C.<p>This will be slightly <a href="https://mindly.social/tags/geeky" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>geeky</span></a>, and probably only of interest to <a href="https://mindly.social/tags/electronics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronics</span></a> hobbyists and <a href="https://mindly.social/tags/guitar" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>guitar</span></a> players. I happen to sit in the intersection of that particular <a href="https://mindly.social/tags/Venn" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Venn</span></a> diagram.</p><p>When I was a teenager, having only been playing guitar for a few years, I owned a guitar <a href="https://mindly.social/tags/effects" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>effects</span></a> pedal that went on to become legendary - the Boss HM-2 "Heavy Metal" <a href="https://mindly.social/tags/pedal" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>pedal</span></a>. Its sound is still ubiquitous in metal.</p><p>I don't have it any more. I think I traded it for an analog chorus, which was a seriously expensive pedal back then. Although I have other <a href="https://mindly.social/tags/distortion" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>distortion</span></a> effects, I've missed it a lot over the years.</p><p>Well, lots of hobbyists build their own effects. And the circuit schematics for many effects, particularly the classics, are available online. So like many others, I decided to build my own HM-2.</p><p>This image is the schematic for the <a href="https://mindly.social/tags/HM2" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>HM2</span></a>. It's not the most complicated pedal, but it's a league above something like an Ibanez Tube Screamer. As far as active devices go, it's got 6 <a href="https://mindly.social/tags/opamps" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>opamps</span></a> and 10 <a href="https://mindly.social/tags/transistors" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>transistors</span></a> of various types, along with a bunch of diodes for multiple types and stages of clipping, and the usual jumble of capacitors and resistors. Oh, and four potentiometers.</p><p>1/x</p><p><a href="https://mindly.social/tags/EffectPedal" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>EffectPedal</span></a> <a href="https://mindly.social/tags/HeavyMetal" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>HeavyMetal</span></a> <a href="https://mindly.social/tags/pedals" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>pedals</span></a> <a href="https://mindly.social/tags/metal" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>metal</span></a> <a href="https://mindly.social/tags/DIY" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>DIY</span></a> <a href="https://mindly.social/tags/schematic" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>schematic</span></a> <a href="https://mindly.social/tags/circuit" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>circuit</span></a> <a href="https://mindly.social/tags/hobby" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hobby</span></a> <a href="https://mindly.social/tags/OperationalAmplifier" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>OperationalAmplifier</span></a> <a href="https://mindly.social/tags/TubeScreamer" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>TubeScreamer</span></a></p>