Measure your pedals’ current draw

Do you have a pedal that isn’t in the ”Power List”, and you want to know how much power it consumes? Assuming it is a battery-powered pedal, measuring it is easy – all you need is a multimeter, a 9v battery and a patch cable. Oh, and the pedal, of course. 🙂

Unplug the battery connector and put it back on sideways, so only the negative (-) pole is connected. Plug a cable into the input jack to make sure the pedal will be powered up. Then measure (multimeter set to DC amperes, 100-200 mA) between the open battery pole and the open receptor in the connector. Use the multimeters’ red wire on the battery positive, and the black wire on the connector. The reading you get is the pedal’s current draw in resting/bypass mode. If it has an MXR-style mechanical switch, you can of course click the pedal on to get the ”active” mode current draw, if you like.

If you want to get the ”active” reading on a pedal with electronic Boss/Ibanez type bypass, things are slightly more tricky. With the measuring probes still on the battery/receptor, click the switch to put the pedal in ”active” mode. The trick is to not let the measuring probes lose contact – that will cause the pedal to shut off, and when it receives power again, it will be back in ”bypass” mode.

The giant hand (it’s not that big IRL, I promise!) is slightly obscuring the negative/black probe, but it is positioned on the connector in the battery clip. It’s pinched between my thumb and index finger, basically. I had to hold both probes in one hand to operate the camera with the other. Normally, you’d use one probe in each hand… You don’t have to input any signal, as most pedals draw full power as soon as they turn on. This particular pedal draws 8.12mA when active, and slightly less (just under 7mA) in bypass. Not a huge difference, thus, and I’d probably only report the higher figure.

Anyway – that’s it. Now go measure, and while you’re at it, help populate the list! E-mail me the results on andreas (at) stinkfoot.se or leave your figures as a comment on the main ”about the power list” page.

Wait – my pedal doesn’t run on a battery. What to do?

This one is a bit trickier, I must admit. The principle is the same – the multimeter needs to go inline with the power supply feed – but hacking it in is much more troublesome. Unless you are ready to cut your power supply cable apart, of course (please don’t). I made a special cable for this purpose, and of course you can do the same. Basically, it has a female jack the adapter plugs into, and a male plug that plugs into the pedal. I’ve left one of the conductors open at the female end, which means I have a point to insert the multimeter. Click the pic to the right for a bigger view.

You need:

  • 1 female 5.5×2.1mm jack
  • 1 male 5.5×2.1mm or 5.5×2.5mm plug (the latter will fit pedals that use that size jack as well)
  • A bit of 2-conductor cable (doesn’t have to be coaxial or shielded)

I’d suggest using a 2.1mm female jack/plug for plugging the power supply into, and a 2.5mm male plug for the pedal end. That way, the cable can be used with pedals that have a regular type (Boss style 2.1mm) jack, as well as those that have a 2.5mm jack (Whammy, Line 6 xx-4 series etc). A 2.5mm power supply plug will work with a 2.1mm female jack, although you might have to wiggle it slightly to make sure it connects properly. And the same obviously goes for the pedal end.

Um, that’s it. Keep track of which wire goes where (so you keep the center/sleeve configuration the same) and leave one wire open at one end. I used a female chassis jack, but you can just as well use a cable jack (make sure the open wire is long enough to allow you to route it out through the  plastic jacket). It doesn’t matter if you leave the center or sleeve wire open – if you get a negative mA reading, just flip the black and red multimeter probes.