Circuit
Qwen 3.6 27b MTP · full

Reviews & generation details
Reviews
No human review yet. Unreviewed does not mean unsuccessful.
Generation context
Imported historical artifact. Its exact original instructions and lineage are not known.
Generation prompt · exact text unavailable
See the current prompt for reference. It may differ from the instructions used to generate this artifact.
Inspect original source 70,023 bytes · SHA-256 a6ba0943e028
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Stereo Audio Amplifier — Breadboard Build Guide</title>
<style>
/* ── Reset & Base ─────────────────────────────── */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
--bg:#0d1117;--surface:#161b22;--card:#1c2333;--border:#30363d;
--text:#e6edf3;--muted:#8b949e;--accent:#58a6ff;--green:#3fb950;
--red:#f85149;--orange:#d29922;--purple:#bc8cff;--cyan:#39d2c0;
--mono:'Courier New',Consolas,monospace;
}
html{scroll-behavior:smooth;font-size:16px}
body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Helvetica,Arial,sans-serif;background:var(--bg);color:var(--text);line-height:1.7;padding:0}
/* ── Layout ───────────────────────────────────── */
.container{max-width:960px;margin:0 auto;padding:2rem 1.5rem}
header.hero{text-align:center;padding:3rem 1rem 2rem;background:linear-gradient(180deg,#161b22 0%,var(--bg) 100%);border-bottom:1px solid var(--border)}
header.hero h1{font-size:clamp(1.8rem,5vw,3rem);font-weight:800;letter-spacing:-.02em;background:linear-gradient(135deg,var(--accent),var(--cyan));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
header.hero .subtitle{color:var(--muted);font-size:1.1rem;margin-top:.5rem;max-width:600px;margin-inline:auto}
/* ── Navigation ───────────────────────────────── */
nav.toc{position:sticky;top:0;z-index:10;background:rgba(13,17,23,.92);backdrop-filter:blur(8px);border-bottom:1px solid var(--border);padding:.75rem 0}
nav.toc ol{display:flex;flex-wrap:wrap;justify-content:center;gap:.25rem 1rem;list-style:none;padding:0;margin:0}
nav.toc a{color:var(--muted);text-decoration:none;font-size:.85rem;padding:.3rem .6rem;border-radius:4px;transition:.2s}
nav.toc a:hover{color:var(--accent);background:rgba(88,166,255,.08)}
/* ── Sections ─────────────────────────────────── */
section{margin:3rem 0;padding-top:1.5rem}
section h2{font-size:1.6rem;font-weight:700;margin-bottom:1rem;padding-left:.75rem;border-left:4px solid var(--accent);color:#fff}
section h3{font-size:1.15rem;color:var(--cyan);margin:1.5rem 0 .75rem}
p{margin-bottom:1rem;color:var(--text)}
/* ── Cards & Boxes ────────────────────────────── */
.card{background:var(--card);border:1px solid var(--border);border-radius:8px;padding:1.25rem;margin-bottom:1.25rem}
.callout{padding:1rem 1.25rem;border-radius:6px;font-size:.93rem;margin:1rem 0;border-left:4px solid}
.callout.warn{background:rgba(210,153,34,.08);border-color:var(--orange)}
.callout.danger{background:rgba(248,81,73,.08);border-color:var(--red)}
.callout.info{background:rgba(88,166,255,.08);border-color:var(--accent)}
.callout.success{background:rgba(63,185,80,.08);border-color:var(--green)}
/* ── Tables ───────────────────────────────────── */
table.bom{width:100%;border-collapse:collapse;font-size:.9rem;margin:1rem 0}
table.bom th{text-align:left;padding:.65rem .75rem;background:#21262d;color:var(--accent);font-weight:600;border-bottom:2px solid var(--border)}
table.bom td{padding:.55rem .75rem;border-bottom:1px solid var(--border);color:var(--text)}
table.bom tr:hover td{background:rgba(88,166,255,.04)}
table.bom .qty{text-align:center;width:60px}
/* ── Steps ─────────────────────────────────────── */
.step{display:flex;gap:1rem;margin-bottom:1.5rem;align-items:flex-start}
.step-num{flex-shrink:0;width:36px;height:36px;border-radius:50%;background:var(--accent);color:#000;font-weight:800;display:flex;align-items:center;justify-content:center;font-size:.9rem;margin-top:.15rem}
.step-body h4{font-size:1.05rem;color:#fff;margin-bottom:.3rem}
.step-body p{margin-bottom:.5rem;color:var(--muted)}
/* ── SVG Diagrams ─────────────────────────────── */
.diagram-wrap{text-align:center;margin:1.5rem 0;overflow-x:auto;padding:1rem;background:#0f1923;border-radius:8px;border:1px solid var(--border)}
.diagram-wrap svg{max-width:100%;height:auto}
/* ── Pinout Table ─────────────────────────────── */
.pin-table{width:100%;border-collapse:collapse;font-size:.85rem;margin:1rem 0}
.pin-table th{background:#21262d;padding:.5rem .75rem;text-align:left;color:var(--accent);font-weight:600;border-bottom:2px solid var(--border)}
.pin-table td{padding:.45rem .75rem;border-bottom:1px solid var(--border)}
/* ── Troubleshooting List ─────────────────────── */
.trouble-item{margin-bottom:1.25rem;padding:1rem;background:var(--card);border-radius:6px;border-left:3px solid var(--orange)}
.trouble-item h4{color:var(--red);font-size:.95rem;margin-bottom:.3rem}
.trouble-item p{color:var(--muted);margin:0;font-size:.9rem}
/* ── Footer ───────────────────────────────────── */
footer{text-align:center;padding:2rem;color:var(--muted);font-size:.8rem;border-top:1px solid var(--border);margin-top:3rem}
/* ── Responsive ───────────────────────────────── */
@media(max-width:640px){
.container{padding:1rem}
nav.toc ol{gap:.25rem .5rem}
table.bom{font-size:.8rem}
.step{flex-direction:column;gap:.5rem}
}
/* ── Print ─────────────────────────────────────── */
@media print{body{background:#fff;color:#000}.container{max-width:100%}}
</style>
</head>
<body>
<!-- ═══════════════ HEADER ═══════════════ -->
<header class="hero">
<div style="font-size:3rem;margin-bottom:.5rem">🔊</div>
<h1>Stereo Audio Amplifier<br>Breadboard Build Guide</h1>
<p class="subtitle">Build a dual-channel audio amplifier from scratch using two LM386 ICs — no soldering required. A complete beginner-friendly guide with schematics, parts list, and step-by-step assembly.</p>
</header>
<!-- ═══════════════ NAVIGATION ═══════════════ -->
<nav class="toc">
<div class="container" style="padding-top:.5rem;padding-bottom:.5rem">
<ol>
<li><a href="#intro">Introduction</a></li>
<li><a href="#safety">Safety & Prerequisites</a></li>
<li><a href="#parts">Parts List</a></li>
<li><a href="#schematic">Schematic Diagram</a></li>
<li><a href="#breadboard">Breadboard Layout</a></li>
<li><a href="#assembly">Assembly Steps</a></li>
<li><a href="#testing">Testing & Troubleshooting</a></li>
</ol>
</div>
</nav>
<div class="container">
<!-- ═══════════════ SECTION 1: INTRODUCTION ═══════════════ -->
<section id="intro">
<h2>Introduction</h2>
<p>An audio amplifier takes a weak electrical signal — from your phone, MP3 player, or computer — and boosts it enough to drive speakers. At its heart is an <strong>operational amplifier (op-amp)</strong> or dedicated audio power IC that increases the voltage and current of the input waveform without distorting it.</p>
<p>This guide walks you through building a <strong>dual-channel stereo amplifier</strong> using two <strong>LM386 Low Voltage Audio Power Amplifier</strong> integrated circuits. The LM386 is legendary among hobbyists: it runs on as little as 4 V, delivers up to 325 mW into an 8 Ω speaker, and requires only a handful of external components.</p>
<div class="card">
<h3 style="margin-top:0">What You'll Build</h3>
<ul style="padding-left:1.2rem;color:var(--muted)">
<li>A fully functional <strong>stereo amplifier</strong> with independent left and right channels.</li>
<li><strong>Adjustable gain</strong> from 20× (minimum) to 200× (maximum) per channel via a capacitor between pins 1 & 8 on each LM386.</li>
<li><strong>Volume control</strong> on each channel using a dual-gang potentiometer.</li>
<li>A circuit that runs from a simple <strong>9 V battery or DC power supply</strong>.</li>
</ul>
</div>
<h3>How the LM386 Works</h3>
<p>The LM386 is a class-AB audio amplifier IC in an 8-pin DIP package. Internally it contains differential input stages, a gain-setting network, and a push-pull output stage. Key features:</p>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:1rem">
<li><strong>Pins 2 & 3</strong> — Inverting (−) and non-inverting (+) inputs.</li>
<li><strong>Pins 1 & 8</strong> — Gain-setting terminals. Open = gain of 20×. Add a 10 µF capacitor between them for gain of 200×.</li>
<li><strong>Pin 5</strong> — Output (connects to speaker via coupling capacitor).</li>
<li><strong>Pin 4</strong> — Ground.</li>
<li><strong>Pin 7</strong> — Positive supply voltage (V<sub>CC</sub>, typically 6–15 V).</li>
<li><strong>Pin 6</strong> — Bypass capacitor terminal (improves transient response; connect a 20 µF cap to ground).</li>
</ul>
<div class="callout info">
<strong>💡 Why two LM386s?</strong> A single LM386 handles one audio channel. For stereo (left + right), we use two ICs — each amplifying its own mono signal independently, producing true stereo output to a pair of speakers.
