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<header class="topbar"><div class="brand">◈ AMP LAB / 01</div><nav class="nav"><a href="#parts">Parts</a><a href="#schematics">Schematics</a><a href="#build">Build</a><a href="#test">Test</a></nav></header>
<main>
<section class="hero"><div><div class="kicker">Practical electronics / beginner build</div><h1>Build a <span>stereo</span><br>amp on a breadboard.</h1><p>A pin-by-pin guide to two LM386 audio power amplifier channels. Turn a phone-level signal into room-filling sound while learning how power, gain, coupling, and grounding fit together.</p></div><aside class="hero-card"><div class="kicker">Signal monitor</div><h3>LEFT + RIGHT / LOW-VOLTAGE OUTPUT</h3><div class="meter"><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i></div><small>Designed for a 5–9 V supply · 8 Ω loads</small></aside></section>
<section class="section"><div class="section-head"><div><h2>01 / Start safe</h2><p class="section-intro">Low voltage does not mean no risk. Read the rails twice before applying power.</p></div></div><div class="notice"><strong>Safety first:</strong> use only an isolated 5–9 V DC source. Never connect to mains. Power off before changing wires; a polarized capacitor installed backwards may vent or fail.</div><div class="grid"><article class="card"><div class="icon">◎</div><h3>Workbench</h3><p>Eye protection, tidy leads, good lighting, and a nonconductive surface. Soldering is optional—this is breadboard-first.</p></article><article class="card"><div class="icon">⌁</div><h3>Tools</h3><p>Multimeter, wire cutters/strippers, jumper wires, phone or signal source, and two 8 Ω speakers.</p></article><article class="card"><div class="icon">◌</div><h3>Know the basics</h3><p>Rows of five breadboard holes connect internally. Capacitors marked + are polarized. Pin 1 is identified by the IC notch or dot.</p></article></div></section>
<section class="section" id="parts"><div class="section-head"><div><h2>02 / Bill of materials</h2><p class="section-intro">Buy two identical channels. LM386 is a single amplifier, so one chip handles each speaker.</p></div></div><table class="parts"><thead><tr><th>Component / part number</th><th>Qty</th><th>Purpose / role</th></tr></thead><tbody><tr><td>LM386N-1 low-voltage audio power amplifier IC</td><td>2</td><td>One amplifier channel per IC; internal gain 20.</td></tr><tr><td>10 µF electrolytic capacitor</td><td>2</td><td>Input coupling; blocks DC from the source.</td></tr><tr><td>220 µF electrolytic capacitor</td><td>2</td><td>Output coupling to each speaker.</td></tr><tr><td>100 nF ceramic + 100 µF electrolytic</td><td>2 each</td><td>High/low-frequency supply decoupling.</td></tr><tr><td>10 kΩ audio-taper potentiometer</td><td>2</td><td>Independent left/right volume.</td></tr><tr><td>8 Ω, 0.5–1 W speakers</td><td>2</td><td>Left and right loads.</td></tr><tr><td>5–9 V regulated supply or 9 V battery + clip</td><td>1</td><td>Clean, isolated power.</td></tr><tr><td>Solderless breadboard + jumper wire kit</td><td>1 each</td><td>Prototyping platform and connections.</td></tr><tr><td>Optional 10 nF capacitor + 1 kΩ resistor</td><td>2 each</td><td>Zobel stability network from output to ground.</td></tr></tbody></table></section>
<section class="section" id="schematics"><div class="section-head"><div><h2>03 / Read the circuit</h2><p class="section-intro">Build the right channel, then duplicate it for left. Ground is common; signal paths stay separate.</p></div></div><div class="diagram"><svg viewBox="0 0 1000 390" role="img" aria-label="stereo LM386 schematic"><defs><style>.w{stroke:#55d6ff;stroke-width:3;fill:none}.p{stroke:#ffc857;stroke-width:3;fill:none}.g{stroke:#7ee2a8;stroke-width:3;fill:none}.t{fill:#e8f0fa;font:15px system-ui}.s{fill:#9bb0c8;font:12px system-ui}.chip{fill:#12243a;stroke:#55d6ff;stroke-width:2}</style></defs><text x="20" y="25" class="t">LEFT CHANNEL</text><text x="515" y="25" class="t">RIGHT CHANNEL</text><g transform="translate(20 45)"><rect class="chip" x="280" y="90" width="135" height="140" rx="8"/><text class="t" x="315" y="165">LM386</text><path class="w" d="M0 125h280M415 160h80l35 0"/><path class="p" d="M350 90V25H220"/><path class="g" d="M350 230v45H220m130 0h150"/><path class="p" d="M530 160v-45h55"/><path class="g" d="M575 160v65h-45"/><path class="w" d="M575 160h65v45"/><text class="s" x="4" y="119">L IN → 10µF → pin 3</text><text class="s" x="220" y="20">+5–9V → pin 6</text><text class="s" x="270" y="300">pin 4 → common GND</text><text class="s" x="535" y="108">220µF +</text><text class="s" x="625" y="155">8Ω SPK</text><text class="s" x="5" y="175">pin 2 → GND</text></g><g transform="translate(510 45)"><rect class="chip" x="280" y="90" width="135" height="140" rx="8"/><text class="t" x="315" y="165">LM386</text><path class="w" d="M0 125h280M415 160h80l35 0"/><path class="p" d="M350 90V25H220"/><path class="g" d="M350 230v45H220m130 0h150"/><path class="p" d="M530 160v-45h55"/><path class="g" d="M575 160v65h-45"/><path class="w" d="M575 160h65v45"/><text class="s" x="4" y="119">R IN → 10µF → pin 3</text><text class="s" x="220" y="20">+5–9V → pin 6</text><text class="s" x="270" y="300">pin 4 → common GND</text><text class="s" x="535" y="108">220µF +</text><text class="s" x="625" y="155">8Ω SPK</text><text class="s" x="5" y="175">pin 2 → GND</text></g></svg><p class="diagram-caption"><span style="color:var(--cyan)">Cyan = signal</span> · <span style="color:var(--amber)">amber = +V</span> · <span style="color:var(--green)">green = ground</span>. Pin 5 is output; pin 6 +V; pin 4 ground. Leave pins 1 and 8 open for gain 20.