With its introduction in 2003, the portable and great-sounding AC-60 Acoustic Chorus Amplifier was an instant hit. Its dual-channel operation, built-in digital effects, and small size and portability have made it a consistent favorite among acoustic guitarists and other instrumentalists. Now, for those that need a little larger and louder alternative, the AC-60 has a big brother: the AC-90. Sporting a similar look and panel layout, the all-new AC-90 offers what the AC-60 offers, but with more power and a larger speaker compliment. Let’s take a look at this new acoustic instrument amp’s features in detail.

Acoustic Power
The AC-90 offers a little more beef than its little brother—90 watts of dynamic stereo power (45 watts + 45 watts) drives two 8" woofers and two tweeters, delivering crisp, clean, and accurate acoustic sound with a rich bottom end. The woofers utilize light and efficient neodymium magnets both for superior sound quality and weight reduction; at a gig-friendly 26 pounds, this amp’s extremely easy to transport. And, speaking of transport, the AC-90 comes standard with its own carrying bag, which includes a heavy-duty padded shoulder strap and two big side pockets for stowing cables and your favorite BOSS pedals. The bottom of the amp features an integrated tilt-back stand, and there’s also a mount for placing the AC-90 on a standard speaker stand.

Dual Channel Versatility
Like the AC-60, the AC-90 provides two separate channels. This allows you to connect two separate sources simultaneously, such as a guitar and microphone, two guitars, a guitar and a keyboard, and so on. This versatility lets you use the AC-90 as a mini-PA system as well as a guitar amplifier, making it one of the most flexible amps in its class.

Each channel has its own VOLUME, BASS, MIDDLE, and TREBLE controls and an on/off switch for the chorus effect (more on that coming up). The top channel is designated for an acoustic-electric guitar, with a standard ¼-inch input jack. The PICKUP switch lets you optimize the input for the type of pickup in your guitar, be it a piezo under-saddle type or a magnetic type. Additionally, this channel features a SHAPE switch, which allows you to engage a special EQ curve that boosts the low and high ranges and cuts the mid range. This is great for smoothing out the sometimes harsh and “quacky” sound of under-saddle piezo pickups.

The bottom channel is optimized for either mic or line level signals, and features a combo input jack that accommodates either an XLR connector or a ¼-inch plug. There’s a switch that allows you to set the input gain to match the source signal’s level, be it a microphone or a line-level source such as the output from an effects processor. If you’d like to plug in a condenser microphone, +48-volt phantom power can be provided from the jack when an XLR connector is plugged in.

Effects to Go
To sweeten your sound, the AC-90 offers some great sounding digital effects. The famous Roland stereo chorus is built-in, with three different types (SPACE, RICH, and WIDE) that are all optimized for acoustic instruments. The ingenious one-knob CHORUS control allows for selection of both chorus type and the depth of the effect, making it super-easy to dial in the desired chorus sound in the heat of a gig. For ambience, there’s a reverb/delay effect, also with a simple one-knob control for dialing in the effects’ sound. Like the AC-90’s chorus, both the reverb and delay are specially tailored to provide a sound that’s very complimentary to acoustic instruments.

Feedback Killer
Anyone that regularly plays amplified acoustic guitars (or other stringed instruments) knows that feedback can reek havoc at the most inopportune times. Feedback can occur when the sound of an amp’s speakers is loud enough to cause the instrument’s soundboard to vibrate on its own. This vibration usually occurs at the guitar’s resonant frequency, and produces a low “humming” sort of sound that is in turn re-amplified by the guitar’s pickup system and the amp, creating a “feedback loop.”

To help eliminate these feedback woes, the AC-90 provides an Anti-Feedback feature that “notches” out only the offending feedback frequency while leaving the rest of your sound intact. It’s very easy to use: when feedback occurs, just turn the ANTI-FEEDBACK knob to dial out the offending frequency manually, or turn the knob to AUTO and press START to automatically detect and eliminate the feedback.

Master Section and Rear Panel
The AC-90’s Master section provides a MASTER volume control for both channels, and a handy MUTE button to temporarily mute the speakers to eliminates pops when plugging and unplugging cables. There’s also a PHONES jack so you can practice with headphones. (When you plug headphones in, the AC-90’s speakers are muted.)

The rear panel offers an abundance of connectivity. LINE OUT jacks allow you to send the AC-90’s signal to a PA system or recording device. The sound is output in stereo via two XLR jacks, or summed to mono via a ¼-inch phone jack. The signal from these jacks is unaffected by the MASTER knob; this allows you to use the AC-90 as a personal stage monitor without affecting the feed to the alternate destination.

A DI OUT/TUNER OUT is provided on a ¼-inch TRS jack. It can function as alternate balanced line output, or, when used with a special Y-type cable, it can feed two separate unbalanced destinations. The MASTER control affects the level of this jack, but signals are still output when the MUTE switch is engaged. This makes this jack great for feeding a device such as tuner. Rounding out the outputs is a SUB WOOFER OUT, designed for connection to a powered sub woofer (such as the Roland KCW-1) so you can extend your low-frequency sound if desired.

Two pairs of AUX IN jacks—both RCA and ¼-inch—let you mix external sound sources such as a CD or MP3 player or drum machine with your mic and instrument. Finally, up to four optional footswitches can be connected to the two footswitch jacks for hands-free control of Mute, Anti-Feedback, Chorus on/off, and Reverb/Delay on/off.

Solid Choices
As you can see, the new AC-90 is chock full of great features for the acoustic musician. Did I mention it sounds great, too? With the AC-90, Roland offers an amp with lots of volume and versatility, yet in a surprisingly light and compact package. Of course, the venerable AC-60 still offers a smaller alternative if your amplification needs are less demanding. If you’re in the market for an impressive sounding acoustic amp or portable PA, get down to a Roland dealer and check out the great sounds and features the AC series has to offer.