Over the years, DigiTech has been one of the most prolific manufacturers of guitar processors. One of its most recent products is the RP50 ($99.95), which offers 24-bit processing, a wide variety of amp models, and a large selection of effects for a very low price.

The stompbox-size unit features a tuner and a basic, playback-only drum machine. DigiTech has also included a ¼-inch Control In input that lets you use any standard passive volume pedal as an expression pedal to control volume and user-selectable effects parameters.

The RP50's controls include two large footswitches for selecting patches, and a series of smaller buttons for editing and drum-machine functions. There's a 2-character LED display as well as a series of LED-status lights to show such things as which effects are active and which are ready to be edited.

You edit by choosing from a menu of presets for each effect or model in the RP50. Although this method doesn't permit direct parameter editing in most cases, it does make it easy to quickly dial up sounds.

Each patch can have up to eight effects modules active at a time; choices are Pickup/Wah, Compressor, Amp Model, Noise Gate, EQ, Chorus/Mod, Delay, and Reverb. You simply scroll between the modules with the Edit/Effect buttons and choose individual effect settings with the Value/Master Volume buttons. Easy.

However, it's not always so easy to figure out what the unit's 2-character LED is trying to tell you. It displays lowercase characters to designate different categories within each effects module, and — because of the graphic limitations of LEDs — these can be hard to decipher in some cases. You'll want to either memorize the symbols or have the manual close at hand when you are editing. When you're ready to save, 40 user presets are available. (There are also 40 factory presets.)

The RP50's back panel is simplicity itself. It contains a single ¼-inch input and a ¼-inch stereo TRS output that can also be used for headphones. The unit runs on six AA batteries (according to DigiTech, you can get more than 15 hours of battery life) or the optional PS200R AC adapter ($24.95).

The RP50 uses DigiTech's Audio DNA DSP chip (the same one used in DigiTech's Genesis- and GNX-series processors) and has 12 types of amp models, including Blackface, Boutique, Rectifier, Hot Rod, Classic Tweed, British Combo, Clean Tube, British Stack, Crunchy Tube Combo, High Gain, Vintage Fuzz, and Acoustic Guitar. Each model offers a choice of nine gain levels, except Acoustic Guitar, which has only one.

In my opinion, most of the models sounded best at their higher gain settings. I particularly liked the British Stack, High Gain, and Crunchy Tube Combo models, which were creamy and fat. The clean models — Blackface and Acoustic Guitar, for example — sounded much less convincing.

The RP50 also has cabinet modeling, which is useful if you're going direct into a sound system or recording console, or listening through headphones.

The Chorus/Mod module offers an impressively wide range of effects, including Chorus, Flanger, Phaser, Tremolo, Panner (auto pan), Vibrato, Rotary Speaker, Auto Ya (like an auto wah but with a ya sound), Envelope Filter (auto wah), Detune, Pitch Shift, and Whammy. Only one of these can be active at a time; you get to choose from nine presets for each effect.

The Delay module has three basic settings: Mono, Analog, and Ping Pong. It allows you to set delay times as short as 10 ms or as long as 2 full seconds, and you can choose several feedback and wet/dry settings. There are six types of digital reverb to choose from: Room, Hall, Plate, Church, Arena, and Spring.

In addition, the RP50 has a compressor and a noise gate that are independent of the other effects. The gate works nicely to keep the unit's output quiet, but the compressor seemed to introduce a tiny delay into the attack of each note, which I found disconcerting.

The RP50's drum playback section gives you the choice of 30 preset patterns or a metronome click. Although it's not programmable, it's a cool feature to have, especially for practicing and songwriting.

You access the built-in tuner by pushing the two front-panel switches simultaneously. A series of 13 LEDs shows you when you're in tune. The tuner is accurate and easy to use.

Overall, the RP50 has an impressive array of features — including amp models, effects, cabinet modeling, a drum machine, and a tuner — for a very low price. However, in order to get it to market so inexpensively, DigiTech did have to make some compromises, such as the limited LED display and the lack of parameter editing. As a result, the unit will appeal more to entry-level players than working guitarists. That said, I can see a gigging player buying one to use as a backup to a more expensive multi-effects unit or as in inexpensive programmable stompbox to supplement an existing pedalboard setup. (Imagine all the effects it would add to your arsenal in one swoop.) It would also shine as an ultraportable processor for rehearsals, songwriting sessions, and other times when it's not convenient to carry around a full rig.

▪ Rating (out of 5): 3.5