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Big Briar Moogerfooger CP-251 Review

3/1/2001

Moogerfooger CP-251 Control ProcessorThanks to their voltage control-capabilities, the effects of Big Briar's Moogerfooger line blur the distinction between traditional floor-bound stomp boxes and analog synthesizer modules. In an attempt to mold the product line into a full-fledged modular synth system, Big Briar has introduced the Moogerfooger CP-251 Control Processor ($299).

As the name suggests, the CP-251 works with control voltages rather than audio signals, and Big Briar cleverly housed eight independent control processors in one small box. The processors include a mixer, lag processor, voltage-controllable LFO, noise generator, sample and hold, two attenuators, and a four-way multiple. Together, these features provide a useful tool kit for creating complex patches between Moogerfooger products, analog synths, and any other device that uses control voltages.

Due ProcessThe CP-251, measuring 5.25 inches tall and 9.5 inches wide, is slightly larger than a VHS video cassette, and you can place it in a rack-mount unit by removing the wooden sides. The CP-251 uses a +9V wall wart and includes two power inputs - one on the side, for use when the CP-251 is on a table, and one on the bottom, for use when the unit is rack-mounted.

The CP-251's 1/4-inch jacks accept 2-conductor (TS) or 3-conductor (TRS) plugs. The eight red-ringed input jacks are active and used for powering expression pedals, such as the Moogerfooger EP-1. The four-input mixer, for example, has two active pedal inputs, individual level controls for inputs one and two, and a master level control. In addition, you can add or subtract as much as five volts from the mixed signal by using the Offset control. The mixer has two outputs; the signal of the second output is the inverse of the first. You can create simultaneous melodic patterns in contrary motion by using both outputs with a pair of voltage-controlled oscillators (VCOs).

The Lag Processor offers independent control over a signal's rise and fall time. You can use this to add portamento between notes or to reshape a square-wave input into sawtooth and sine waves.

Two of the CP-251's sections - LFO and Noise - produce audio-rate signals. Noise is available from a single output jack. The LFO features an active input and has dedicated triangle- and square-wave outputs. The LFO frequency range is from 0.2 to 50 Hz, but it can be extended to 0.02 and 100 Hz using a control voltage.

The CP-251's Sample-and-Hold circuit features two active CV inputs. Nevertheless, the Noise module is conveniently normalled to the voltage input, and the LFO square-wave is normalled to the trigger input, which lets you use the Sample and Hold without patch cords. When used in this configuration to control a VCO, Sample and Hold provides a steady stream of randomized pitches, with the tempo controlled by the LFO's frequency.

Like the Mixer, Sample and Hold has two outputs. The first is the direct output of the sampled voltage. Before the signal reaches the second output, however, a lowpass filter smooths the signal's contour. The LFO Rate knob determines the degree of smoothing by controlling the lowpass filter's cutoff frequency.

The remaining processors - two attenuators and a four-way multiple - may seem boring compared with the other processors, but they are just as useful. The attenuators are great for quantifying the level of a control signal, such as an expression pedal's voltage range. Each attenuator has an input, an output, and a control for varying the signal level.

The Four-Way Multiple creates up to three copies of an input signal and works with both voltage and audio signals. The Multiple includes an active input, so you can send the signal from an expression pedal to as many as three destinations.

One with EverythingThe CP-251's manual is highly informative. It includes a basic tutorial about the use of voltages for control, an explanation of each of the CP-251's processors, and sample patches for using the CP-251 with other Moogerfooger products.

Although the Big Briar CP-251 is priced in line with most single-process analog-synthesizer modules, it's a true bargain when you consider the amount of processing power it gives you. The CP-251 is an essential purchase for any serious user of voltage-controllable gear.

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