</div>
</section>
<!-- ═══════════════ SECTION 2: SAFETY & PREREQUISITES ═══════════════ -->
<section id="safety">
<h2>Safety & Prerequisites</h2>
<div class="callout danger">
<strong>⚠️ Safety First</strong><br>
Even though this circuit runs at low voltage (9 V DC), always follow good workbench practices. Never connect speakers directly to the IC output without a coupling capacitor — it can damage both the speaker and the LM386. Double-check all connections before applying power.
</div>
<h3>Workbench Safety Rules</h3>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:1.5rem">
<li><strong>Power off first.</strong> Always disconnect the power supply before making or changing connections on the breadboard.</li>
<li><strong>Check polarity.</strong> Electrolytic capacitors are polarized — reverse them and they can leak, vent, or burst. The longer lead is positive (+).</li>
<li><strong>Verify voltage.</strong> Confirm your power supply outputs 9 V DC before connecting it to the circuit.</li>
<li><strong>Watch for shorts.</strong> Before powering up, visually inspect that no jumper wires bridge adjacent pins unintentionally.</li>
<li><strong>Use a current-limited supply if possible</strong> — or at least a 9 V battery (self-limiting) during initial testing.</li>
</ul>
<h3>Tools You'll Need</h3>
<div class="card">
<table style="width:100%;border-collapse:collapse;font-size:.9rem">
<thead><tr><th style="text-align:left;padding:.4rem .75rem;color:var(--accent);background:#21262d;border-bottom:2px solid var(--border)">Tool</th><th style="text-align:left;padding:.4rem .75rem;color:var(--accent);background:#21262d;border-bottom:2px solid var(--border)">Purpose</th></tr></thead>
<tbody>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">Breadboard (full-size, 830 points)</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Platform for building the circuit without soldering</td></tr>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">Jumper wires (assorted colors)</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Connecting components on the breadboard</td></tr>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">Multimeter</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Verify voltages, check continuity, measure resistance</td></tr>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">Wire cutters / strippers</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Trim and strip jumper wires to length</td></tr>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">Audio source (phone, MP3 player, PC)</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Provides the stereo audio input signal</td></tr>
<tr><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border)">3.5 mm stereo audio cable</td><td style="padding:.4rem .75rem;border-bottom:1px solid var(--border);color:var(--muted)">Carries left/right signals from source to amplifier</td></tr>
<tr><td style="padding:.4rem .75rem">9 V battery with snap connector OR 9 V DC power supply</td><td style="padding:.4rem .75rem;color:var(--muted)">Power for the circuit</td></tr>
</tbody>
</table>
</div>
<h3>Basic Knowledge Assumed</h3>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:1rem">
<li>How to read a schematic diagram (symbols for resistors, capacitors, ICs).</li>
<li>Understanding of positive/negative terminals and ground.</li>
<li>Familiarity with breadboard internal wiring (rows are connected; power rails run the length).</li>
</ul>
<div class="callout info">
<strong>📖 Breadboard basics:</strong> A standard breadboard has two sets of horizontal power rails on each side (usually marked red + and blue −). The central area is divided into rows of five connected holes. Components inserted in the same row share an electrical connection.
</div>
</section>
<!-- ═══════════════ SECTION 3: PARTS LIST ═══════════════ -->
<section id="parts">
<h2>Complete Parts List (Bill of Materials)</h2>
<p>The following table lists every component you need. Quantities are for a complete stereo amplifier with both left and right channels.</p>
<div style="overflow-x:auto;border-radius:8px;border:1px solid var(--border)">
<table class="bom">
<thead>
<tr><th>#</th><th>Component / Part Number</th><th class="qty">Qty</th><th>Purpose / Role in Circuit</th></tr>
</thead>
<tbody>
<tr><td>1</td><td><strong>LM386N-1</strong> — Low Voltage Audio Power Amplifier IC (DIP-8)</td><td class="qty">2</td><td>One per channel. The core amplifier chip.</td></tr>
<tr><td>2</td><td><strong>10 µF / 25 V electrolytic capacitor</strong></td><td class="qty">4</td><td>Two for gain-setting (pins 1–8 on each LM386). Two as input coupling capacitors.</td></tr>
<tr><td>3</td><td><strong>220 µF / 25 V electrolytic capacitor</strong></td><td class="qty">2</td><td>Output coupling — blocks DC from reaching the speakers. One per channel.</td></tr>
<tr><td>4</td><td><strong>10 µF / 25 V electrolytic capacitor (bypass)</strong></td><td class="qty">2</td><td>Bypass capacitors on pin 6 of each LM386 to improve transient response.</td></tr>
<tr><td>5</td><td><strong>100 nF (0.1 µF) ceramic capacitor</strong></td><td class="qty">2</td><td>Power supply decoupling — one per channel, placed close to each IC's V<sub>CC</sub> pin.</td></tr>
<tr><td>6</td><td><strong>10 kΩ dual-gang potentiometer (linear taper)</strong></td><td class="qty">1</td><td>Stereo volume control — adjusts input signal level to both channels simultaneously.</td></tr>
<tr><td>7</td><td><strong>3.5 mm stereo audio jack (TRS, PCB-mount or panel-mount)</strong></td><td class="qty">1</td><td>Audio input connector for your music source.</td></tr>
<tr><td>8</td><td><strong>8 Ω / 3 W speaker</strong></td><td class="qty">2</td><td>Left and right stereo speakers. Small full-range drivers work well.</td></tr>
<tr><td>9</td><td><strong>Speaker binding posts or terminal blocks</strong></td><td class="qty">4</td><td>Screw terminals for connecting speaker wires to the breadboard (optional but recommended).</td></tr>
<tr><td>10</td><td><strong>9 V battery with snap connector</strong> OR 9 V DC wall adapter</td><td class="qty">1</td><td>Power supply. The LM386 operates from 4–15 V; 9 V is ideal.</td></tr>
<tr><td>11</td><td><strong>Jumper wires (male-to-male, assorted colors)</strong></td><td class="qty">~30</td><td>Breadboard interconnections. Use red for +V, black for GND, other colors for signals.</td></tr>
<tr><td>12</td><td><strong>Full-size breadboard (830 tie-points)</strong></td><td class="qty">1</td><td>The platform on which the entire circuit is assembled.</td></tr>
<tr><td>13</td><td><strong>IC socket (DIP-8, optional but recommended)</strong></td><td class="qty">2</td><td>Allows you to remove the LM386 without damaging it if something goes wrong.</td></tr>
</tbody>
</table>
</div>
<h3>LM386 Pinout Reference</h3>
<p>The LM386 comes in an 8-pin DIP package. Notch on the top indicates pin 1 (left side, notch facing you):</p>
<table class="pin-table">
<thead><tr><th>Pin</th><th>Name</th><th>Description</th></tr></thead>
<tbody>
<tr><td style="color:var(--accent);font-weight:700">1</td><td>G<sub>N</sub> (Gain −)</td><td>External gain terminal — connect to pin 8 via capacitor for 200× gain.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">2</td><td>V<sub>in−</sub> (Inverting Input)</td><td>Inverting audio input. Usually grounded in single-supply config.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">3</td><td>V<sub>in+</sub> (Non-Inverting Input)</td><td>Non-inverting audio input — signal enters here via coupling capacitor.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">4</td><td>GND</td><td>Circuit ground. Connect to the negative rail.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">5</td><td>V<sub>out</sub> (Output)</td><td>Amplified audio output — connects to speaker via coupling capacitor.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">6</td><td>C<sub>bypass</sub></td><td>Bypass capacitor terminal. Connect 20 µF cap here to ground for better performance.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">7</td><td>V<sub>CC</sub> (Supply)</td><td>Positive supply voltage (6–15 V). Connect to +9 V rail.</td></tr>
