Build Quality:4.9 out of 5 stars
Hardware:4.8 out of 5 stars
Electronics:4.8 out of 5 stars
Sound:4.8 out of 5 stars
Value:4.9 out of 5 stars
Average:4.8 out of 5 stars

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  • Excellent build-quality
  • Feedback Detection function which cuts down on feedback
  • Decent overall sound
  • Nice pack of features


  • On-board effects are not as good as the ones offered by a quality processor
  • The knobs are made out of plastic

Are you a gigging musician who plays on the acoustic guitar? Are you looking for an amplifier that will treat your instrument as if it were a queen of the world? Then you are in the right place, my friend. Today we are going to talk about the Behringer Ultracoustic ACX900, one of the best acoustic guitar amplifiers on the market. It has just the right amount of power for gigging, as well as all the essential features for home practice and tone perfection. If you want to find out more information about this model and acoustic guitar amplifiers in general, this article is definitely the way to go. Without further ado, let’s get started!


At first glance, Behringer Ultracoustic ACX900 looks like a fancy piece of equipment. It has a brown vinyl on the front, adding a vintage touch to this modern amplifier. What is more important is that it can generate 90 watts of power through two 8” BUGERA dual cone speakers. It has two channels with separate inputs, which allows you to plug in the microphone along with your acoustic guitar and gem with only one amplifier. You could also connect other instruments, such as keyboards and drums. Both channels have 16 on-board effects that utilize digital modeling to deliver the desired results. Behringer Ultracoustic ACX900 has a FBQ Equalizer with nine sliders, each of them controlling a specific frequency range. This way you can get super meticulous and modify any uneven frequency with simple adjustments. This bad boy is also packed with one of the most important features when it comes to acoustic guitar amplifiers: feedback elimination. Behringer Ultracoustic ACX900 has an on-board tuner, which allows you to keep your acoustic instrument always in tune. And finally, this amplifier has a single ¼” input for your acoustic instrument, the MIC jack for balanced XLR microphone, ¼” LINE input for any other instrument, a CD input for jamming along with your favorite music, a tuner output for plugging in an external tuner, an input for the foot controller, balanced XLR inputs for connecting the Ultracoustic ACX900 to the mixing desk, as well as Send and Return jacks for separate FX loops for both channels.


In order to make the tweaking process easier for you, Behringer decided to dedicate individual sections for both channels. This way you know perfectly which controllers belong to the guitar or mic channel, reducing the chances of making mistakes. To simplify everything even further, I will try to explain the functionalities of each knob in great detail.

The front panel starts with the “Instrument Channel” and a Phase switch. This little button reverses the phase of your signal by 180°, allowing you to eliminate the unwanted feedback. Just below it you will see a tuner switch, which activates the in-built tuner and enables you to tune your instrument. Then we have the Gain encoder, which sets the level of the channel. Next comes the FBQ Equalizer. The maximum damping or boosting range for each sliders is 12dB. There is a button (labelled as FBQ) which activates the FBQ Feedback Detection function, the functionality of which is pretty self-explanatory. Towards the end of this section we have the FX selector, which allows you to choose between 16 different effects (including different types of reverb, tremolo, delay, flanger, phaser and chorus). We also have an In/Out switch (activates the selected effect) and the FX Level (sets the level of the selected effect).

The second channel has the exact same controls with the same functionalities. And when it comes to the rare panel, the only knob we have there is the CD Level. This allows you to choose the volume of the external source with the amplifier itself. Nothing that complicated, don’t you think?


Everything about Behringer Ultracoustic ACX900 is built in a way that guarantees perfect sonic outcome. Since acoustic guitars have sort of a specific sound, they are a tad difficult to amplify. However, here we do not have this problem. Ultracoustic ACX900 not only delivers the quality tone, but it also emphasizes the best features of the acoustic instrument. This way you can proudly embrace the sound of your guitar and jam without any worries. Both channels have distinctive character, creating both clean and colored tones. Even though on-board effects are not as powerful and transparent as the ones provided on the processors, they are still usable if needed. If not, you could always connect your pedals to the effects loop and play that way. The feedback detection system and an EQ both work wonders when it comes to cutting down on feedback and shaping your tone to perfection. Behringer Ultracoustic ACX900 is simply a badass amplifier that will easily rock any stage.


There is not much left to say about Behringer Ultracoustic ACX900. It is sturdy and extremely well-built, which means it will last you for a while. Its sonic capabilities can easily compete with its high-end rivals. Everything about it falls into the right place: the price, the set of features and of course the sound. It will be quite hard to find the amplifier of the same level at such an affordable price. I dare you to listen to Behringer Ultracoustic ACX900 and make your final judgement accordingly. Spend an extra coin and trust me, it will be well-worth it. Good luck!

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