1. The Approach to Hi-Fi
The background of audio. Early advances. Triode versus pentode. Use of
positive and negative feedback.
2. Special Output Stages
Push-pull triodes. Tetrode or pentode. Ultra-linear. Grid drive. Effective
plate resistance. Cathode followers. Unity coupling. Modified ultra-linear.
Circlotron. Comparative qualities of output circuits.
3. Feedback and Damping
Loop gain and feedback factor. Negative and positive feedback. Cyclic
blocking. Avoiding overload blocking. Effects of feedback. Stability of
gain. Frequency response. Output impedance. Stability margins. Phase
margin. Gain Margin. Maximal flatness. Loading. Multiple-loop feedback.
Phase correction methods. Variable damping.
4. Inverter and Driver Stages
Direct-couuled transformers. Parallel-fed transformers. Tapoed af choke.
Split-load inverter. Paraphase. Output-coupled paraphase. Floating para-
phase. Long-tailed inverter. Cross-coupled inverter. Extra push-pull
drive stages. Positive feedback drive. Comparative qualities of phase
inverters.
5. Input Stages
Thermal noise. Noise voltages. Hum. Cable microphony. Microphonic
tubes. Distortion. Bootstrap pentode input. Transistors.
6. Matching
Input circuits. Output circuits. Minimum distortion. Transistors.
7. Equalization
Phono and tape equalization. Disc and tape standards. Methods of equal-
ization. Passive equalizer. Separate sections. Feedback type. Single triode
stage. Single pentode stage. Two-triode stages. Relative properties of
equalizer circuits.
8. Speaker Distribution and Crossovers
Kinds of reproducer. Intermodulation. Multiple-unit speakers. Peaky
highs. Balance. Crossovers. Inductors and capacitors. Channel separators.
Feedback separators.
9. Loudness and Volume Controls
Fletcher-Munson Curve. Position of controls in circuit. Circuits. Con-
tinuously variable or stepped. Feedback types.
10. Tone Controls
Tone-control functions. Response. Simple step circuits. Practical con-
siderations. Feedback and peaking types. Variable-slope rolloff.
11. Overall View of Hi-Fi
Index