<tr><td style="color:var(--accent);font-weight:700">8</td><td>G<sub>P</sub> (Gain +)</td><td>External gain terminal — paired with pin 1 for gain setting.</td></tr>
</tbody>
</table>
</section>
<!-- ═══════════════ SECTION 4: SCHEMATIC DIAGRAM ═══════════════ -->
<section id="schematic">
<h2>Schematic Diagram</h2>
<p>The schematic below shows the complete stereo amplifier circuit. The left channel (top) and right channel (bottom) are mirror images, each centered around one LM386 IC.</p>
<div class="diagram-wrap">
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 900 720" width="900" height="720" font-family="'Courier New',monospace" font-size="11">
<!-- Background -->
<rect width="900" height="720" fill="#0f1923" rx="8"/>
<!-- Title block -->
<text x="450" y="22" text-anchor="middle" fill="#e6edf3" font-size="14" font-weight="bold">Stereo Audio Amplifier — Schematic (LM386 × 2)</text>
<!-- ═══ LEFT CHANNEL (top half) ═══ -->
<text x="50" y="55" fill="#58a6ff" font-size="13" font-weight="bold">LEFT CHANNEL</text>
<!-- Audio input label -->
<text x="40" y="95" fill="#d29922" font-size="10">Audio In L</text>
<!-- Input wire from left edge to C_in -->
<line x1="30" y1="100" x2="80" y2="100" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Coupling capacitor C_in_L (10uF) - vertical symbol -->
<rect x="74" y="85" width="12" height="3" fill="#e6edf3"/>
<rect x="74" y="92" width="12" height="3" fill="#e6edf3"/>
<line x1="80" y1="85" x2="80" y2="100" stroke="#e6edf3" stroke-width="1.5"/>
<text x="95" y="97" fill="#bc8cff" font-size="9">C_in_L</text>
<text x="95" y="108" fill="#8b949e" font-size="8">10µF</text>
<!-- Wire from C_out to pot -->
<line x1="86" y1="100" x2="130" y2="100" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Potentiometer symbol (volume control) -->
<rect x="130" y="78" width="40" height="22" fill="none" stroke="#d29922" stroke-width="1.5" rx="2"/>
<line x1="150" y1="78" x2="150" y2="68" stroke="#d29922" stroke-width="1.5"/>
<polygon points="146,72 154,72 150,66" fill="#d29922"/>
<text x="132" y="74" fill="#bc8cff" font-size="8">VOL</text>
<text x="132" y="115" fill="#8b949e" font-size="8">10kΩ dual-gang</text>
<!-- Wire from pot wiper to LM386 pin 3 -->
<line x1="170" y1="100" x2="250" y2="100" stroke="#e6edf3" stroke-width="1.5"/>
<!-- LM386 IC box (left channel) -->
<rect x="250" y="40" width="90" height="170" fill="#1c2333" stroke="#58a6ff" stroke-width="2" rx="4"/>
<text x="295" y="62" text-anchor="middle" fill="#58a6ff" font-size="12" font-weight="bold">LM386</text>
<text x="295" y="75" text-anchor="middle" fill="#8b949e" font-size="8">(Left)</text>
<!-- Pin labels on left side (pins 1-4) -->
<line x1="250" y1="65" x2="235" y2="65" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="69" text-anchor="end" fill="#e6edf3" font-size="9">Pin 1</text>
<line x1="250" y1="90" x2="235" y2="90" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="94" text-anchor="end" fill="#e6edf3" font-size="9">Pin 2</text>
<line x1="250" y1="115" x2="235" y2="115" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="119" text-anchor="end" fill="#e6edf3" font-size="9">Pin 3</text>
<line x1="250" y1="140" x2="235" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="144" text-anchor="end" fill="#e6edf3" font-size="9">Pin 4</text>
<!-- Pin labels on right side (pins 5-8) -->
<line x1="340" y1="65" x2="355" y2="65" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="69" fill="#e6edf3" font-size="9">Pin 8</text>
<line x1="340" y1="90" x2="355" y2="90" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="94" fill="#e6edf3" font-size="9">Pin 7</text>
<line x1="340" y1="115" x2="355" y2="115" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="119" fill="#e6edf3" font-size="9">Pin 6</text>
<line x1="340" y1="140" x2="355" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="144" fill="#e6edf3" font-size="9">Pin 5</text>
<!-- Pin function labels -->
<text x="228" y="57" text-anchor="end" fill="#bc8cff" font-size="7">G_N</text>
<text x="228" y="103" text-anchor="end" fill="#bc8cff" font-size="7">V_in−</text>
<text x="228" y="128" text-anchor="end" fill="#bc8cff" font-size="7">V_in+</text>
<text x="228" y="153" text-anchor="end" fill="#bc8cff" font-size="7">GND</text>
<text x="358" y="57" fill="#bc8cff" font-size="7">G_P</text>
<text x="358" y="103" fill="#bc8cff" font-size="7">V_CC</text>
<text x="358" y="128" fill="#bc8cff" font-size="7">C_byp</text>
<text x="358" y="153" fill="#bc8cff" font-size="7">V_out</text>
<!-- Gain capacitor between pin 1 and pin 8 -->
<line x1="235" y1="65" x2="200" y2="65" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="65" x2="200" y2="48" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="194" y="42" width="12" height="3" fill="#bc8cff"/>
<rect x="194" y="49" width="12" height="3" fill="#bc8cff"/>
<line x1="200" y1="52" x2="200" y2="36" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="36" x2="355" y2="36" stroke="#e6edf3" stroke-width="1.5"/>
<text x="180" y="47" text-anchor="end" fill="#bc8cff" font-size="9">C_gain_L</text>
<text x="180" y="58" text-anchor="end" fill="#8b949e" font-size="8">10µF</text>
<!-- Pin 2 (inverting input) to ground -->
<line x1="235" y1="90" x2="200" y2="90" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="90" x2="200" y2="170" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Pin 4 (GND) to ground rail -->
<line x1="235" y1="140" x2="200" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="140" x2="200" y2="170" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Ground symbol (left channel) -->
<line x1="185" y1="170" x2="215" y2="170" stroke="#3fb950" stroke-width="2"/>
<line x1="190" y1="176" x2="210" y2="176" stroke="#3fb950" stroke-width="1.5"/>
<line x1="194" y1="182" x2="206" y2="182" stroke="#3fb950" stroke-width="1"/>
<!-- VCC connection (pin 7) -->
<line x1="355" y1="90" x2="400" y2="90" stroke="#e6edf3" stroke-width="1.5"/>
<text x="405" y="87" fill="#f85149" font-size="9">+VCC</text>
<!-- Decoupling cap on VCC -->
<line x1="400" y1="90" x2="430" y2="90" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="424" y="78" width="12" height="3" fill="#bc8cff"/>
<rect x="424" y="85" width="12" height="3" fill="#bc8cff"/>
<line x1="430" y1="88" x2="430" y2="70" stroke="#e6edf3" stroke-width="1.5"/>
<text x="435" y="82" fill="#bc8cff" font-size="8">C_dec_L</text>
<text x="435" y="93" fill="#8b949e" font-size="7">100nF</text>
<!-- Bypass cap on pin 6 -->
<line x1="355" y1="115" x2="380" y2="115" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="374" y="103" width="12" height="3" fill="#bc8cff"/>
<rect x="374" y="110" width="12" height="3" fill="#bc8cff"/>
<line x1="380" y1="113" x2="380" y2="135" stroke="#e6edf3" stroke-width="1.5"/>
<text x="385" y="109" fill="#bc8cff" font-size="8">C_byp_L</text>
<text x="385" y="120" fill="#8b949e" font-size="7">10µF</text>
<!-- Output from pin 5 -->
<line x1="355" y1="140" x2="420" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Output coupling capacitor -->
<rect x="414" y="128" width="12" height="3" fill="#bc8cff"/>
<rect x="414" y="135" width="12" height="3" fill="#bc8cff"/>
<line x1="420" y1="131" x2="420" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<text x="425" y="127" fill="#bc8cff" font-size="9">C_out_L</text>
<text x="425" y="138" fill="#8b949e" font-size="8">220µF</text>
<!-- Wire to speaker -->
<line x1="426" y1="140" x2="500" y2="140" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Speaker symbol (left) -->
<path d="M 500,120 L 500,160" stroke="#39d2c0" stroke-width="2" fill="none"/>
<path d="M 500,120 Q 520,140 500,160" stroke="#39d2c0" stroke-width="2" fill="none"/>
<rect x="500" y="118" width="2" height="44" fill="#39d2c0"/>
<text x="510" y="137" fill="#bc8cff" font-size="9">Speaker L</text>
<text x="510" y="148" fill="#8b949e" font-size="8">8Ω / 3W</text>
<!-- Speaker ground -->
