INTERVIEW: Buck Waller of ISP Technologies

You may have seen my review of the revolutionary ISP Technologies’ Decimator noise reduction pedal a while ago. The Decimator concept has evolved even further into the excellent Decimator G String, – my review of that one will be online tomorrow – but in the meantime I asked Decimator mastermind Buck Waller some questions about his groundbreaking designs.

What does the Decimator do differently to other noise gates, and why have other noise gates got it so wrong?
The most simplified noise reduction system is a noise gate. A noise gate works by simply switching the signal path open or closed so the signal is either on or off. The threshold is set so as to allow the desired signals to pass and to open the gate so no signal passes when the signal level decays to the point where the noise becomes undesirable. Most players find this undesirable since the gate will pop open and closed as the signal of the guitar gets near the threshold set point. For years downward expansion has been used as an alternative method of noise reduction and most professional studio noise gates actually use a method of downward expansion instead of a simplified noise gate. The typical professional studio noise gate will have an attack time allowing you to set how fast the expander opens and a release time or rate that determines how fast the expander attenuates after the single drops below the threshold point. This may provide acceptable performance in many applications such as a gate on drums where a single drum is fed through a gate to control the attack and release of a drum with a definable and repeatable waveform. The problem becomes evident when you try to apply this technology to a guitar signal, which can change hundreds of times in any given song. The guitarist is changing from staccato short fast playing to long sustained notes and everything in between and a pre-defined release of a gate or expander is a compromise at best. The Decimator is a single ended noise reduction system, not a noise gate, or a simple expander.

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REVIEW: ISP Decimator G-String


ISP Technologies was founded by Buck Waller, who previously revolutionised the things we don’t hear about guitar when he created the HUSH system for Rocktron. Noise types and requirements have changed a lot over the last few decades, and the ISP Decimator broke new ground a few years ago with its unprecedented tracking and sound quality, and the new Decimator G String takes things even further.

The Decimator series works a little differently to most noise gates. A regular noise gate will simply close the signal path when the input dips below a certain level. This can result in notes being chopped off unnaturally when you’re trying to hold a chord. The Decimator is completely different from this method. Instead it’s a single-ended noise reduction system which operates over a 1000 to 1 ratio using the company’s patented Time Vector Processing circuit. In plain english, this means the Decimator knows when you’re playing; when you’re not; and what to do about it.

Time Vector Processing refers to how the Decimator actually tracks the envelope of the input signal (instead of just using the mere presence of a signal above a threshold to determine whether the gate is open or closed). The best way of describing it is to imagine having a sound engineer continually adjusting the volume of the noise in perfect synchronicity with your playing.

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