitar purely acoustically, louder. However, it is quite complex to make this simple wish come true. In addition to the amp, the type of direct sound pick-up on or in the instrument also plays a decisive role. And that brings us back a little to the interactive interaction of several positions in the signal chain: instrument - pickup - amplifier.

With acoustic amps, too, you should make sure that the amplifier fits the pickup system of the guitar and adequately reproduces its strengths, perhaps even compensates for any weaknesses or imperfections in the pickup. The pickup or pickups should, in turn, match the instrument and reproduce its character as desired - see also the article on pickups.

Sound culture

The perfect acoustic guitar amplifier should therefore be a pure, linearly transmitting sound maker without its own sound coloring. Or? I remember an impressive concert by Chris Whitley. He played his old National Reso over a Fender tube amp with a crunch sound - and it sounded great, with a mixture of recognizable acoustic tone and pleasant distortion. Similar to Monte Montgomery, prototype of the acoustic rocker, which brings its extra stable built Alvarez / Yairi steel strings far into the saturated rock sound and works with compression and overdrive - but ultimately amplified by commercially available AER amplifiers.

So, when looking for a suitable acoustic amp, you should know whether you want the "characterless" linear loudspeaker or whether the amp should help shape the sound, at least in details? The answer to these questions indicates a tendency in the device class of acoustic amps. Because on the one hand you will find amplifiers that are based on studio equipment - the speakers are based on neutral studio monitors, the preamp design is reminiscent of channel strips on studio mixing consoles.

And then there are amps whose construction and design are based on electric guitar amplifiers. Not in the sound, mind you, but these devices usually belong to a somewhat rougher genre in terms of sound, they do not want to sound like studio boxes, but rather give the E-Acoustic its own voice with force and assertiveness - even if the last bit of naturalness may be sacrificed must become. There are many hybrids and mixed concepts between these poles.

Loudspeaker concepts

Representing the linear amps brand "Studiosound" are among others. Products from Schertler, Acus and, with a slightly different concept, also AER. The widespread mid-size amps often feature bi-amplified two-way systems. This means that two loudspeakers (e.g. an eight-inch speaker for low frequencies plus a tweeter) are each driven by their own power amplifiers.

Of course, there are also multi-way designs of the classic type, with an output stage and crossover, which are then used to drive the bass and tweeters together. Alternatively, broadband speakers can be used, mostly in the form of coaxial speakers with the tweeter integrated in the bass speaker. The technology of these amps has developed in such a way that supposedly small devices produce a considerable sound pressure and an impressively clean and clear sound.

As a contrast, let's look at how a well-known electric guitar amp manufacturer like Marshall solves the acoustic gain. Their AS50 or AS100 amps offer the typical Marshall design, come with 8-inch speakers plus tweeters and are considered to be extremely robust fellows who act assertively, but do not quite offer the hi-fi-like reference quality of studio-oriented colleagues. However, the popularity of these amps for many years shows that guitarists have different tastes and that not everyone prefers the clean and crystalline studio sound.

Manufacturers like Roland, on the other hand, rely on them Stereo playback and have two power amplifiers on board that drive two separate speaker combinations. Then the effects are also designed in stereo. The aim is a spatial sound that is perceived as "larger-than-life" and is a bit more impressive. Whether you like it and have a positive effect on the feel of the game, you should try it out calmly and preferably in a direct comparison.

Selection criteria

In order to narrow down the selection for the acoustic amplifier that suits your own needs, we go through the important criteria. Stand at the beginning Size and volume. Should the device be rather small and portable, or is a strong performance and appropriate volume in the foreground? When making this decision, you should go through the current application scenarios realistically and add some potential for future positive career jumps.

The next one decides Number of inputs and channels. If the amp is really only intended for the guitarist whose guitar has a simple pickup system, an equally simple one-channel amp is sufficient. If you have a more complex setup with several pickups, different instruments, additional vocals, other microphone signals or music recordings, you need an amplifier that can also record all of these sources and process them as independently as possible.

That is also important Outputs: You have to have suitable outputs available if your signal is to be amplified by a PA, if you want to make recordings or if you want to incorporate external effects. There should be at least one line output (jack) and a balanced DI output (XLR), and an effects loop with send and return.

Should the amp own Effects have on board? Reverb, which most amps have integrated today, is usually required here; there are also devices with additional effects such as delay or chorus. If you work with a pedalboard or other upstream equipment anyway, you can put this criterion at the back of the selection.

One should make sure that the Tone control is as flexible as possible, i.e. also includes a center control, and that as many signal paths as possible have their own equalizer. So you are prepared for everything and can adapt different sound sources so that the resulting common sound from the amp is optimized.

When amplifying acoustic guitars, a certain volume is required Feedback a theme. These are feedbacks in which the signal emitted by the loudspeaker is picked up again by the guitar's pickup system and sent back into the amplification chain, which, under unfavorable conditions, builds up and becomes a low-frequency roar or high-frequency howl. Both the loudspeakers of the amp and the ears of the musicians and the audience are acutely endangered. So it's good if the amplifier has appropriate tools such as phase reversal switches or notch filters on board.

connections

The more flexible the Entrances designed the better. There should be jack inputs and XLR inputs on board (they are also available as combination sockets). The input impedance is important: Passive pickups like some piezos and magnetic pickups like high-impedance inputs, active pickup systems are better off at low-impedance inputs. So ideal if you can switch the impedance; In addition, a level adjustment (gain), an LED that warns of overloading (clip) and a switch for a level reduction, so that very strong signals do not overload, are desirable.

