I got into electronics because I was too poor to afford the guitar effects pedals I wanted, so I set out to build my own. My intro book was Craig Anderton's "Electronics Projects for Musicians".
From there, an indespensible resource in my education was diystompboxes.com/smfforum (DIY electronics forum). Focus is on guitar effects, but there are people making amps, guitars, hi-fi, and digital gear as well. The community there has an excellent core of helpful veteran DIYers and engineers, and a strong culture of sharing and teaching.
The humble Fuzz Face is generally a "beginner" level project which you can get working in an afternoon, yet if you drill down into why it works you've got enough to chew on to fill 2 or 3 college courses (at least 1 of those being a "weed out" level course). This pedal was a staple of Jimi Hendrix, but he had a good ear and legend says he'd sort through boxes of them to find the good ones, because they varied a lot.
The reason they varied is because they were built around germanium transistors, which were low tolerance parts. And the circuit itself is really high gain and temperature sensitive and has all sorts of caveats around it.
So if you covet that Jimi Hendrix-quality Fuzz Face sound, you need to deep dive into things like measuring hFE and keeping wiring clean around high-gain circuits to keep from turning it into an oscillator (or a radio). There are numerous rabbit holes to explore, like "do old school resistors sound better?" or "what if I want to power it from a normal +9V power supply instead of a battery?"
Then you realize that turning the guitar's volume knob down causes the Fuzz Face to totally change character from racous fuzz into something like a Brian May-esque treble boost, and why the heck does that happen? It's because the input to the Fuzz is a low impedance relative to the guitar, and causes the (mostly inductive) guitar pickup to be heavily loaded at high frequencies, making the distortion smoother than it would otherwise be. So the guitar itself is part of the circuit, and inserting an active circuit (like another pedal) between the guitar and the Fuzz Face ruins everything!
So I guess my point is don't go into it with the generic goal of "learn electronics", instead have a specific goal like "make the best Hi-Fi system possible for my living room, for under $2000" or "make a quadcopter from scratch". Eventually you'll accumulate a ton of depth in a specific domain that you really care about, and you'll pick up general concepts along the way.
From there, an indespensible resource in my education was diystompboxes.com/smfforum (DIY electronics forum). Focus is on guitar effects, but there are people making amps, guitars, hi-fi, and digital gear as well. The community there has an excellent core of helpful veteran DIYers and engineers, and a strong culture of sharing and teaching.
The humble Fuzz Face is generally a "beginner" level project which you can get working in an afternoon, yet if you drill down into why it works you've got enough to chew on to fill 2 or 3 college courses (at least 1 of those being a "weed out" level course). This pedal was a staple of Jimi Hendrix, but he had a good ear and legend says he'd sort through boxes of them to find the good ones, because they varied a lot. The reason they varied is because they were built around germanium transistors, which were low tolerance parts. And the circuit itself is really high gain and temperature sensitive and has all sorts of caveats around it.
So if you covet that Jimi Hendrix-quality Fuzz Face sound, you need to deep dive into things like measuring hFE and keeping wiring clean around high-gain circuits to keep from turning it into an oscillator (or a radio). There are numerous rabbit holes to explore, like "do old school resistors sound better?" or "what if I want to power it from a normal +9V power supply instead of a battery?"
Then you realize that turning the guitar's volume knob down causes the Fuzz Face to totally change character from racous fuzz into something like a Brian May-esque treble boost, and why the heck does that happen? It's because the input to the Fuzz is a low impedance relative to the guitar, and causes the (mostly inductive) guitar pickup to be heavily loaded at high frequencies, making the distortion smoother than it would otherwise be. So the guitar itself is part of the circuit, and inserting an active circuit (like another pedal) between the guitar and the Fuzz Face ruins everything!
So I guess my point is don't go into it with the generic goal of "learn electronics", instead have a specific goal like "make the best Hi-Fi system possible for my living room, for under $2000" or "make a quadcopter from scratch". Eventually you'll accumulate a ton of depth in a specific domain that you really care about, and you'll pick up general concepts along the way.