ISP Technologies Decimator Pedal & Decimator ProRack G

Guitarists have wrestled with noise ever since the emergence of amplification. Humbucking pickups have certainly helped tame noise generated by electromagnetic sources, but with the parade of effects pedals that has become de rigueur for many players, post-guitar-generated noise reigns as a serious hassle in many situations. Noise reduction technology has long been used to deal with this problem, however, ISP’s new single-channel Decimator pedal and dual-channel ProRackG rack unit employ a unique Time Vector Processing system that, according to manufacturer, automatically determines the attack and release times to provide an improved response to staccato single notes. It also provides for a ripple-free handling of sustained notes and chords throughout their extended natural decay.

Housed in a sturdy, chromed metal enclosure, the Decimator ($149 retail/$119 street) sports a wide, hinged stompswitch with the battery compartment beneath it. Features include single input and output jacks, a Threshold control, an LED indicator, and a standard center-negative input for a 9-volt DC supply (not included). The Decimator is a snap to operate: Simply turn down your guitar, and then rotate the Threshold knob clockwise from its –70dB starting point toward its +10dB terminus until the noise floor vanishes. Further clockwise tweaks might be required when the guitar’s volume is wound back up, but that’s basically all there is to it.

With my ’64 Stratocaster feeding a fuzz, a compressor, an overdrive and a chorus pedal, the Decimator did an admirable job of cleaning up the noisy signal. Used ahead of the amp as well as in the effects loop, it even did a fine job on computer monitor-generated noise in my home studio. Moderate settings handled both clean and dirty signals well, but when running serious fuzz and distortion, an extra twist of the Threshold knob was often needed to fully nuke the noise. Such higher Threshold settings occasionally tromped on any mellow passages when the pedals were clicked off.

That’s where the ProRackG ($449 retail/$399 street) comes in. Designed especially for high-gain applications, the 1U device sports two channels of noise reduction. Channel 1 is assigned to the amp’s input to tackle 50- or 60-cycle hum and computer monitor or fluorescent light noise, while Channel 2 is patched simultaneously into the amp’s effects loop to handle the noise generated by high-gain preamp stages. Along with a Threshold control, each channel has a 2-position switch (–10dB or +4dB) for matching effects loop levels and an In/Out switch. Both channels share a Filter Tracking control that fine-tunes the built-in dynamic filter. The ProRackG easily dealt with the hum and hiss from the high-gain rigs I tested it with, but in order to work most effectively at getting rid of preamp noise, channel 2 needs to be patched into a series effects loop. If your amp has a parallel loop, it must be set for full effects mix.