If you want to connect a microphone, you need an XLR socket. If you work with condenser microphones, you need a switchable phantom power supply (48 V), which supplies the microphone with operating current. Musicians who want to amplify guitar and vocals with a combo amp should have the right inputs and, if possible, two channels with their own EQs.

Line inputs are used to record signals that have already been processed, such as music recordings, keyboards and drum computers. These do not necessarily have to have their own fully equipped channel, a volume control is sufficient. Such auxiliary inputs, usually implemented as jacks, sometimes also as cinch sockets, are often referred to as aux-in.

Both Outputs As a minimum, a balanced DI output (DI-Out or Balanced-Out) in the form of an XLR socket should be on board. If there is also a line-out - so much the better. At live events you never know what exactly to expect and how the environment will be equipped.

With well-equipped amps you can switch the DI-Out between pre and post. The Pre setting takes the signal directly after the input stage and before EQ and volume control. It is then independent of the other amp settings - ideal for forwarding the unadulterated signal to a PA for sound reinforcement in the hall, because changes made by the musician on the amp (perhaps necessary for the stage sound) do not affect the sound of the direct signal to the outside.

Sometimes the level of the DI-Out can be switched, which is welcomed by PA rental companies on site, sometimes you can also disconnect the socket (ground lift) if there is background noise from hum loops.

Regulator

The more extensive the control options of the amplifier, the better. You don't always have to take advantage of them, but when there is a need to improve the sound of something, you are happy to have the necessary tools available. A Volume control Per channel is of course basic equipment, an overall level potentiometer in the master area is also not bad ("Just make everything a little louder!").

An adjustable adjustment of the Input sensitivity (instead of only switchable in two positions) can be an advantage. The Tone control The fully equipped amp channels should include at least an effective three-band EQ (bass / middle / treble), if the middle control is semi-parametric (level and frequency) or fully parametric (level, frequency, filter quality), you have even more targeted intervention options.

Sometimes there are switchable ones Sound presets, in which a mid-range cut is combined with a bass and treble boost. Such a HiFi-like sound suits some game situations and instruments. Usually the reverb or effects control per channel follows, maybe a notch filter. There are also four-band EQs, in which the mids are more finely divided into low-mid and hi-mid. Or there is an additional presence or brilliance potentiometer on board in addition to the treble control, which regulates the frequency glitter in the uppermost areas.

Effects

Effects directly in the amplifier should be viewed as a desirable addition. The basic equipment with the required connections, channels, control options and suitable amplifier power / volume should play the more important role in the purchase decision. Many acoustic guitarists do not like overly striking effects.

However, standard is a reverb. Today there is almost no acoustic amp without reverb, usually implemented as a digital effect that is continuously mixed with the signal. There are also amplifiers with an analog spring reverb unit. What you prefer is a matter of taste, the digital reverbs try to reproduce the spatial sound as realistically as possible, a spring reverb also provides spatiality, but has an audible sound that not everyone finds desirable for acoustic guitars.

In the meantime, modern amps are sometimes equipped with digital multi-effects that can produce delay and / or chorus in addition to reverb. You shouldn't be blinded by the sheer list of possible sounds or presets. So that this can really be used, there are often no control options to adjust the effect sound to your own sound concept or the requirements of the music.

A preset delay is usually useless because it has nothing to do with the tempo of the music and then sounds washed out rather than enriching. When it comes to modulation effects like chorus, there are many flavors - the likelihood that a built-in and unchangeable chorus preset will fit exactly is rather low.

Another way to incorporate effects is Effect loops. A serial loop has sockets for send and return and is fully in the signal path when occupied. Usually there are no further control options on the amp, you have to set everything on the external effects device. Please note: The entire signal of the amplifier is processed with the serial loop effect, this cannot be controlled separately for the individual channels.

Parallel FX loops are more flexible. These are also connected via send / return sockets, but proportionally mixed with the signal. For this purpose, there are ideally mix or FX send pots per channel and a general FX return control in the master area of ​​the amp.

Creative acoustic guitarists who work specifically with effects and want to set the scene with distinctive sounds mostly rely on external effects that are used in front of the amplifier, mounted on a pedal board or designed as a flexibly switchable multi-FX pedal. Or they combine additional effects pedals with a very good reverb in the loop-in path.

Feedback

A tiresome topic when amplifying acoustic guitars is feedback, i.e. feedback loops that swing up to loud noise. Fortunately, there are effective antidotes. One of them is one Phase inversion. Depending on the position in relation to the amplifier, this can already be very effective. Those who move around while playing or watch a sporty stage show are unfortunately quickly out of the feedback-free comfort zone.