<line x1="500" y1="160" x2="500" y2="170" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="485" y1="170" x2="515" y2="170" stroke="#3fb950" stroke-width="2"/>
<!-- ═══ RIGHT CHANNEL (bottom half) — mirror image ═══ -->
<text x="50" y="345" fill="#f85149" font-size="13" font-weight="bold">RIGHT CHANNEL</text>
<text x="40" y="385" fill="#d29922" font-size="10">Audio In R</text>
<line x1="30" y1="390" x2="80" y2="390" stroke="#e6edf3" stroke-width="1.5"/>
<!-- C_in_R -->
<rect x="74" y="375" width="12" height="3" fill="#e6edf3"/>
<rect x="74" y="382" width="12" height="3" fill="#e6edf3"/>
<line x1="80" y1="375" x2="80" y2="390" stroke="#e6edf3" stroke-width="1.5"/>
<text x="95" y="387" fill="#bc8cff" font-size="9">C_in_R</text>
<text x="95" y="398" fill="#8b949e" font-size="8">10µF</text>
<!-- Wire to pot -->
<line x1="86" y1="390" x2="130" y2="390" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Pot (right channel share same dual-gang) -->
<rect x="130" y="368" width="40" height="22" fill="none" stroke="#d29922" stroke-width="1.5" rx="2"/>
<line x1="150" y1="368" x2="150" y2="358" stroke="#d29922" stroke-width="1.5"/>
<polygon points="146,362 154,362 150,356" fill="#d29922"/>
<!-- Wire from pot to LM386 pin 3 -->
<line x1="170" y1="390" x2="250" y2="390" stroke="#e6edf3" stroke-width="1.5"/>
<!-- LM386 IC box (right channel) -->
<rect x="250" y="330" width="90" height="170" fill="#1c2333" stroke="#f85149" stroke-width="2" rx="4"/>
<text x="295" y="352" text-anchor="middle" fill="#f85149" font-size="12" font-weight="bold">LM386</text>
<text x="295" y="365" text-anchor="middle" fill="#8b949e" font-size="8">(Right)</text>
<!-- Pins left side -->
<line x1="250" y1="355" x2="235" y2="355" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="359" text-anchor="end" fill="#e6edf3" font-size="9">Pin 1</text>
<line x1="250" y1="380" x2="235" y2="380" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="384" text-anchor="end" fill="#e6edf3" font-size="9">Pin 2</text>
<line x1="250" y1="405" x2="235" y2="405" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="409" text-anchor="end" fill="#e6edf3" font-size="9">Pin 3</text>
<line x1="250" y1="430" x2="235" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<text x="228" y="434" text-anchor="end" fill="#e6edf3" font-size="9">Pin 4</text>
<!-- Pins right side -->
<line x1="340" y1="355" x2="355" y2="355" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="359" fill="#e6edf3" font-size="9">Pin 8</text>
<line x1="340" y1="380" x2="355" y2="380" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="384" fill="#e6edf3" font-size="9">Pin 7</text>
<line x1="340" y1="405" x2="355" y2="405" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="409" fill="#e6edf3" font-size="9">Pin 6</text>
<line x1="340" y1="430" x2="355" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<text x="358" y="434" fill="#e6edf3" font-size="9">Pin 5</text>
<!-- Gain cap right -->
<line x1="235" y1="355" x2="200" y2="355" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="355" x2="200" y2="338" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="194" y="332" width="12" height="3" fill="#bc8cff"/>
<rect x="194" y="339" width="12" height="3" fill="#bc8cff"/>
<line x1="200" y1="342" x2="200" y2="326" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="326" x2="355" y2="326" stroke="#e6edf3" stroke-width="1.5"/>
<text x="180" y="337" text-anchor="end" fill="#bc8cff" font-size="9">C_gain_R</text>
<text x="180" y="348" text-anchor="end" fill="#8b949e" font-size="8">10µF</text>
<!-- Pin 2 to ground -->
<line x1="235" y1="380" x2="200" y2="380" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="380" x2="200" y2="460" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Pin 4 to ground -->
<line x1="235" y1="430" x2="200" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="200" y1="430" x2="200" y2="460" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Ground symbol (right) -->
<line x1="185" y1="460" x2="215" y2="460" stroke="#3fb950" stroke-width="2"/>
<line x1="190" y1="466" x2="210" y2="466" stroke="#3fb950" stroke-width="1.5"/>
<line x1="194" y1="472" x2="206" y2="472" stroke="#3fb950" stroke-width="1"/>
<!-- VCC right -->
<line x1="355" y1="380" x2="400" y2="380" stroke="#e6edf3" stroke-width="1.5"/>
<text x="405" y="377" fill="#f85149" font-size="9">+VCC</text>
<!-- Decoupling cap right -->
<line x1="400" y1="380" x2="430" y2="380" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="424" y="368" width="12" height="3" fill="#bc8cff"/>
<rect x="424" y="375" width="12" height="3" fill="#bc8cff"/>
<line x1="430" y1="378" x2="430" y2="360" stroke="#e6edf3" stroke-width="1.5"/>
<text x="435" y="372" fill="#bc8cff" font-size="8">C_dec_R</text>
<text x="435" y="383" fill="#8b949e" font-size="7">100nF</text>
<!-- Bypass cap right -->
<line x1="355" y1="405" x2="380" y2="405" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="374" y="393" width="12" height="3" fill="#bc8cff"/>
<rect x="374" y="400" width="12" height="3" fill="#bc8cff"/>
<line x1="380" y1="403" x2="380" y2="425" stroke="#e6edf3" stroke-width="1.5"/>
<text x="385" y="399" fill="#bc8cff" font-size="8">C_byp_R</text>
<text x="385" y="410" fill="#8b949e" font-size="7">10µF</text>
<!-- Output right -->
<line x1="355" y1="430" x2="420" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<rect x="414" y="418" width="12" height="3" fill="#bc8cff"/>
<rect x="414" y="425" width="12" height="3" fill="#bc8cff"/>
<line x1="420" y1="421" x2="420" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<text x="425" y="417" fill="#bc8cff" font-size="9">C_out_R</text>
<text x="425" y="428" fill="#8b949e" font-size="8">220µF</text>
<!-- Wire to speaker right -->
<line x1="426" y1="430" x2="500" y2="430" stroke="#e6edf3" stroke-width="1.5"/>
<!-- Speaker symbol (right) -->
<path d="M 500,410 L 500,450" stroke="#39d2c0" stroke-width="2" fill="none"/>
<path d="M 500,410 Q 520,430 500,450" stroke="#39d2c0" stroke-width="2" fill="none"/>
<rect x="500" y="408" width="2" height="44" fill="#39d2c0"/>
<text x="510" y="427" fill="#bc8cff" font-size="9">Speaker R</text>
<text x="510" y="438" fill="#8b949e" font-size="8">8Ω / 3W</text>
<!-- Speaker ground right -->
<line x1="500" y1="450" x2="500" y2="460" stroke="#e6edf3" stroke-width="1.5"/>
<line x1="485" y1="460" x2="515" y2="460" stroke="#3fb950" stroke-width="2"/>
<!-- ═══ POWER SUPPLY (right side) ═══ -->
<text x="700" y="80" fill="#f85149" font-size="13" font-weight="bold">POWER SUPPLY</text>
<!-- Battery symbol -->
<rect x="680" y="100" width="80" height="120" fill="#1c2333" stroke="#f85149" stroke-width="1.5" rx="4"/>
<text x="720" y="125" text-anchor="middle" fill="#f85149" font-size="12" font-weight="bold">9V</text>
<text x="720" y="140" text-anchor="middle" fill="#e6edf3" font-size="10">Battery or</text>
<text x="720" y="155" text-anchor="middle" fill="#e6edf3" font-size="10">DC Supply</text>
<!-- +VCC line from battery -->
<line x1="720" y1="100" x2="720" y2="60" stroke="#f85149" stroke-width="2"/>
<circle cx="720" cy="60" r="3" fill="#f85149"/>
<text x="720" y="55" text-anchor="middle" fill="#f85149" font-size="9">+VCC</text>
<!-- VCC distribution lines -->
<line x1="720" y1="60" x2="430" y2="60" stroke="#f85149" stroke-width="1.5"/>
<line x1="430" y1="60" x2="430" y2="70" stroke="#f85149" stroke-width="1.5"/>
<!-- GND line from battery -->
<line x1="720" y1="220" x2="720" y2="260" stroke="#3fb950" stroke-width="2"/>
<circle cx="720" cy="260" r="3" fill="#3fb950"/>
<text x="720" y="278" text-anchor="middle" fill="#3fb950" font-size="9">GND</text>
<!-- GND distribution -->
<line x1="720" y1="260" x2="430" y2="260" stroke="#3fb950" stroke-width="1.5"/>
<line x1="430" y1="260" x2="430" y2="270" stroke="#3fb950" stroke-width="1.5"/>
<!-- ═══ AUDIO INPUT JACK (far left) ═══ -->
<text x="80" y="560" fill="#d29922" font-size="13" font-weight="bold">AUDIO INPUT</text>
<!-- 3.5mm jack symbol -->
<rect x="40" y="575" width="60" height="80" fill="#1c2333" stroke="#d29922" stroke-width="1.5" rx="4"/>
