DIY USB PD power for HAPAX (including battery power!)

If you have a USB PD power supply or battery capable of outputting 15V at 18W and are comfortable with a little DIY, this is the post for you!


:warning: If you’re going to build this, please ensure you’ve got the polarity correct (center +), or you could possibly damage HAPAX. If you’re unsure, use a multimeter to test that the polarity is correct before using it with HAPAX. If you are unsure about any of this, find someone who can help you. I’m not responsible if you damage your HAPAX!


  • Not all USB C power sources support USB PD
  • Not all USB PD power sources will output 15V
  • The HAPAX power socket accepts a standard 5.5mm x 2.5mm jack, but the power source must be 15V 1.2A (18W) center +


  1. Program a YZXStudio ZYPDE USB PD adapter to negotiate 15V on startup (programming instructions below). [EDIT: see this post for a smaller, cheaper alternative that requires no programming, but does require soldering]

  2. Connect a 5.5mm x 2.5mm barrel jack cable like this one (I used one I already had, so I can’t tell you what the polarity is for that one) into the +/- terminals of the ZYPDE so that the center of the barrel jack is +

  3. Ensure the cable is 15V, center + with a multimeter!

  4. Heat shrink all the things if you’re fancy. If not, maybe wrap it in some electrical tape?

  5. Connect to HAPAX and enjoy your much improved lifestyle :mirror_ball: :notes: :sunglasses: :notes: :mirror_ball:

ZYPDE Programming Instructions

TL;DR: Hold the button when connecting power to the ZYPDE. The lights will flash in a rainbow color. Release the button. Now press (and release) the button a few times until the light is Cyan. You should be able to confirm that it’s outputting 15V. Now long-press the button to “lock in” 15V at startup. Verify by disconnecting and reconnecting the power.

Full programming instructions here

Final Note

Always connect the ZYPDE to your USB PD power source and ensure that the light is cyan (signifying 15V) before connecting the barrel jack to HAPAX. This will ensure that you don’t send the wrong voltage into HAPAX. If the color is anything other than cyan, it’s possible that your USB PD power source is not able to send 15V. In that case, try a different USB PD power source.


YZXStudio ZYPDE USB PD adapter

5.5mm x 2.5mm barrel jack cable

HAPAX adapter for reference, note that it’s 15V 1.2A (18W) Center +

My 15 VDC Center + USB PD adapter, complete with heat shrink tubing because I’m fancy

My HAPAX, running off of an Anker Power core+ 26800 PD battery pack with a super extra fancy power display cable


@Thibault_Squarp can you confirm if HAPAX has reverse-voltage protection, or if it will be able to handle 5V, 9V, 12V or 20V (all voltages that USB PD supports) if someone doesn’t follow my directions?

I just want to make sure people take my warnings seriously!

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There is reverse-voltage protection & over-voltage protection, so anything below 0V or above 15V should short circuit the power supply, and keep Hapax safe.
However, I don’t think there is under-voltage protection/detection, but I don’t think it will cause too much damage.

tl;dr: Shouldn’t be too dangerous, but try at your own risk.


Note that if you use a fixed 15V USB PD Decoy Trigger like this one, it’ll be smaller, cheaper, and you won’t have to worry about programming it. Here’s an example of a cable a made using a dedicated 9V USB PD Decoy Trigger, with a few breakout cables for powering pedals.

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Question: if we’re going to power the hapax from a powerbank with native 15v output we shouldn’t need the PD adapter, right?

In that case I guess it’s only down to match (or exceed) the minimum current draw of the Hapax (1.2A)

So we should be good with a straight usb->5.5x2.2 centre positive cable, right again?

AFAIK, there is no such thing as a “straight usb->5.5x2.2 centre positive cable” that provides 15V, because USB is always 5V unless you’re using some kind of device to negotiate a higher voltage from a USB PD or QC power source (like a USB PD decoy trigger).

You need a USB PD Decoy Trigger to get 15V out of a USB PD power source. There may be circuits to get 15V out of a USB QC (or some other USB) power source, but I don’t know of any.

And, of course, you should be able to power HAPAX, without any additional circuitry, from any non-USB power source that supplies 15V DC at the same or greater amperage / wattage (1.2A / 18W), that has a 5.5mm x 2.5mm barrel jack connector with center + polarity.

This are the specs of a random 65w powerbank on Amazon

And this is the kind of cable I was talking about

There are plenty similar, I guess there’s only to check the polarity

Edit: wrong cable picture

That is a USB PD Decoy Trigger cable. However, it’s outputting 18-20V DC, and not 15V DC.

I haven’t found a pre-made cable that outputs 15V DC with the correct size barrel connector and polarity, which is why I posted this guide.

I’m not sure if the one you linked will cause any problems with HAPAX, but per @Thibault_Squarp’s warning above, I wouldn’t recommend using it.

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Someone should ask MyVolts if they have one yet.

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A quick search of the myVolts website shows that they sell a 15V Ripcord USB to DC power cable, with a center positive 5.5x2.5mm adapter, but it’s only rated at 12W, which is significantly lower than the 18W that HAPAX’s power adapter provides.

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With this DIY cable allow me to power the Hapax directly from the USB-C ports on my M1 MBP?

I don’t have a Mac, so I can’t answer that. But if you do some research and learn that your Mac’s USB-C ports can provide 15V at 18W, it should work. Let us know what you find out :slight_smile:

Surprisingly (or unsurprisingly?) hard to find details, the best I could find was this which doesn’t look good: