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.

If your device has a DC power input, then:

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

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 (USB for data only).

Some notable DTM modules with bus power:

• Roland-ED SC-8820
• Edirol SD-20

Barrel jack

The Roland SC-7 has a barrel jack.

Many devices accept low-voltage DC power via a barrel jack. Barrel jacks are usually of a common type, so:

• 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 (e.g. this one) that works with most devices.

What makes a power supply compatible

Some sizes of barrel plugs

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 plug, 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. The plug can be a bit smaller than the hole, though it's better if you choose one you can't accidentally plug into the wrong device.
• 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.

The voltage, amperage and polarity should be clearly 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. As for the size of the jack and plug, that's more of a trial-and-error thing. But to save you all this effort…

Table of power supply requirements

Manufacturer	Devices	Voltage	Polarity	Size
Roland	SC-7 (300mA) SC-88VL (800mA) JV-1010 (430mA)	9V	center negative	??mm (2.1mm works, 2.5mm works)
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. Examples of hard-wired units:

• Roland SC-88
• 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)
• Obtain a closely related device that is not hard-wired instead. For example, the SC-88VL offers almost all the features of the SC-88, but uses a DC input instead. The SC-88ST and SC-88 Pro ST are other examples.

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). This varies from device to device and usually requires some research to find out the answer (hopefully we'll have them here soon)

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 the Alesis QuadraSynth keyboards (not modules).

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-ED SC-8850.

Non-standard AC power inputs

Rarely you may encounter a device asking for an eccentric power input - some Alesis units, such as the Quadrasynth modules will use a 4-pin 9 volt AC power input as opposed to a standard DC input, or AC input - 3rd party units will usually output 9V AC, rated to 2 amps. The keyboard versions, notably, use standard 3-pin kettle lead inputs directly from the wall. There's no other way around this really, you need to buy something directly compatible.

Another unusual example is the Roland TD-7, which takes 12V AC input, unlike the vast majority of other Roland sound modules, which take 9V DC input or standard mains voltage AC input.