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.