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What is ground? Baby, don't hurt me!

Sebastien Vezina

While I would very much like to talk about love, today we will discuss something else entirely. You’ve seen the name and the quirky little symbol, in our own branding, even. You can’t speak about electronics without mentioning ground and, in fact, any circuit by definition has a ground otherwise it’s just not a circuit.

The electrical ground can usually be described as the point of least impedance (or resistance). If an electrical charge has a clear path to ground, you can be sure it’s going there and nowhere else. Mathematically speaking, that’s not true. Kirchoff’s law says current will go everywhere it can, but Ohm’s says that more current will go where there is less resistance. There is no such thing as “no resistance” so while most of the current will go straight to ground, a tiny wee bit of charge will still follow the other paths. We’ll get to this in a future post. For practical purposes, it’s true enough.

Why is it called “ground”, anyway? Way back when, in the days of yore when people used telegraphs instead of the Internet, they noticed that the actual earth worked as a current return path (for sciencey reasons) and it stuck. Your house probably has a connection to earth. Fortunately, that doesn’t quite mean you need to take a wire from your pedals and bury it or drop half a pound of dirt in your enclosures just yet.

Let’s take a look at what a voltage is. A voltage is not an absolute measure. You can’t say “that point right there has 9 volts” as if they were apples because it doesn’t mean anything. A voltage is a differential measure of potential energy between two points if they were connected. The resistance between those two points would define the amount of current developed by that voltage. Wait, that’s Ohm’s law again! Dude and his law are just everywhere. When we say a battery “has 9 volts” it means there is 9 volts of potential between the anode (positive pole) and the cathode (negative pole). Form a circuit between the two and you’ll get the full glory of its whole 9 volts until its charge is depleted. In that particular case, the point of least impedance is the cathode.

In a circuit, most potential measurements are made relative to ground, making it what we call a reference point. We say ground is 0 volts because, in reference to itself, there is indeed a potential of 0 volts but the same can be said of any point in a circuit. If you turn your measurement around and decide that the anode of your battery is your new reference point, your ground, the cathode will have a potential of negative (-)9 volts relative to it. That actually leads to a pretty neat trick we call a virtual ground, that has many uses in guitar pedals.

Most modern overdrive pedals use a standard 9 volts DC supply. Battery or wall wart, doesn’t matter. You might’ve heard that in some cases, using an 18 volts supply might give you more gain or more headroom (disclaimer: before sticking any power supply to a pedal, triple check with the pedal manufacturer if you can actually do that otherwise you just might fry it - we warned you). That’s great but what if you don’t have or want to buy an 18 volts power supply? We got you, bro.

Further down the line we’ll talk about a nifty little device called a voltage converter. These puppies use internal oscillators and filters to do simple operations on a DC voltage such as inverting or doubling. That might be hella confusing right now but that’s ok. 

Using a voltage converter, you can feed its input a 9vdc supply and on the output, get another voltage that has the same potential in reference to ground but with a reversed polarity: -9vdc. Knowing that, you can say that the potential between the supply and the voltage converter’s output is 9v - (-9v), so 18v! See where this is going? You can use that -9vdc supply as a virtual ground for your circuit, in which case the supply, in reference to ground, becomes 18v. 

Mind = blown.

Ground is a fundamental part of any electrical or electronic circuit and while it seems very simple at first - the subject can become quite complex. For the moment, remember these:

    - Ground is a reference point for measurements
    - Ground is where current wants to go

Questions and comments are more than welcome, just below!

Tata