Today we unravel how to navigate pedal voltages, polarities and connectors when it comes to pedal boards.
How to power your pedal board is such a technical part of the pedalboard process that we’ll be back in a week with a second part.
In the early days of guitar pedals, every designer did what they wanted in terms of pedal voltage requirements: 3V, 4.5V, 6V, 9V, 12V, 18V – Anything goes!
To this day there is a legacy of odd pedal supply voltages when assembling pieces to power your pedal board.
Eventually, a defacto standard emerged, settling on 9VDC (direct current) as the voltage.
It was a natural choice because of the availability of compact 9V batteries that could supply enough power to the simple pedals of the day. The AC/DC power adapters (wall warts) that followed were DC because it made them an easy substitute for a battery.
Moving into modern times, the increased power demands of pedal electronics gives new reasons to deviate from 9VDC.
In some cases higher voltage is needed for more headroom so the signal won’t be clipped and distorted.
In other cases, more power is needed for the electronics. The power can be increased either by increasing the voltage, say to 12VDC or 18VDC, or keeping the voltage at 9VDC but increasing the current (milliamps) supplied by the power adapter. In either case, neither a 9V battery nor a 9VDC power adapter can do the job. Moving even further from 9VDC, some pedal designers decided to rely on AC (alternating current) rather than DC from power adapters because they put some of the AC to DC conversion electronics into the pedal itself.
The result of all of this is a wide combination of voltages, currents and AC/DC types. In turn, this has created a host of related plugs, jacks and adapters. Knowing what-is-what will save you a lot of trouble, and maybe even keep you from burning out your pedals.
Lets start with most common jack and plug combination for 9VDC powered pedals, the barrel plug.
Barrel refers to its round (barrel) shape. You can see one plugged into a Mad Man pedal at the top of this blog. The size of the center pin (conductor) usually gives you a hint on what voltage the adapter is. A 2.1mm diameter center pin usually means 9VDC. Power connectors have different center pin sizes so you can’t (easily) plug non-matching plugs and jacks together and risk damaging the electronics with the wrong voltage. Besides 2.1mm, the most common barrel plug center pin sizes are 2.5mm and 3.5mm.
The center pin for effects pedal power is almost always ground.
For instance, Golden Path, Boss and Ibanez use center pin negative on power input jacks. This is contrary to most other 2.1mm barrel plugs on power adapters for household appliances. The reason for the reversal from the standard connector polarity is that it makes for a simple and inexpensive circuit to switch from battery to power adapter and to turn the power on when a guitar cable is inserted into the input jack of the pedal.
Always check on the back of the power supply to see what voltage it is and whether the center pin is positive or negative.
Not doing so can lead to pedal burn out. Check out this picture of a Boss PSA power adapter. I highlighted in red the voltage (9V) and the plug polarity (negative center pin). You can tell by the minus sign on the symbol going to the middle of the diagram. Match that with the picture of the Golden Path Mad Man pedal at the top of this blog. As you can see, it’s also center pin negative.
The Mad Man power jack accepts a 2.1mm barrel plug, which is what the BOSS PSA power adapter is. If you have a pedal with positive center pin but your power adapter is negative center pin, there are polarity-reversing cables available from Voodoo labs and many others.
Another more subtle polarity problem to watch for is mixing negative and positive circuit ground pedals on the same power supply.
The power jack may call for center pin negative, but inside the pedal the ground is not negative, but is positive instead. It’s not uncommon to have a positive ground in a Germanium Fuzz Tone, so be careful. You will create a short and possibly burn out your power supply. How does this happen? When you connect two pedals in a pedal chain to the same power supply, the grounds are connected in two ways; through the ground wire in the ¼” signal cable between them and through the ground in the power supply cables. If the ground on one pedal is positive it will short to the negative ground from the ¼” cable. Check the pedal manual to make sure.
A solution for all of these problems is to use independent power supplies for each pedal. That can be accomplished in a couple of different ways. Either use separate wall warts or a multi-output power supply in which the supplies are isolated. Multi-output power supplies that share the same ground for each power output will NOT work. A future blog will go into more detail on isolated power supplies.
In this blog post, we began to cover the basics of voltages, power plug polarities and power connector types. Next time I’ll continue on with this topic, going into higher voltage pedals, AC powered pedals and more connector types.
What does your guitar pedalboard power system look like? What collection of voltages, polarities and connector types have you dealt with? Comment below or send me a picture and a description. It’s OK if it doesn’t have Golden Path Pedals on it. – This is all about discovering new stuff along the path to perfect tone.