<circle cx="70" cy="595" r="6" fill="none" stroke="#d29922" stroke-width="1.5"/>
<line x1="70" y1="589" x2="70" y2="601" stroke="#d29922" stroke-width="1"/>
<text x="70" y="630" text-anchor="middle" fill="#e6edf3" font-size="9">3.5mm TRS</text>
<!-- Tip (Left) connection -->
<line x1="40" y1="585" x2="10" y2="585" stroke="#58a6ff" stroke-width="1.5"/>
<text x="8" y="582" text-anchor="end" fill="#58a6ff" font-size="8">Tip (L)</text>
<!-- Ring (Right) connection -->
<line x1="40" y1="610" x2="10" y2="610" stroke="#f85149" stroke-width="1.5"/>
<text x="8" y="607" text-anchor="end" fill="#f85149" font-size="8">Ring (R)</text>
<!-- Sleeve (GND) connection -->
<line x1="40" y1="635" x2="10" y2="635" stroke="#3fb950" stroke-width="1.5"/>
<text x="8" y="632" text-anchor="end" fill="#3fb950" font-size="8">Sleeve</text>
<!-- Connect tip to left channel input -->
<line x1="10" y1="585" x2="10" y2="100" stroke="#58a6ff" stroke-width="1"/>
<line x1="10" y1="100" x2="30" y2="100" stroke="#58a6ff" stroke-width="1"/>
<!-- Connect ring to right channel input -->
<line x1="10" y1="610" x2="10" y2="390" stroke="#f85149" stroke-width="1"/>
<line x1="10" y1="390" x2="30" y2="390" stroke="#f85149" stroke-width="1"/>
<!-- Connect sleeve to ground -->
<line x1="10" y1="635" x2="10" y2="460" stroke="#3fb950" stroke-width="1"/>
<line x1="10" y1="460" x2="185" y2="460" stroke="#3fb950" stroke-width="1"/>
<!-- ═══ Legend ═══ -->
<rect x="640" y="520" width="240" height="185" fill="#1c2333" stroke="#30363d" stroke-width="1" rx="4"/>
<text x="760" y="540" text-anchor="middle" fill="#e6edf3" font-size="11" font-weight="bold">Legend</text>
<line x1="660" y1="558" x2="690" y2="558" stroke="#f85149" stroke-width="2"/>
<text x="700" y="562" fill="#e6edf3" font-size="9">+VCC (positive supply)</text>
<line x1="660" y1="578" x2="690" y2="578" stroke="#3fb950" stroke-width="2"/>
<text x="700" y="582" fill="#e6edf3" font-size="9">GND (ground)</text>
<line x1="660" y1="598" x2="690" y2="598" stroke="#58a6ff" stroke-width="2"/>
<text x="700" y="602" fill="#e6edf3" font-size="9">Left channel signal</text>
<line x1="660" y1="618" x2="690" y2="618" stroke="#f85149" stroke-width="2"/>
<text x="700" y="622" fill="#e6edf3" font-size="9">Right channel signal</text>
<rect x="660" y="632" width="12" height="3" fill="#bc8cff"/>
<rect x="660" y="639" width="12" height="3" fill="#bc8cff"/>
<text x="700" y="645" fill="#e6edf3" font-size="9">Capacitor</text>
<rect x="660" y="655" width="20" height="10" fill="none" stroke="#d29922" stroke-width="1.5"/>
<text x="700" y="664" fill="#e6edf3" font-size="9">Potentiometer</text>
<!-- Signal flow arrows -->
<polygon points="80,100 85,97 85,103" fill="#58a6ff"/>
<polygon points="240,100 245,97 245,103" fill="#58a6ff"/>
<polygon points="410,140 415,137 415,143" fill="#e6edf3"/>
<polygon points="80,390 85,387 85,393" fill="#f85149"/>
<polygon points="240,390 245,387 245,393" fill="#f85149"/>
<polygon points="410,430 415,427 415,433" fill="#e6edf3"/>
</svg>
</div>
<div class="callout info">
<strong>📐 Reading the schematic:</strong> Signal flows from left to right. Audio enters through the 3.5 mm jack (Tip = Left, Ring = Right). Each channel passes through a coupling capacitor → volume potentiometer → LM386 amplifier → output coupling capacitor → speaker. The two channels share a common ground and power supply.
</div>
</section>
<!-- ═══════════════ SECTION 5: BREADBOARD LAYOUT ═══════════════ -->
<section id="breadboard">
<h2>Breadboard Wiring Layout</h2>
<p>The diagram below maps every component to its position on a standard full-size breadboard. The left channel occupies the top half; the right channel mirrors it below.</p>
<div class="diagram-wrap">
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 860 540" width="860" height="540" font-family="'Courier New',monospace" font-size="9">
<!-- Background -->
<rect width="860" height="540" fill="#0f1923" rx="8"/>
<text x="430" y="18" text-anchor="middle" fill="#e6edf3" font-size="13" font-weight="bold">Breadboard Wiring Layout — Top View</text>
<!-- Breadboard body -->
<rect x="50" y="30" width="760" height="480" fill="#1a2332" stroke="#30363d" stroke-width="2" rx="6"/>
<!-- Power rails (top) - red + -->
<rect x="55" y="35" width="750" height="14" fill="rgba(248,81,73,.1)" stroke="#f85149" stroke-width="1"/>
<text x="60" y="46" fill="#f85149" font-size="8">+VCC Rail</text>
<!-- Power rails (top) - blue - -->
<rect x="55" y="53" width="750" height="14" fill="rgba(63,185,80,.1)" stroke="#3fb950" stroke-width="1"/>
<text x="60" y="64" fill="#3fb950" font-size="8">GND Rail</text>
<!-- Center gap -->
<rect x="50" y="200" width="760" height="8" fill="#0d1117"/>
<!-- Power rails (bottom) - red + -->
<rect x="55" y="491" width="750" height="14" fill="rgba(248,81,73,.1)" stroke="#f85149" stroke-width="1"/>
<text x="60" y="502" fill="#f85149" font-size="8">+VCC Rail</text>
<!-- Power rails (bottom) - blue - -->
<rect x="55" y="473" width="750" height="14" fill="rgba(63,185,80,.1)" stroke="#3fb950" stroke-width="1"/>
<text x="60" y="484" fill="#3fb950" font-size="8">GND Rail</text>
<!-- Row indicators -->
<g fill="#8b949e" font-size="7">
<text x="52" y="80" text-anchor="end">A</text>
<text x="52" y="100" text-anchor="end">B</text>
<text x="52" y="120" text-anchor="end">C</text>
<text x="52" y="140" text-anchor="end">D</text>
<text x="52" y="160" text-anchor="end">E</text>
<text x="52" y="210" text-anchor="end">A'</text>
<text x="52" y="230" text-anchor="end">B'</text>
<text x="52" y="250" text-anchor="end">C'</text>
<text x="52" y="270" text-anchor="end">D'</text>
<text x="52" y="290" text-anchor="end">E'</text>
</g>
<!-- ═══ LEFT CHANNEL IC (LM386 #1) ═══ -->
<!-- IC footprint - straddles center gap, pins in rows D/E top and A'/B' bottom -->
<rect x="200" y="175" width="80" height="40" fill="#1c2333" stroke="#58a6ff" stroke-width="1.5" rx="3"/>
<text x="240" y="198" text-anchor="middle" fill="#58a6ff" font-size="9" font-weight="bold">LM386-L</text>
<!-- Pin dots on IC -->
<!-- Top side pins (left to right: 1,2,3,4) -->
<circle cx="210" cy="175" r="3" fill="#e6edf3"/>
<circle cx="225" cy="175" r="3" fill="#e6edf3"/>
<circle cx="240" cy="175" r="3" fill="#e6edf3"/>
<circle cx="255" cy="175" r="3" fill="#e6edf3"/>
<!-- Bottom side pins (right to left: 8,7,6,5) -->
<circle cx="270" cy="215" r="3" fill="#e6edf3"/>
<circle cx="255" cy="215" r="3" fill="#e6edf3"/>
<circle cx="240" cy="215" r="3" fill="#e6edf3"/>
<circle cx="225" cy="215" r="3" fill="#e6edf3"/>
<!-- Pin numbers -->
<text x="210" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">1</text>
<text x="225" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">2</text>
<text x="240" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">3</text>
<text x="255" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">4</text>
<text x="270" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">8</text>
<text x="255" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">7</text>
<text x="240" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">6</text>
<text x="225" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">5</text>
<!-- ═══ RIGHT CHANNEL IC (LM386 #2) ═══ -->
<rect x="480" y="175" width="80" height="40" fill="#1c2333" stroke="#f85149" stroke-width="1.5" rx="3"/>
<text x="520" y="198" text-anchor="middle" fill="#f85149" font-size="9" font-weight="bold">LM386-R</text>
<!-- Pin dots -->
<circle cx="490" cy="175" r="3" fill="#e6edf3"/>
<circle cx="505" cy="175" r="3" fill="#e6edf3"/>
<circle cx="520" cy="175" r="3" fill="#e6edf3"/>
<circle cx="535" cy="175" r="3" fill="#e6edf3"/>
<circle cx="550" cy="215" r="3" fill="#e6edf3"/>
<circle cx="535" cy="215" r="3" fill="#e6edf3"/>
<circle cx="520" cy="215" r="3" fill="#e6edf3"/>
<circle cx="505" cy="215" r="3" fill="#e6edf3"/>
<!-- Pin numbers -->
<text x="490" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">1</text>
<text x="505" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">2</text>
<text x="520" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">3</text>
