power supplies

In my June 2020 State of the Stomp, we talked about the evolution of pedal power, from the days of disposable batteries to integrated, isolated supplies. These were linear supplies equipped with large transformers, taking mains power, converting it, rectifying it, and regulating it to make noise-free-and-stable 9V outputs. However, over time batteries and the supplies designed to replace them went from being more than enough to woefully insufficient. How?

Let’s talk about battery capabilities. Batteries deliver energy with a specific potential (volts) and capacity (amps). Batteries can propel cars at ludicrous speeds or barely keep your wristwatch ticking. If you were to autopsy a typical 9V battery, you’d find six little 1.5 volt batteries inside, wired to make 9V at the battery terminals, ensuring your favorite effect has enough electrical headroom to function. Unfortunately, those tiny batteries don’t hold much energy and can’t deliver that energy at high rates. This means they do well powering a fuzz that draws little current (~1 mA), but as guitar effects became more power hungry, the venerable 9V and the linear power supplies that mimicked them were outstripped. An arms race between pedal effects manufacturers and power-supply makers had begun.

The advent of digital signal processing (DSP) quickly caused an increase in the power requirements of effects. The first guitar DSP products drew whatever they needed from their own 120 VAC mains power supplies. Refrigerator-sized collections of primordial digital reverbs and delays consumed enough power to spin electric meters wildly and dim every light bulb on the block. Companies like Roland/Boss eventually made digital delays that drew less than 100 mA from a 9V battery, putting DSP at your feet! While many players were content to stomp on these little marvels, others wanted more—more features, more functions, more algorithms, more power.

Companies like Line 6 started making effects that weren’t just one effect but modeled many effects and did so with more fidelity than had been previously available in digital stompboxes. Internally, these devices had complicated power subsystems of their own, powering analog circuits, processors, memories, and converters. A 9V battery’s capacity just couldn’t cut it. Companies like Voodoo Lab modified existing power products to appease these power pigs. They even labeled ports “L6,” identifying the responsible party. Things were peaceful for a period, but others developed effects with voracious power budgets. Eventide released their Factor pedals, and while available integrated supplies could power one of them, their introduction heralded that power supplies were coming up short. Pedals with high current needs became ubiquitous. High-wattage pedals from Line 6, Eventide, and Strymon began to show up in multiples on single boards. To cope with a marketplace dominated by linear supplies that weren’t totally ready for them, these high-power effects started shipping with their own switch-mode-style supplies.

The “switch” in switch mode comes from the switching transistors that chop the wall voltage at high speed to make use of smaller components at higher efficiencies. While smaller and more efficient means big power in small packages, switch mode has a bad rap with some, due, in part, to its typical noisy performance. Since consumer products are often built to a price, and designers may not prioritize noise performance to save cost, many output a DC voltage with switching-related noise tagging along for the ride. Power supply companies like Truetone and Strymon got clever and mashed together the benefits of switch mode and linear supplies. These internal switch mode supplies do the heavy lifting, and their outputs are polished up with a linear regulator. Almost every integrated supply company has moved or is moving to these hybrid supplies, because we’ve demanded the power outputs of highly efficient switch-mode supplies with noise performance like old-school linear supplies and batteries. With both terms met, there is peace again on our pedalboards.

It’s easy to take for granted the amount of innovation required to have as much fun as we do playing music. Whether it’s flashy effects or the modest supplies that keep them twinkling, an army of engineers and artists has been working for decades, keeping us in marvelous technologies that ultimately go unsung as we sing the songs they helped create.