Guitarists / singers who are seated or standing still should use the phase inversion to find a position in which a full volume without feedback is possible. Phase switches are not only found on amps, but often also integrated directly into the guitar's preamp.

Some amps offer one Low cut filter on (could also be called Hi-Pass). The lowest frequencies are cut. Since nothing happens with a normal six-string in the standard tuning below approx. 80 Hz, you can lower this range. However, you cannot then let bass instruments such as baritone guitars or acoustic bass run through this signal path.

If the feedback is clearly limited to one frequency, then there is a Notch filter a very good tool. This is a narrow-band preset EQ with strong attenuation that is "tuned" precisely to the critical frequency. Narrow band, so that the sound change is as small as possible and only the bad feedback is combated. If, in addition to the frequency, the degree of reduction can also be set - all the better.

There are even “intelligent” digital notch filters that find their own operating point. In doing so, one provokes the beginning of feedback in a controlled manner and then activates the automatic feedback canceller, which lowers the evil frequency.

It is helpful to understand feedback in general. It can arise in several ways. On the one hand, by directly stimulating the guitar strings to resonate with certain tones or frequencies. In a very noisy stage environment, the entire guitar top can even resonate with the sound. This is usually a matter of feedback in the low or low-center frequency range.

Special stage guitars (E-Acoustics) are deliberately built to be a bit stiffer and less susceptible to vibrations in order not to favor this feedback. If you use a pickup system with a microphone component, you are more likely to be threatened by high-frequency feedback, direct microphone feedback is the hardest to get a grip on.

You can also try to work directly on the guitar. There are feedback bussers that close the guitar's sound hole and thus interrupt or at least make the feedback loop more difficult. The purely acoustic sound is of course severely curtailed, but you accept that in order to be able to play live loudly and without interference.

Purchase decision

After so much analysis of what is possible and desirable with acoustic amps, you should pause again and sort the information. The most important thing when making a purchase decision is the sound. The amp should sound the way you imagine it with the most frequently played guitars. If you have a good amp behind you, you feel safe and inspired - and play better and more freely. It should also be loud enough with a reasonable size and weight.

Then the equipment details follow. How many inputs and channels do I need for my specific live settings? Which control options are indispensable? Does the amp provoke feedback with its own sound, does it have any tools to reduce it? Please also remember that you can add additional equipment to an amp, such as external effects, upstream EQs.

So if an amp meets all the criteria wonderfully, and there is only one parameter missing to achieve perfection, it is perfectly legitimate to solve this one aspect outside of the amplifier.

There are also accessories for acoustic amps. Protective covers secure transport, special stands ensure safe operation and ideal alignment, some amps have a connection flange in the floor and can then be placed on a speaker stand. And now off to the stage!


Street Life: Battery Amps

If it is not about sheer volume and you do not need a lot of control options, but want to be as mobile as possible and, above all, independent of a power connection, you opt for a battery-powered amplifier.

This is interesting for street musicians or for guitarists who have small jobs as a “mobile band”. Of course also for the purely private area, think of the quarry pond, pool party and BBQ. Battery or rechargeable battery operated amps are available from € 100 to € 1500, from toy to professional version. These manufacturers have dealt particularly intensively with the topic and above all optimized the operating time: Roland, AER, Acus, Yamaha, Vox, Fender, Laney.


Alternatives

There are not only dedicated acoustic amps for amplifying acoustic instruments. Specialized small to medium-sized PA systems are also suitable for acoustic guitars and generally for typical unplugged playing situations. These are particularly recommended if you have to fill a larger location with sound or if you want to strengthen a band line-up.

A guitar duo or a singer / songwriter with guitar plus vocals can still be heard with one or two acoustic amps, but if additional voices, acoustic bass, harmonica, wind instruments and percussion are required, a small PA is recommended. A classic concept is followed here, there is a mixer, power amplifiers and boxes. Sometimes the power amplifiers are integrated into the mixer (power mixer) or directly into the speakers (active speakers).

The loudspeakers in turn can be full-range speakers (all loudspeakers are in a box, as a 2 or 3-way system) or divided into subwoofers plus satellites. The subwoofer only emits the low frequencies (a box is often sufficient), the satellites are much smaller and take on mids and highs. They are usually placed at ear level, on speaker stands or stand rods above the subwoofer.

Line arrays are also an interesting concept. The speakers are tall and narrow pillars in which many small loudspeakers do their job. These are slightly angled towards each other so that they radiate very broadly. The columns are supported by a bass loudspeaker in the base or can be drilled out at the bottom with an additional subwoofer.

There is also a connection palette, which is often sufficient for simple applications; the line array systems can be supplemented with a mixer for larger occupations and more channels. The interesting thing about it is - besides the sound and the different feel for the musicians - the fact that you can place these speakers on the stage in such a way that they also serve as a monitor.

The traditional small PAs, on the other hand, are intended for public address (PA stands for Public Address) and usually have to be supplemented by a monitor for stage sound. Small acoustic amps can also be used for this purpose - so there is definitely an overlap between acoustic amplifiers and PA systems.


>>> More information about acoustic guitars can be found in our Acoustic Guitars ABC <<<

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