A power supply unit (PSU) is plugged into a power grid wall outlet (aka socket) and it modifies the incoming AC-voltage in such a way that the pedals can be powered as the designer intended. Using a power supply correctly requires you to understand a few technical terms. Don’t be frightened by a little jargon – a quality PSU will make your life much easier. We will try our best to make the terminology accessible for the common musician.
When we say PSU output we mean the little female connectors that send the necessary power to your effects. On some power supplies several outputs are supplied by a common transformer section, which means these outputs have a shared ground (earth) connection. We recommend using only a single pedal for each section to avoid noisy ground loop humming. In some drastic cases you might even damage the power supply by running several effects off the same section. It depends on the brand and PSU model, whether a power supply has more than a single output per section. In any case, for pristine and hum-free operation we’d advise you to only connect a single pedal to each isolated section. This way each effect on the pedalboard is electronically isolated from the power feed of the other pedals. The exception to this rule comes in the form of special adapter cable, which will allow you to connect two effects without the danger of ground loops.
An isolated output means that the output’s ground potential is not shared with any other output.
If a power supply’s outputs are all connected to a common ground, humming ground loops can be formed, because both the guitar signal and the pedals’ power supply outputs are connected to same earth in different ways at the same time. The different ground connections can form a sort of “vicious circle” and become an antenna for picking up transformer hum and other unwanted electromagnetic noise. A properly isolated section is also isolated from the power grid’s ground, which goes a long way to prevent additional problems with the audio signal.
Using only isolated outputs makes it impossible for a ground loop to form, even when you’re using all effects on your pedalboard simultaneously. In principle almost all the PSUs Custom Boards sells have isolated outputs, meaning that the power supply unit is made up internally of a group of electronically separate little power supplies. This prevents the ground loop efficiently. The only exception is the T-Rex Fuel Tank Classic, which nevertheless has been designed so, that it will work in most situations where you’re using only analogue pedals.
If you have purchased all the parts and components but get a feeling that you might not be up to the task after all, we can make your pedalboard for you, using the components you have bought from us. Don’t worry, we won’t let anything go to waste.
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