HOoP Explained (Phase inverter)
Our trademark sound. The HOoP. But what is it exactly? First of all let’s start by saying that the HOoP is nothing new, we have just found a way to embrace it with simplicity that makes it easy to play and not have to think about it.
To understand the HOoP we must look back to an earlier blog: “Understanding your guitar’s Tone circuit”. This article explains a capacitor’s ability to filter high frequencies and shunt them to ground. We employ the same frequency filtering effect of a capacitor to achieve the HOoP sound. “You still haven’t explained what HOoP is…….I’m confused”. To put it simply, HOoP stands for Half Out of Phase. Lets first take a look at an Out of Phase sound. An out of phase pickup is one that has it’s positive and negative leads attached in reverse. This in turn puts it out of phase with the other pickups. The effect will only be heard when BOTH pickups are on, but the result is dramatic! An out of phase sound first became popular on instruments such as the Jazzmaster which had various switches to perform this operation. Some early Stratocaster players also noticed the Out of Phase effect when experimenting with the “notch” positions which were once only accessible through modification. The Out of Phase sound became popular with surf musicians as it produces a very low power almost half-cracked wah sound.
To understand HOoP we must understand WHY the Out of Phase pickups sound the way they do. A pickup is an electromagnet. It functions much the same as a crankshaft sensor on a common automobile. It is long strands of fine wire wrapped around a magnet. When we pass a magnetic material (your strings) back and forth in front of the pickups the magnetic field gets disturbed. Because of the coil windings, it makes a sort of electro-representation of the vibration of the strings. YOUR music! When viewed with an oscilloscope, this small electrical current makes a wave. If two pickups are on at the same time, they are producing the same wave because they are both being activated by the same strings. By physically flipping the leads over, that wave would flip upside down on the scope. It is a simple matter of physics that an equal and opposite wave will cancel and result in nothing. Just like a wave in the ocean coming to shore would be stopped by an equal wave headed back out to sea. The same goes for music. The resulting low-power Out of Phase sound are all the frequencies that are left and could not cancel out.
“Okay, now I understand Out of Phase sound, but how do you get HALF Out of Phase?” Half Out of Phase is a term used when a resistor/capacitor network is used to selectively choose the frequencies that will cancel. (Remember the effect will still only be heard when two pickups are on at the same time). This selective cancellation is made by employing the high-pass filter properties of a capacitor once again but this time in a different way. Typically a DPDT switch will be used to make the transition and when in the activated position, one pickup will be connected to ground through the R/C network so, essentially only half of the frequencies will be allowed to reach the output jack at all. The desired effect here is that only the high frequencies of one pickup are allowed to cancel any frequencies at all from the other. The result winds up being a very musical and playable tone setting which is sensitive to pick attack and also how high you play in the register. The higher the notes (fundamental or harmonic) the greater the cancelling effect. The HOoP leaves all the lower frequencies in tact while canceling more and more as you play up the scale. Some claim the HOoP has the ability to mimic a Stratocaster’s Neck-Middle position. Many different capacitor material types, and cap/resistor values can be used in experimentation to find that perfect “in between” sound your looking for. The HOoP is great for playing lead or rhythm and gives a unique color and feel to your guitar.