<text x="535" y="170" text-anchor="middle" fill="#bc8cff" font-size="7">4</text>
<text x="550" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">8</text>
<text x="535" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">7</text>
<text x="520" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">6</text>
<text x="505" y="230" text-anchor="middle" fill="#bc8cff" font-size="7">5</text>
<!-- ═══ LEFT CHANNEL COMPONENTS ═══ -->
<!-- C_in_L (10uF) - near pin 3 -->
<rect x="240" y="130" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="258" y="139" fill="#e6edf3" font-size="7">C_in_L</text>
<!-- Wire from C_in to pin 3 -->
<line x1="248" y1="138" x2="240" y2="175" stroke="#58a6ff" stroke-width="1"/>
<!-- Audio input jack (left) -->
<rect x="100" y="125" width="40" height="20" fill="#1c2333" stroke="#d29922" stroke-width="1" rx="2"/>
<text x="120" y="139" text-anchor="middle" fill="#e6edf3" font-size="7">JACK-L</text>
<!-- Wire from jack to C_in -->
<line x1="140" y1="135" x2="240" y2="135" stroke="#58a6ff" stroke-width="1"/>
<!-- Potentiometer (left channel) -->
<rect x="170" y="90" width="30" height="16" fill="none" stroke="#d29922" stroke-width="1.5" rx="2"/>
<text x="185" y="88" text-anchor="middle" fill="#e6edf3" font-size="7">POT-L</text>
<!-- Wire from C_in to pot -->
<line x1="240" y1="130" x2="240" y2="98" stroke="#58a6ff" stroke-width="1"/>
<line x1="240" y1="98" x2="200" y2="98" stroke="#58a6ff" stroke-width="1"/>
<!-- Wire from pot wiper to pin 3 -->
<line x1="185" y1="90" x2="185" y2="75" stroke="#d29922" stroke-width="1"/>
<line x1="185" y1="75" x2="240" y2="75" stroke="#d29922" stroke-width="1"/>
<!-- C_gain_L (pin 1 to pin 8) -->
<rect x="160" y="130" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="145" y="139" text-anchor="end" fill="#e6edf3" font-size="7">C_gain_L</text>
<!-- Wire pin 1 to C_gain -->
<line x1="210" y1="175" x2="210" y2="148" stroke="#bc8cff" stroke-width="1"/>
<line x1="210" y1="148" x2="176" y2="148" stroke="#bc8cff" stroke-width="1"/>
<!-- Wire C_gain to pin 8 -->
<line x1="168" y1="134" x2="168" y2="105" stroke="#bc8cff" stroke-width="1"/>
<line x1="168" y1="105" x2="270" y2="105" stroke="#bc8cff" stroke-width="1"/>
<!-- Pin 2 to GND -->
<line x1="225" y1="175" x2="225" y2="67" stroke="#3fb950" stroke-width="1"/>
<!-- Pin 4 to GND rail -->
<line x1="255" y1="175" x2="255" y2="67" stroke="#3fb950" stroke-width="1"/>
<!-- VCC to pin 7 -->
<line x1="255" y1="215" x2="255" y2="49" stroke="#f85149" stroke-width="1"/>
<!-- C_dec_L on VCC -->
<rect x="260" y="38" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="278" y="46" fill="#e6edf3" font-size="7">C_dec_L</text>
<!-- C_byp_L on pin 6 -->
<rect x="240" y="250" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="258" y="259" fill="#e6edf3" font-size="7">C_byp_L</text>
<!-- Wire pin 6 to C_byp -->
<line x1="240" y1="215" x2="240" y2="250" stroke="#bc8cff" stroke-width="1"/>
<!-- C_byp to GND rail (bottom) -->
<line x1="248" y1="258" x2="248" y2="473" stroke="#3fb950" stroke-width="1"/>
<!-- Output pin 5 to C_out_L -->
<rect x="225" y="260" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="243" y="269" fill="#e6edf3" font-size="7">C_out_L</text>
<!-- Wire pin 5 to C_out -->
<line x1="225" y1="215" x2="225" y2="260" stroke="#bc8cff" stroke-width="1"/>
<!-- Speaker L connection -->
<rect x="140" y="310" width="50" height="20" fill="#1c2333" stroke="#39d2c0" stroke-width="1.5" rx="2"/>
<text x="165" y="324" text-anchor="middle" fill="#39d2c0" font-size="8">SPKR-L</text>
<!-- Wire from C_out to speaker -->
<line x1="225" y1="268" x2="225" y2="320" stroke="#e6edf3" stroke-width="1"/>
<line x1="225" y1="320" x2="190" y2="320" stroke="#e6edf3" stroke-width="1"/>
<!-- Speaker ground -->
<line x1="140" y1="320" x2="120" y2="320" stroke="#3fb950" stroke-width="1"/>
<line x1="120" y1="320" x2="120" y2="473" stroke="#3fb950" stroke-width="1"/>
<!-- ═══ RIGHT CHANNEL COMPONENTS (mirrored) ═══ -->
<!-- C_in_R -->
<rect x="520" y="130" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="538" y="139" fill="#e6edf3" font-size="7">C_in_R</text>
<!-- Wire from C_in to pin 3 -->
<line x1="520" y1="138" x2="520" y2="175" stroke="#f85149" stroke-width="1"/>
<!-- Audio input jack (right) -->
<rect x="620" y="125" width="40" height="20" fill="#1c2333" stroke="#d29922" stroke-width="1" rx="2"/>
<text x="640" y="139" text-anchor="middle" fill="#e6edf3" font-size="7">JACK-R</text>
<!-- Wire from jack to C_in -->
<line x1="620" y1="135" x2="536" y2="135" stroke="#f85149" stroke-width="1"/>
<!-- Potentiometer (right channel) -->
<rect x="560" y="90" width="30" height="16" fill="none" stroke="#d29922" stroke-width="1.5" rx="2"/>
<text x="575" y="88" text-anchor="middle" fill="#e6edf3" font-size="7">POT-R</text>
<!-- Wire from C_in to pot -->
<line x1="520" y1="130" x2="520" y2="98" stroke="#f85149" stroke-width="1"/>
<line x1="520" y1="98" x2="590" y2="98" stroke="#f85149" stroke-width="1"/>
<!-- Wire from pot wiper to pin 3 -->
<line x1="575" y1="90" x2="575" y2="75" stroke="#d29922" stroke-width="1"/>
<line x1="575" y1="75" x2="520" y2="75" stroke="#d29922" stroke-width="1"/>
<!-- C_gain_R -->
<rect x="680" y="130" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="700" y="139" fill="#e6edf3" font-size="7">C_gain_R</text>
<!-- Wire pin 1 to C_gain -->
<line x1="490" y1="175" x2="490" y2="148" stroke="#bc8cff" stroke-width="1"/>
<line x1="490" y1="148" x2="680" y2="148" stroke="#bc8cff" stroke-width="1"/>
<!-- Wire C_gain to pin 8 -->
<line x1="688" y1="134" x2="688" y2="105" stroke="#bc8cff" stroke-width="1"/>
<line x1="688" y1="105" x2="550" y2="105" stroke="#bc8cff" stroke-width="1"/>
<!-- Pin 2 to GND -->
<line x1="505" y1="175" x2="505" y2="67" stroke="#3fb950" stroke-width="1"/>
<!-- Pin 4 to GND rail -->
<line x1="535" y1="175" x2="535" y2="67" stroke="#3fb950" stroke-width="1"/>
<!-- VCC to pin 7 -->
<line x1="535" y1="215" x2="535" y2="49" stroke="#f85149" stroke-width="1"/>
<!-- C_dec_R on VCC -->
<rect x="540" y="38" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="558" y="46" fill="#e6edf3" font-size="7">C_dec_R</text>
<!-- C_byp_R on pin 6 -->
<rect x="520" y="250" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="538" y="259" fill="#e6edf3" font-size="7">C_byp_R</text>
<!-- Wire pin 6 to C_byp -->
<line x1="520" y1="215" x2="520" y2="250" stroke="#bc8cff" stroke-width="1"/>
<!-- C_byp to GND rail (bottom) -->
<line x1="528" y1="258" x2="528" y2="473" stroke="#3fb950" stroke-width="1"/>
<!-- Output pin 5 to C_out_R -->
<rect x="505" y="260" width="16" height="8" fill="#bc8cff" rx="1"/>
<text x="523" y="269" fill="#e6edf3" font-size="7">C_out_R</text>
<!-- Wire pin 5 to C_out -->
<line x1="505" y1="215" x2="505" y2="260" stroke="#bc8cff" stroke-width="1"/>
<!-- Speaker R connection -->
<rect x="670" y="310" width="50" height="20" fill="#1c2333" stroke="#39d2c0" stroke-width="1.5" rx="2"/>
<text x="695" y="324" text-anchor="middle" fill="#39d2c0" font-size="8">SPKR-R</text>
<!-- Wire from C_out to speaker -->
<line x1="505" y1="268" x2="505" y2="320" stroke="#e6edf3" stroke-width="1"/>
<line x1="505" y1="320" x2="670" y2="320" stroke="#e6edf3" stroke-width="1"/>
<!-- Speaker ground -->
<line x1="720" y1="320" x2="740" y2="320" stroke="#3fb950" stroke-width="1"/>
<line x1="740" y1="320" x2="740" y2="473" stroke="#3fb950" stroke-width="1"/>
<!-- ═══ POWER SUPPLY CONNECTIONS ═══ -->
<!-- Battery snap to top VCC rail -->
<rect x="760" y="280" width="80" height="40" fill="#1c2333" stroke="#f85149" stroke-width="1.5" rx="3"/>
<text x="800" y="300" text-anchor="middle" fill="#f85149" font-size="9">9V</text>
<text x="800" y="312" text-anchor="middle" fill="#e6edf3" font-size="7">Battery</text>
<!-- + to VCC rail -->
<line x1="760" y1="295" x2="740" y2="295" stroke="#f85149" stroke-width="1.5"/>
<line x1="740" y1="295" x2="740" y2="42" stroke="#f85149" stroke-width="1.5"/>
<!-- - to GND rail -->
<line x1="760" y1="315" x2="740" y2="315" stroke="#3fb950" stroke-width="1.5"/>
<line x1="740" y1="315" x2="740" y2="60" stroke="#3fb950" stroke-width="1.5"/>