</p></div><div class="diagram" style="margin-top:18px"><svg viewBox="0 0 1000 285" role="img" aria-label="breadboard wiring map"><defs><style>.r{fill:#162b43;stroke:#385a78;stroke-width:2}.i{fill:#0b111b;stroke:#55d6ff;stroke-width:2}.a{stroke:#ffc857;stroke-width:4}.c{stroke:#55d6ff;stroke-width:4}.n{stroke:#7ee2a8;stroke-width:4}.t{fill:#e8f0fa;font:14px system-ui}.s{fill:#9bb0c8;font:12px system-ui}</style></defs><text class="t" x="20" y="23">ONE CHANNEL · mirror for the second channel</text><rect class="r" x="25" y="50" width="950" height="32" rx="5"/><rect class="r" x="25" y="225" width="950" height="32" rx="5"/><text class="s" x="42" y="71">RED RAIL +5–9V</text><text class="s" x="42" y="246">BLUE RAIL 0V / GND</text><rect class="i" x="385" y="105" width="210" height="65" rx="7"/><path d="M490 105v65" stroke="#55d6ff" stroke-dasharray="4 4"/><text class="t" x="448" y="138">LM386</text><text class="s" x="420" y="157">center trench / notch ↑</text><path class="a" d="M410 105V66M570 170v71M490 105V66"/><path class="n" d="M430 170v71M550 170v71"/><path class="c" d="M385 122H230M595 145H760"/><text class="s" x="55" y="120">pot wiper → 10µF → pin 3</text><text class="s" x="765" y="149">pin 5 → 220µF → speaker +</text><text class="s" x="390" y="195">pins 2, 4 → GND rail</text><text class="s" x="740" y="215">speaker − → GND</text></svg><p class="diagram-caption">Each five-hole strip is connected internally; the center trench isolates IC sides. Keep input wire away from output wire.</p></div></section>
<section class="section" id="build"><div class="section-head"><div><h2>04 / Assemble, in order</h2><p class="section-intro">Unplug the battery while wiring. Complete and test one channel, then copy it.</p></div></div><div class="steps"><article class="step"><div><h3>Place the IC</h3><p>Bridge the center trench. With the notch up, pins number counter-clockwise: left side 1–4 top-to-bottom, right side 5–8 bottom-to-top. Verify your exact package datasheet.</p><code class="pinmap">1 GAIN · 2 IN− · 3 IN+ · 4 GND · 5 OUT · 6 VS · 7 BYPASS · 8 GAIN</code></div></article><article class="step"><div><h3>Establish rails and decouple</h3><p>Connect red battery lead to + rail and black to blue only at the end. Pin 6 → +V; pin 4 → GND. Place 100 nF ceramic and 100 µF electrolytic directly between rails, with electrolytic + to +V. Tie both channels to common rails.</p></div></article><article class="step"><div><h3>Add volume and input</h3><p>Each 10 kΩ pot: outer lug to source signal, other outer lug to GND, wiper to the positive leg of 10 µF. Capacitor negative → pin 3. Audio jack sleeve → GND; tip = left, ring = right. Mono source may feed both pots.</p></div></article><article class="step"><div><h3>Wire output</h3><p>Pin 5 → positive leg of 220 µF; negative leg → speaker +. Speaker − → common GND. Leave pins 1, 7, and 8 open. Optional stability: pin 5 → 10 nF → 1 kΩ → GND.</p></div></article><article class="step"><div><h3>Inspect, then power</h3><p>Turn both pots fully counter-clockwise. Check rail shorts, capacitor polarity, IC orientation, and one common ground. Connect battery, start source volume low, then raise slowly.</p></div></article></div></section>
<section class="section" id="test"><div class="section-head"><div><h2>05 / Test & troubleshoot</h2><p class="section-intro">A multimeter and a methodical pause beat guesswork. Disconnect power before moving a jumper.</p></div></div><div class="checks"><article class="card"><h3>✓ Before power</h3><p>Continuity-check ground. With power disconnected, verify red-to-blue is not a dead short. Confirm pin 6 → +V and pin 4 → GND. Inspect every polarized capacitor.</p></article><article class="card warn"><h3>! No sound / hum</h3><p>Check source ground, pot ground, pin 4, and speaker returns. Verify tip/ring and that the wiper, not an outer lug, feeds the capacitor.</p></article><article class="card warn"><h3>! Distortion or heat</h3><p>Lower source volume. Check 8 Ω impedance, reversed electrolytics, and output-to-input contact. Never connect a speaker directly to pin 5 without 220 µF coupling.</p></article><article class="card"><h3>✓ Voltage sanity check</h3><p>Powered with no audio, measure pin 6 to pin 4: 5–9 V. Pin 5 should sit near half the supply DC; near 0 V or +V means power down and inspect.</p></article></div><div class="notice"><strong>Feedback loop warning:</strong> keep speaker wires and pin 5 away from input wiring. If it squeals, power down, shorten leads, add the Zobel, and separate input/output routes.</div></section>
</main><footer class="footer">AMP LAB 01 · Low-voltage educational prototype · Verify pinouts against the datasheet for your exact LM386 package.</footer>`;
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