Stomp School: What's Inside Your Pedals?

Greetings, pedal stompers, and welcome back to Stomp School. It occurs to me that I might have lost a few of you in last month’s discussion of technologies such as surface-mounted devices (SMDs). I initially considered addressing this by following up with a lengthy dissertation on the history of surface-mount technology. Then I thought, “Wait a minute—I’m not an engineer, I’m a guitar player!” My interest in electronics and technology is mainly focused on how it relates to music gear, and I imagine the same is true for most of you. Obviously, there are a number of bona fide engineers among us, but most of us are not electronics wizards—and some of us are downright technophobic.

A subset of guitar-playing gear enthusiasts have a heavy interest in DIY stompboxes, and there’s plenty of info on the web that caters to them. But, based on my experience, along with feedback I’ve received on the column, most players aren’t inclined to pursue that degree of dedication and expertise in music electronics. Basically, we want as much information as will get us by. The question is, “What will get us by—and how and where do we find it?”

Fortunately, you don’t need an engineering degree to get a better understanding and appreciation of what makes your pedals tick. In fact, you can start right now by doing this: Grab the pedal closest to you, open it up, and take a look inside (you’ll probably have to get a Phillips-head screwdriver first). Why would you want to do this? Because it’s one of the best ways to become a more informed buyer. Even if you know nothing about electronics, it’s a habit that can eventually become very instructive. It can also help demystify a lot of what would otherwise be a bunch of marketing spiel. Think of it as reading the ingredients on a label in the grocery store instead of relying on a TV commercial for the product info.

The first thing I do when I get a pedal is pop it open and look inside. I think I’ve always done it. Curiosity gets the better of me and I can’t help it. It took a very long time, however, before I had the foggiest clue what I was looking at. I was at least able to discern such things as build quality and the number of little doohickeys on the circuit board, and that was usually well worth the five minutes it took to take a peek.

If you’ve never done it before and the idea makes you a little skittish, don’t worry. Unless you’re unusually clumsy or careless, you won’t hurt anything. And if it’s a regular 9-volt-battery- powered pedal, then there’s nothing in there that will hurt you. (Note: AC-powered gear is another story, and guitar amps often carry voltages that could potentially be lethal. Let’s just stick with pedals for now.)

The next best thing to looking inside a stompbox is to look at pictures of what we lovingly refer to as “pedal guts.” They say a picture is worth a thousand words, so rather than using a thousand words to describe what I mean, let’s look at the pictures below instead.



The first photo is of my beloved circa-’79 Ibanez TS-808 Tube Screamer, and inside it you can get a glimpse of traditional “through-hole” electronics on a single-sided printed circuit board (PCB). Here you can see most of the components found in the majority of guitar pedals. For the uninitiated, resistors are the green things with colored stripes that are standing on end, electrolytic capacitors are the tall lightand dark-blue cylinders, film capacitors are the big green and reddish-brown things that look like Chiclets gum, and transistors look like little black beans. If you look carefully, you can also see ceramic capacitors, a few diodes, and (hiding in the electronic underbrush) a Texas Instruments RC4558P IC chip.

The Electro-Harmonix POG2, on the other hand, is a cool pedal that incorporates digital signal-processing circuitry. It makes more sense to use SMDs in effects like this.

On the other end of the spectrum, you’ve got old-school devices like the above gut shot of a vintage Marshall Supa Fuzz, which proudly sports three Mullard OC75 germanium transistors. That’s hot!

It’s good to know what goes into making your tone. These pictures (along with your own research) should help provide a visual reference for our future discussions. With an open mind and enough willingness, you can easily learn enough to be informed without giving up all your valuable time to practice and play music. We’ll get more into various types of electronic components next time. Until then, keep on stompin’!