Power supplies

Got a sick deal on a Rolaha Sound Korgvas 5500, but it didn't come with a power supply?

Importing a unit from a different region, and worried about different mains voltage / frequency / sockets?

Your power supply broke?

Fear not, this is the page for you!

Units with DC power input

DC stands for "direct current" - meaning a device receives a constant, non-alternating load. Examples of DC power sources include typical AA and AAA batteries. Like with batteries, there is a positive and a negative terminal to any DC power supply.

USB bus power

If the unit is USB "bus powered", that means it's powered by the USB input. This makes everything simple. Note that there are also units that have USB ports but are not powered by USB. On those devices, the ports are for data only.

Barrel jack

The Roland SC-7 has a barrel jack.

Many devices accept low-voltage DC (direct current) power via a barrel jack. This means:

• The actual power supply is a separate unit, not part of the device itself.
• Only the power supply is tied to a specific type of mains AC power. The device itself is region-independent.
• If the power supply breaks or doesn't work in your region, you can just get another power supply that works for you.
• You aren't stuck with some failure-prone, inefficient old power supply. You can probably get a brand new one.

Barrel jacks are usually a common type that's used by several manufacturers. This means:

• You don't need an original Roland/Yamaha/whatever power supply. You can get one from any brand, just pay close attention to the specs.
• If it's more convenient, you can get a "universal" supply that will work for several types of barrel jack.

What makes a power supply compatible

Some sizes of barrel jacks

The easiest way to find a compatible power supply is to check the unit itself or the manual. Usually it'll say something like "USE ABC-123 ADAPTER ONLY". You don't have to listen to the manufacturer here, but if you can get that specific adapter, that's your problem solved. Otherwise…

There are four things you must get right for a DC power supply with a barrel jack, so that it works with your device:

• The voltage (in volts, symbol V). For example, 9V or 12V. This should exactly match. For example, only use a 9V supply for a 9V device.
• The amperage or current (in amps, symbol A). For example, 300mA (0.3A) or 500mA (0.5A). For this, the supply must provide at least as much as the device needs. So if the device needs 300mA and the supply provides 500mA, that's fine, but the reverse won't work.
• The size of the barrel jack. There's a few different shapes and sizes. This one is safe to mess up: if it doesn't fit, it doesn't fit.
• The polarity of the barrel jack. This is either:

• center/inside is negative (-), outside is positive (+)
• center/inside is positive (+), outside is negative (-)

If you see power given in watts (symbol W), that's the voltage multiplied by the amperage.

Be particularly careful with voltage and polarity. Getting those wrong may fry your device if it has no internal protection against it.

These four things should be marked on the power supply, and on the device. If they're not on the device itself, check the manual, or (for Yamaha products) find an image of the power supply the manufacturer suggested you use. But to save you the effort…

Table of power supply requirements

Manufacturer	Devices	Voltage	Polarity	Size
Roland	SC-7 (300mA)	9V	center negative	2.1mm
Yamaha	QY70, CBX-K1XG, PSR-350	12V	center positive	??mm

Units with AC power input

Units using AC (alternating current) for its power delivery typically have their power drawn directly from mains, and thus have a built-in transformer to convert the mains voltage to something more appropriate.

Hard-wired units

You can tell if a unit is hard-wired if you cannot disconnect the power lead from the device. An example of this is the Roland SC-88 PRO. Devices that are hard-wire are typically configured to only accept a voltage for a certain region - US devices accepting 120 volt, 60 hertz, EU/UK devices accepting 230-250 volt, 50 hertz, and so on. It is not enough to use a plug converter - for example, using an adapter to plug a 120v unit into a 250v outlet can at best damage the unit beyond repair, or at worst explode and start a fire.

Ways around this:

• Use a step-down or a step-up transformer, depending on where the device came from and where you're trying to use it (250v to 120v would be a step down, 120v to 250v would be a step up)
• Modify the power supply's intake to match what your outlets supply (for example, modifying a Japanese SC-88 PRO to use European 250v50hz loads by rewiring one lead in the transformer)

Kettle leads (3-pin) and Figure-8 leads (2-pin)

In some cases, a device leaves the power lead issue up to the user - these are sometimes hard-wired to a specific voltage inside the transformer, but may also sport universal voltage (in which any regional voltage or frequency combination is usable)

Kettle leads

• Kettle leads are the same cable typically used to power desktop computers with, or in some cases monitors. It's that 3-pin cable.
• Examples of this include the Roland XV-5080 and XV-5050.

Figure-8 leads

• Figure-8 leads are comparatively smaller by omitting the earth/ground found in some outlet standards, such as the UK. It sports 2 pins, and the female end looks like the number 8, hence the name.
• Examples of this include the Roland SC-8850.

Non-standard AC power inputs

Rarely you may encounter a device asking for an eccentric power input - Alesis synths are notorious as they require 9 volts AC and have a weird 4-pin DIN for the port.

TBD: format this better i don't know what i'm doing honestly. maybe even reword this. idk. yeah.