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.

What challenges did you run into when designing the Decimator?
Regarding the challenges we ran into when designing the Decimator. As you may know, we are the original Rocktron Engineering team and I am the one who designed all of the HUSH technology. There were 6 patents that issued covering the HUSH technology and so my biggest challenge was to design a better noise reduction system and not infringe any of the 6 HUSH patents. The HUSH system was adaptive over about a 10 to 1 range where it will adapt the release somewhat based on the decay time of the input signal. By contrast the Decimator is adaptive over a 1000 to 1 ratio and uses our now patented Time Vector Processing circuit. I have attached the white paper that gives more details on the Time Vector Processing circuit, which was a total departure from how the HUSH control circuit works and far more effective and transparent.

What is the difference between the Decimator pedal and the G String Decimator?
The Original Decimator pedal has an input and output jack and is designed to go between the guitar and amp or in the effects loop. When you insert the pedal in the effects loop and adjust the threshold to remove high gain noise in the high gain setting of the amp and or overdrive pedals and then switch to a clean setting the threshold will need to be adjusted or you will need to switch off the Decimator pedal. By contrast, with the G-String pedal the guitar is inserted into the guitar input and guitar output feeds the input of the chain and you then can insert the Decimator IN and OUT circuit into the effects loop. This allows the Decimator control circuit to track the guitar signal directly and puts the actual noise reduction circuit in the effects loop. Now switching from high gain to clean will not affect the signal seen at the input of the level detection circuit since this is reading the actual guitar signal. This means that you can change any setting on your amplifier or gain pedals and never need to change the threshold on the Decimator G-String pedal.

Do the noise suppression needs of guitarists differ today from guitarists 20 years ago?
I don’t think in general there has been a major change but many metal players are running even higher levels of gain which means the noise reduction needs to be even more effective.

Will there ever be a way to stop that mobile phone chatter sound from coming through speakers?
The phone chatter is induced RFI interference picked up by the guitar, rectified and amplified. The Decimator will remove this noise if it is not higher than the threshold setting. It is possible to have a cell phone so close to the guitar that it would require an extreme setting of the threshold but in general this typical noise picked up by the guitar will easily be removed with the Decimator.

The Decimator circuit is also included in the THETA head. What was your concept for the THETA?
The THETA was designed with more gain than any other amplifier on the market. It has front end preamplifiers that are used to overdrive the distortion and clean channels. With the gain on the distortion channel and input preamp up all the way there is over 150db of gain. This simply is not useable without the Decimator circuit to clean up the gain noise. The Decimator was an integral part of the design process and in part allows the amplifier to offer higher gain than available before.


Thanks to Dominant Music!

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