<!-- ═══ LEGEND ═══ -->
<rect x="680" y="380" width="165" height="140" fill="#1c2333" stroke="#30363d" stroke-width="1" rx="4"/>
<text x="762" y="398" text-anchor="middle" fill="#e6edf3" font-size="9" font-weight="bold">Legend</text>
<rect x="690" y="408" width="12" height="6" fill="#58a6ff" rx="1"/>
<text x="708" y="415" fill="#e6edf3" font-size="7">Left channel</text>
<rect x="690" y="422" width="12" height="6" fill="#f85149" rx="1"/>
<text x="708" y="429" fill="#e6edf3" font-size="7">Right channel</text>
<rect x="690" y="436" width="12" height="6" fill="#bc8cff" rx="1"/>
<text x="708" y="443" fill="#e6edf3" font-size="7">Capacitor</text>
<rect x="690" y="450" width="12" height="6" fill="none" stroke="#d29922" stroke-width="1"/>
<text x="708" y="457" fill="#e6edf3" font-size="7">Potentiometer</text>
<rect x="690" y="464" width="12" height="6" fill="#39d2c0" rx="1"/>
<text x="708" y="471" fill="#e6edf3" font-size="7">Speaker</text>
<line x1="690" y1="485" x2="702" y2="485" stroke="#f85149" stroke-width="2"/>
<text x="708" y="489" fill="#e6edf3" font-size="7">+VCC</text>
<line x1="690" y1="500" x2="702" y2="500" stroke="#3fb950" stroke-width="2"/>
<text x="708" y="504" fill="#e6edf3" font-size="7">GND</text>
</svg>
</div>
<div class="callout warn">
<strong>⚡ Important:</strong> The two LM386 ICs straddle the center gap of the breadboard. Each pin on one side of the gap connects to a different row — this is intentional and allows you to wire each pin independently. Make sure the notch (pin 1 indicator) faces left as shown.
</div>
</section>
<!-- ═══════════════ SECTION 6: ASSEMBLY STEPS ═══════════════ -->
<section id="assembly">
<h2>Step-by-Step Assembly Instructions</h2>
<p>Follow these steps in order. Work on one channel at a time — complete the left channel fully, then mirror it for the right channel.</p>
<div class="step">
<div class="step-num">1</div>
<div class="step-body">
<h4>Place the LM386 ICs on the Breadboard</h4>
<p>Insert each LM386 so it straddles the center gap. The notch (or dot) on the top of the chip marks pin 1 — orient it to the left side. Pin 1 should be in row D, and pin 8 in row A' (bottom section). Leave a few rows between the two ICs for wiring clearance.</p>
<div class="callout info" style="margin-top:.5rem">If you're using IC sockets, insert the sockets first, then plug the LM386 chips into them. This protects the IC if something goes wrong.</div>
</div>
</div>
<div class="step">
<div class="step-num">2</div>
<div class="step-body">
<h4>Set Up the Power Rails</h4>
<p>Connect the red (+) power rail on both sides of the breadboard together with a jumper wire. Do the same for the blue (−) / green ground rails. These will carry +9 V and GND to all components.</p>
</div>
</div>
<div class="step">
<div class="step-num">3</div>
<div class="step-body">
<h4>Connect Power Supply to Each IC</h4>
<p><strong>Pin 7 (V<sub>CC</sub>)</strong> on each LM386 → jumper wire to the +VCC rail.<br>
<strong>Pin 4 (GND)</strong> on each LM386 → jumper wire to the GND rail.</p>
</div>
</div>
<div class="step">
<div class="step-num">4</div>
<div class="step-body">
<h4>Add Decoupling Capacitors</h4>
<p>Place a <strong>100 nF ceramic capacitor</strong> between the +VCC rail and GND rail, as close to each IC's pin 7 as possible. This filters high-frequency noise from the power supply. The ceramic caps are non-polarized — orientation doesn't matter.</p>
</div>
</div>
<div class="step">
<div class="step-num">5</div>
<div class="step-body">
<h4>Set Gain to Maximum (200×)</h4>
<p>Connect a <strong>10 µF electrolytic capacitor</strong> between <strong>pin 1 and pin 8</strong> on each LM386. The longer lead (+) goes to pin 8; the shorter lead (−) goes to pin 1. This sets the internal gain resistor to maximum.</p>
<div class="callout warn" style="margin-top:.5rem">⚡ Electrolytic capacitors are polarized! Reverse them and they can be damaged. The longer lead is always positive (+).</div>
</div>
</div>
<div class="step">
<div class="step-num">6</div>
<div class="step-body">
<h4>Add Bypass Capacitors (Pin 6)</h4>
<p>Connect a <strong>10 µF electrolytic capacitor</strong> from <strong>pin 6 to GND</strong> on each LM386. Positive lead (+) to pin 6, negative lead (−) to ground. This improves transient response and reduces distortion.</p>
</div>
</div>
<div class="step">
<div class="step-num">7</div>
<div class="step-body">
<h4>Ground the Inverting Input (Pin 2)</h4>
<p>Connect a jumper wire from <strong>pin 2 to GND</strong> on each LM386. This configures the amplifier in non-inverting mode, with all signal entering through pin 3.</p>
</div>
</div>
<div class="step">
<div class="step-num">8</div>
<div class="step-body">
<h4>Install the Volume Control Potentiometer</h4>
<p>The dual-gang potentiometer has six terminals (three per channel). Wire each gang as follows:</p>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:.5rem">
<li><strong>Terminal 1</strong> (left side) → connects to the input coupling capacitor.</li>
<li><strong>Terminal 2</strong> (center/wiper) → connects to pin 3 of the LM386 via a jumper wire.</li>
<li><strong>Terminal 3</strong> (right side) → connect to GND.</li>
</ul>
<p>This creates a variable voltage divider that attenuates the input signal before it reaches the amplifier.</p>
</div>
</div>
<div class="step">
<div class="step-num">9</div>
<div class="step-body">
<h4>Add Input Coupling Capacitors</h4>
<p>Connect a <strong>10 µF electrolytic capacitor</strong> between the audio input source and each potentiometer's terminal 1. The positive lead (+) faces the audio jack side; the negative lead (−) connects to the pot. This blocks any DC offset from your audio source.</p>
</div>
</div>
<div class="step">
<div class="step-num">10</div>
<div class="step-body">
<h4>Connect the Audio Input Jack</h4>
<p>Wire your 3.5 mm TRS jack as follows:</p>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:.5rem">
<li><strong>Tip (Left channel)</strong> → left input coupling capacitor (+) lead.</li>
<li><strong>Ring (Right channel)</strong> → right input coupling capacitor (+) lead.</li>
<li><strong>Sleeve (Ground)</strong> → GND rail.</li>
</ul>
</div>
</div>
<div class="step">
<div class="step-num">11</div>
<div class="step-body">
<h4>Add Output Coupling Capacitors</h4>
<p>Connect a <strong>220 µF electrolytic capacitor</strong> from <strong>pin 5 (output)</strong> to each speaker's positive terminal. The positive lead (+) connects to pin 5; the negative lead (−) goes to the speaker. This blocks the DC bias voltage (~4.5 V at rest) from reaching the speaker coil.</p>
<div class="callout danger" style="margin-top:.5rem">🚫 Never connect a speaker directly to pin 5 without this capacitor! The LM386's output sits at approximately half of V<sub>CC</sub> (≈4.5 V DC) when idle — this will overheat and potentially destroy your speaker.</div>
</div>
</div>
<div class="step">
<div class="step-num">12</div>
<div class="step-body">
<h4>Connect the Speakers</h4>
<p>The other side of each speaker (the terminal not connected to the output capacitor) goes to GND. If you're using binding posts or terminal blocks, mount them on the breadboard and connect:</p>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:.5rem">
<li><strong>Speaker +</strong> → output coupling capacitor (−) lead.</li>
<li><strong>Speaker −</strong> → GND rail.</li>
</ul>
</div>
</div>
<div class="step">
<div class="step-num">13</div>
<div class="step-body">
<h4>Connect the Power Supply</h4>
<p>Finally, connect your 9 V battery (or DC power supply):</p>
<ul style="padding-left:1.5rem;color:var(--muted);margin-bottom:.5rem">
<li><strong>Battery + (red)</strong> → +VCC rail.</li>
<li><strong>Battery − (black)</strong> → GND rail.</li>
</ul>
<p><em>Do not connect power yet — complete the verification steps below first!</em></p>
</div>
</div>
<div class="callout success">
<strong>✅ Assembly Complete!</strong> Before powering up, carefully review every connection against the schematic and breadboard diagram. Then proceed to the testing section.
