Audio Amplifier Design & Repair Course

Lesson 1 • Essential Electrical Concepts Review

Covers voltage, current, resistance, and power relationships critical to amplifier analysis. Establishes the quantitative baseline every subsequent chapter depends on.

Lesson 2 • Reading and Interpreting Schematics

Teaches standard schematic symbols, reference designators, and signal-flow conventions. Enables accurate circuit tracing before any hands-on work begins.

Lesson 3 • Amplifier Classifications and Topologies

Surveys Class A, B, AB, D, and other operating classes by efficiency and linearity. Provides the taxonomy students use to identify any amplifier design encountered in practice.

Lesson 4 • Audio Signal Characteristics

Defines frequency range, amplitude, and waveform properties of audio signals. Connects signal characteristics to amplifier performance requirements.

Lesson 1 • Biasing Techniques for Stable Operation

Presents fixed bias, self-bias, and cathode bias methods with thermal stability analysis. Stable bias is prerequisite to low-distortion amplifier performance.

Lesson 2 • MOSFET and JFET Characteristics

Covers enhancement and depletion mode FETs, transfer curves, and gate drive requirements. Prepares students for modern solid-state power stage design.

Lesson 3 • Vacuum Tube Fundamentals

Introduces triode, pentode, and beam power tube operation for audio applications. Equips students to service vintage and boutique tube amplifiers confidently.

Lesson 4 • Bipolar Junction Transistor Operation

Explains NPN and PNP transistor physics, regions of operation, and small-signal models. Directly supports biasing and gain calculations in later design chapters.

Lesson 1 • Filter Capacitor Sizing and Ripple

Calculates bulk capacitance needed to meet ripple voltage specifications under load. Ripple directly couples into the audio path as hum if undersized.

Lesson 2 • High-Voltage Tube Supply Design

Addresses B+ supply design, bleeder resistors, and slow-start circuits for tube amplifiers. High-voltage discipline prevents component failure and operator injury.

Lesson 3 • Linear Voltage Regulator Design

Designs series-pass and shunt regulators for low-noise preamplifier supply rails. Regulated rails dramatically reduce power supply rejection requirements on gain stages.

Lesson 4 • Transformer Selection and Rectification

Covers VA rating, secondary voltage, and full-wave bridge rectifier design. Correct transformer sizing prevents saturation and excessive regulation drop.

Lesson 1 • Differential and Long-Tail Pair Stages

Introduces differential amplifier topology used in op-amp input stages and feedback loops. Common-mode rejection ratio and tail current source design are emphasised.

Lesson 2 • Coupling and Bypass Capacitor Design

Determines capacitor values for target low-frequency cutoff and inter-stage coupling. Correct capacitor sizing prevents bass rolloff and unwanted signal attenuation.

Lesson 3 • Emitter Follower and Source Follower Buffers

Covers unity-gain buffer stages used for impedance transformation between sections. Buffers prevent gain loss when driving low-impedance loads or cables.

Lesson 4 • Common-Emitter and Common-Source Stages

Analyses the most widely used gain configurations for voltage amplification. Gain and impedance formulas derived here apply directly to multi-stage designs.

Lesson 1 • Noise Sources and Noise Figure

Identifies thermal, shot, and flicker noise sources and calculates equivalent input noise. Low-noise design techniques are applied to preamplifier and phono stages.

Lesson 2 • Negative Feedback Principles

Derives the closed-loop gain equation and quantifies distortion reduction with feedback. Feedback is the central tool for achieving professional amplifier performance.

Lesson 3 • Oscillation Prevention and Compensation

Presents dominant-pole, lead, and lag compensation methods to stabilize feedback loops. Students apply these techniques to both solid-state and tube amplifier designs.

Lesson 4 • Stability Analysis and Phase Margin

Uses Bode plots to assess gain margin and phase margin for unconditional stability. Insufficient phase margin causes oscillation, making this analysis mandatory.

Lesson 1 • Power Output and Efficiency Measurement

Determines continuous and peak output power into resistive and reactive loads. Efficiency measurement guides thermal design and power supply sizing decisions.

Lesson 2 • Noise Floor and Dynamic Range Testing

Measures A-weighted noise, dynamic range, and signal-to-noise ratio under standard conditions. These metrics determine suitability for professional and high-fidelity applications.

Lesson 3 • Distortion Measurement: THD and IMD

Measures total harmonic distortion and intermodulation distortion using audio analyzers. THD and IMD figures are the primary indicators of amplifier linearity.

Lesson 4 • Oscilloscope Use in Amplifier Testing

Covers probe compensation, triggering, and waveform capture for audio signal analysis. The oscilloscope is the primary diagnostic tool for waveform-level fault finding.

Lesson 1 • Protection Circuits for Output Stages

Designs short-circuit, over-current, and DC-offset protection to safeguard speakers and devices. Protection circuits must respond faster than thermal damage can occur.

Lesson 2 • Thermal Management and Heat Sink Design

Calculates junction-to-ambient thermal resistance and selects heat sinks for safe operation. Thermal failure is the leading cause of output device destruction in power amplifiers.

Lesson 3 • Push-Pull Output Stage Design

Analyzes complementary and quasi-complementary push-pull topologies for solid-state amplifiers. Push-pull operation cancels even-order harmonics and doubles output swing.

Lesson 4 • Output Transformer Design for Tube Amps

Covers impedance transformation, primary inductance, and leakage reactance in output transformers. The output transformer is the most critical passive component in a tube amplifier.

Lesson 1 • Repair Techniques and Post-Repair Verification

Covers soldering, desoldering, PCB trace repair, and full post-repair performance verification. Every repaired amplifier must meet original specifications before returning to service.

Lesson 2 • Component Testing and Verification

Tests resistors, capacitors, inductors, diodes, and transistors in-circuit and out-of-circuit. Accurate component verification prevents re-installation of marginal parts.

Lesson 3 • Common Solid-State Amplifier Failures

Catalogs typical BJT and MOSFET output stage failures, bias drift, and driver faults. Pattern recognition of common failures accelerates diagnosis in production repair environments.

Lesson 4 • Tube Amplifier Fault Diagnosis

Covers weak tubes, bias drift, output transformer faults, and rectifier failures in tube amps. Tube amplifiers present unique high-voltage hazards during live fault diagnosis.