In researching my recent column on Altoids, those “curiously strong” mints in the nifty tin containers, I came across pictures of a miniature guitar amp housed in an Altoid tin, and learned that someone was selling kits to make them on Etsy.com.

Naturally, I had to have one. Not for myself, but for my daughter, who plays the electric guitar as a kind of warm-up before diving into her cello practice.

For the uninitiated: a guitar amp is the device that magnifies the puny signal created by strumming an electric guitar — an instrument whose solid body doesn’t resonate very much — and delivers it to a powered speaker, which then blasts the guitar signal at any volume you like, from loud-ish all the way up to ear-splitting.

A typical practice amp weighs about twenty-five pounds and looks like a small square suitcase, complete with a handle on top and little rubber feet, so you can imagine the appeal of an amp that fits in a pocket.

Of course, the smaller the speaker, the smaller the sound. We didn’t expect much of the 2” speaker that came with the kit. We were more interested in the headphone jack that would enable Nina to play her electric guitar VERY QUIETLY. Plugging in the headphones would disable the little speaker. The amplifier would deliver her rock and roll stylings directly to the headphones; future roommates would hear only the faint metallic strumming of the guitar itself.

The heart of the kit was a printed circuit board about the size of a credit card. To that, we were to solder various tiny components, including the miniature speaker; a snap connector for a 9v battery; a 1/4” jack for the guitar cable; a mini-jack for the headphones; a potentiometer switch for turning it on and adjusting the volume; and a handful of chips, capacitors, diodes, and resistors so small they looked like a heap of colorful midges.

The scale of the components was a rebuke to my aging eyes, but Nina wasn’t too bothered. We set up a soldering station on the dining room table, organized the parts, then off she went, threading the components’ delicate metal legs through the board and soldering them to the back.

The work went smoothly. The instructions were decent, and everything in the kit was well labeled. When she put down the soldering iron, the little amp looked just like the finished one in the picture. We attached a 9v battery, plugged in the guitar cable, and switched it on.

Nina strummed her guitar, and the tinny little speaker came to life. Even better, when we plugged in the headphones, the speaker went silent, just like it was supposed to.

Success!

There were still a few hurdles to overcome. In the course of mounting the amp in the Altoids tin, some of the solder joints cracked and had to be reflowed. We also discovered that we had to hold the circuit board by its edges; a stray finger on the back of the board was enough to complete some of the circuits and cause painfully loud feedback.

Lesson learned.

After we were done, I studied the schematic. I wanted to show it to Nina and explain the function of each component, and how they all added up to amplify her music. But I quickly realized an awful truth: I had no idea how a guitar amp worked!

“I’m going to look it up on the Internet,” I said. “I’ll be right back.”

Nina gave me a knowing look, then went back to the song she was practicing.

And that’s when I fell down the rabbit hole.

I started with the individual components: what, exactly, did a capacitor do? Or, for that matter, a diode?

How did a potentiometer change the volume?

Wikipedia was helpful, but each new thing I learned led to something else. Okay, so a capacitor acts as a kind of miniature battery, temporarily storing a charge. But how does that help enlarge the tiny guitar sound? Fine, I get that a diode only allows current to flow in one direction, but why is that important to this particular circuit?

The more I learned, the more I needed to learn. It bothered me not to know these things! What about the computer chip at the heart of the circuit? We talk about computer chips all the time. But how do they really work?

Learning about the chip led me to the history of transistors. The history of transistors led me to the technology of vacuum tubes.

Vacuum tubes? I always wondered how those things worked…

As I dug deeper and deeper, I turned to Youtube for help filling in some of the blanks. I wasn’t picky. Shaky camera work and amateur audio were fine, so long as I got the information I needed. Ultimately, I found a video by a hobbyist who rebuilds old Fender guitar amplifiers for fun.

It wasn’t the best lecture I’ve ever heard, but here was someone patiently explaining step by step, with pencil and paper — and occasional interruptions from his yapping corgi — how an old-school amplifier, complete with vacuum tubes, works its electronic magic on a guitar signal.

I looked up at the clock. Suddenly, it was time to make dinner. My eyes were bleary and my mind was whirling, but I had my answers.

Now all I had to do was find Nina. I hadn’t heard the cello for hours.