1U Pedal Power

February 6, 2025

New Pedal Power Module #

I’m on a perpetual journey of taking as little gear with me to shows as possible. As a person running mostly simple little analog Eurorack modules, I’ve got power to spare in my case, so I’d like to be able to leverage that and leave the OneSpot at home for a couple of pedals I like to have around. I’ve also got a 1U row that’s too empty for my taste. As a result, I’ve got a 1U 4HP pedal power module under development now. It’ll be able to deliver up to 500mA of power out a standard-issue center negative guitar pedal power jack.

There are some inherent challenges in generating a not-too-noisy 9V rail off of 12V that’s also capable of delivering a decent amount of power. Mostly, a 3 volt drop across a linear regulator at 500mA is quite a lot of power and therefore heat to dissipate inside an already-warm Eurorack case. Of course I could use a switcher, but I’m being precious about the not-too-noisy requiremnet and switchers like to shout at light loads.

My solution here is to put a chonk of a series resistor in front of my linear regulator–that’s the tall boi in the middle of my board up above. At 500mA that resistor will drop just about 2V and burn up some of the heat that would’ve otherwise generated a little furnace in the regulator itself. The side benefit of the input resistor is that, in conjunction with my input capacitance at the regulator, I get a “free” low pass filter at the input which will help out the regulator’s internal power supply rejection ratio and spit out a nice clean 9V for any sort of pedal that might be hanging out next door.

I’m not entirely sure when I’ll wrap all this up, but hopefully in the next couple of weeks.