</div>
</section>
<!-- ═══════════════ SECTION 7: TESTING & TROUBLESHOOTING ═══════════════ -->
<section id="testing">
<h2>Testing & Troubleshooting</h2>
<h3>Pre-Power Checklist</h3>
<div class="card">
<ol style="padding-left:1.5rem;color:var(--muted)">
<li><strong>Visual inspection:</strong> Go through every connection on the breadboard and compare it to the schematic. Check that no wires are touching adjacent pins unintentionally.</li>
<li><strong>Capacitor polarity:</strong> Verify every electrolytic capacitor has the longer lead (+) toward the higher voltage side. Use your multimeter in diode mode if unsure — probe the positive lead first; a good cap will show OL (open loop), then slowly rise.</li>
<li><strong>Continuity check:</strong> Set your multimeter to continuity/ohms mode. Check that pin 4 of each LM386 connects to GND, and pin 7 connects to +VCC. There should be no short between VCC and GND (reading should be OL / infinite).</li>
<li><strong>IC orientation:</strong> Confirm the notch on each LM386 faces left, so pins are numbered correctly.</li>
</ol>
</div>
<h3>Power-Up Test</h3>
<div class="card">
<ol style="padding-left:1.5rem;color:var(--muted)">
<li><strong>Connect power with volume at minimum.</strong> Turn the potentiometer fully counter-clockwise (minimum volume) before applying power.</li>
<li><strong>Measure output DC voltage.</strong> With no audio signal, use your multimeter to measure the voltage at pin 5 of each LM386. It should read approximately <strong>V<sub>CC</sub> / 2 ≈ 4.5 V</strong>. If it reads near 0 V or near 9 V, there's a problem.</li>
<li><strong>Check for excessive heat.</strong> Touch the LM386 (briefly!). It should be warm but not hot after 10 seconds. If it's too hot to touch, disconnect power immediately — you likely have a short circuit or incorrect wiring.</li>
</ol>
</div>
<h3>Audio Test</h3>
<div class="card">
<ol style="padding-left:1.5rem;color:var(--muted)">
<li><strong>Connect your audio source</strong> via the 3.5 mm jack.</li>
<li><strong>Play a track at moderate volume</strong> on your source device.</li>
<li><strong>Slowly turn up the potentiometer.</strong> You should hear amplified stereo sound from both speakers.</li>
<li><strong>Test each channel independently:</strong> Play a left-only or right-only test tone to verify proper stereo separation.</li>
</ol>
</div>
<h3>Common Problems & Fixes</h3>
<div class="trouble-item">
<h4>No sound from either speaker</h4>
<p><strong>Cause:</strong> Power not connected, volume at minimum, or audio source muted.<br>
<strong>Fix:</strong> Verify +9 V is present on the VCC rail with a multimeter. Turn up the potentiometer. Check that your audio source is outputting sound (test headphones directly).</p>
</div>
<div class="trouble-item">
<h4>Loud buzzing or humming</h4>
<p><strong>Cause:</strong> Ground loop between audio source and amplifier, or missing decoupling capacitors.<br>
<strong>Fix:</strong> Ensure the audio jack sleeve is connected to GND. Verify both 100 nF decoupling capacitors are installed. Try a different audio cable.</p>
</div>
<div class="trouble-item">
<h4>Distorted or clipped sound</h4>
<p><strong>Cause:</strong> Input signal too strong for the gain setting, or power supply voltage too low.<br>
<strong>Fix:</strong> Reduce volume on your audio source. If using a battery, check that it's fresh (a weak 9 V battery may sag under load). You can also remove the gain capacitor (pins 1–8) to drop gain from 200× to 20×.</p>
</div>
<div class="trouble-item">
<h4>Only one channel works</h4>
<p><strong>Cause:</strong> Loose connection on the non-working channel, or IC inserted backwards.<br>
<strong>Fix:</strong> Check all connections on the silent channel. Verify pin 7 has +VCC and pin 4 has GND. Measure DC voltage at pin 5 — it should be ≈4.5 V.</p>
</div>
<div class="trouble-item">
<h4>LM386 gets very hot</h4>
<p><strong>Cause:</strong> Speaker connected directly to output (no coupling capacitor), short circuit, or output pin grounded.<br>
<strong>Fix:</strong> Disconnect power immediately. Check that the 220 µF output coupling capacitor is correctly installed between pin 5 and the speaker. Verify no wire shorts pin 5 to GND.</p>
</div>
<div class="trouble-item">
<h4>Popping or clicking when turning volume</h4>
<p><strong>Cause:</strong> Normal behavior with carbon-track potentiometers at high gain.<br>
<strong>Fix:</strong> Use a higher-quality potentiometer (cermet or conductive plastic). This is cosmetic and doesn't indicate a circuit problem.</p>
</div>
<h3>Performance Notes</h3>
<div class="card">
<ul style="padding-left:1.5rem;color:var(--muted)">
<li><strong>Maximum output power:</strong> ≈250 mW per channel into 8 Ω at 9 V supply (theoretical; real-world is closer to 100–150 mW).</li>
<li><strong>Total harmonic distortion (THD):</strong> Typically <0.7% at rated output.</li>
<li><strong>Frequency response:</strong> 20 Hz – 20 kHz (suitable for full-range audio).</li>
<li><strong>Battery life:</strong> A standard 9 V alkaline battery (~500 mAh) will last approximately 3–5 hours at moderate volume.</li>
<li><strong>To increase power:</strong> Use a higher supply voltage (up to 15 V max for the LM386) and/or lower impedance speakers (down to 4 Ω, but monitor IC temperature).</li>
</ul>
</div>
<div class="callout success">
<strong>🎉 Congratulations!</strong> You've built a fully functional stereo audio amplifier from scratch. With two LM386 chips, a handful of passive components, and no soldering, you now have a working breadboard amplifier that can drive real speakers. Experiment with different gain settings, try adding bass boost circuits, or transfer the design to a perfboard for a permanent build.
</div>
</section>
</div><!-- /.container -->
<footer>
<p>Stereo Audio Amplifier Breadboard Build Guide — LM386 Dual-Channel Design</p>
<p style="margin-top:.25rem">Built for learning and experimentation. Always follow safety guidelines when working with electronics.</p>
</footer>
</body>
</html>
<!-- agent-meta {"model":"qwen3.6-27b-mtp","provider":"lmstudio","persona":"full","sessionId":"065cfd20-dd86-48a1-b5be-7bae759b8ac9","tokensIn":128765,"tokensOut":27423,"tokensTotal":156188,"turns":5,"toolCalls":4,"failedToolCalls":0,"timestamp":"2026-07-29T14:33:55.739Z"} -->