High-End Tube Amplifiers: Theory, Practice, and Construction

This document provides a comprehensive guide to the theory, practice, and construction of high-end tube amplifiers. It covers essential concepts, component selection, circuit designs, and measurement techniques for audio enthusiasts and DIY constructors.

Introduction

This section introduces the fundamental concepts of HiFi amplifiers, including their definitions, tasks, and the required amplifier power.

Definition and Tasks of a HiFi Amplifier

Explains what a HiFi amplifier is and its role in an audio system.

How Much Amplifier Power is Needed?

Discusses the factors influencing the required amplifier power for optimal audio performance.

1 - Theory

This section delves into the theoretical underpinnings of audio amplification.

1.1 - The dB Calculation

Explains the decibel (dB) scale and its application in audio measurements.

1.2 - Linear Amplifiers

Discusses the characteristics and operation of linear amplifiers.

1.3 - Non-linear Amplifiers

Explores the behavior and implications of non-linear amplification.

1.4 - Power Output Stages

Details the design and function of power output stages in amplifiers.

1.5 - Transistor Output Stages

Covers the specifics of transistor-based output stages.

1.6 - Tube Output Stages

Focuses on the design and operation of vacuum tube output stages.

1.7 - The PPP Output Stage

Explains the Parallel-Push-Pull (PPP) amplifier configuration.

1.8 - Interactions Between Output Stage and Loudspeaker

Discusses the crucial relationship and interactions between the amplifier's output stage and the connected loudspeaker.

1.9 - Power Supplies

Covers the theory and design of power supply units for amplifiers.

1.10 - Connecting System Components, Matching, and Level Relationships

Provides guidance on connecting audio components and managing signal levels.

1.11 - Typical Output Stages and Their Behavior

Analyzes the characteristics of various common output stage designs.

1.12 - Hum Problems and Their Causes

Addresses common hum issues in amplifiers and their underlying causes.

1.13 - Tube or Transistor - That is the Question

Compares and contrasts the use of tubes versus transistors in amplifier design.

Component Selection

1.14 - Resistors

Details the selection and use of resistors in amplifier circuits.

1.15 - Capacitors

Covers the selection and application of capacitors.

1.16 - Potentiometers

Discusses potentiometers for volume and tone control.

1.17 - Connectors and Signal Switching

Explains the importance of connectors and signal switching mechanisms.

1.18 - Active Components

Provides an overview of active electronic components used in amplifiers.

1.19 - Mains Transformers

Details the selection and function of mains transformers.

1.20 - Smoothing Chokes

Explains the role of smoothing chokes in power supply filtering.

1.21 - Transformers

Covers various types of transformers used in audio circuits.

1.22 - Printed Circuit Boards (PCBs)

Discusses the use and considerations for PCBs in amplifier construction.

1.23 - Solder

Provides information on solder types and their application.

1.24 - Wiring and Construction Tips

Offers practical advice on wiring and general construction techniques.

2 - Practice

This section focuses on the practical implementation of amplifier circuits.

Power Supplies

2.1 - DC Heaters

Details various methods for providing DC heater voltage for tubes.

2.1.1 - Heater with 78xx

Circuit design using 78xx voltage regulators for heater supply.

2.1.2 - Heater with LM317/LT1085

Circuit design using LM317/LT1085 for heater supply.

2.1.3 - Heater 723, 1 x FET, 3 A

Design for a 3A heater supply using the 723 regulator and one FET.

2.1.4 - Heater 723, 2 x FET, 6 A

Design for a 6A heater supply using the 723 regulator and two FETs.

2.1.5 - Heater 723, 2 x FET, 10 A

Design for a 10A heater supply using the 723 regulator and two FETs.

2.1.6 - Heater 6.3 VAC to 6.3 VDC

Circuit for converting 6.3V AC heater supply to 6.3V DC.

2.1.7 - ±15 V

Design for a ±15V power supply.

2.1.8 - ±15 V with Mains Transformer

Design for a ±15V power supply using a mains transformer.

2.2 - High Voltage Power Supplies

Covers various high voltage power supply designs for tube amplifiers.

2.2.1 - Stabilized High Voltage for Tube Preamplifiers with Low Current Requirements

Design for a low-current stabilized high voltage supply for preamplifiers.

2.2.2 - Stabilized High Voltage for Preamplifiers with Medium Current Requirements

Design for a medium-current stabilized high voltage supply for preamplifiers.

2.2.3 - Stabilized High Voltage for Preamplifiers and Smaller Single-Ended Class A Output Stages

Design for a high voltage supply suitable for preamplifiers and small single-ended Class A stages.

2.2.4 - High Voltage with CLC Filtering

Implementation of a high voltage supply using CLC (Capacitor-Inductor-Capacitor) filtering.

2.2.5 - High Voltage with CLC Filtering for Stereo Output Stages

CLC filtered high voltage supply specifically for stereo output stages.

2.2.6 - CLCLC Filtering for Single-Ended Class A Output Stages

Advanced CLCLC filtering for single-ended Class A output stages.

Output Stages

2.3 - Single-Ended Class A Output Stages

Details various single-ended Class A amplifier designs.

2.3.1 - Compact Stereo Single-Ended Class A Output Stage, Also Suitable for Headphone Operation

A compact stereo amplifier design that can also be used for headphones.

2.3.2 - Output Stage with EF 86 and EL 84 T in Triode Mode

Amplifier circuit using EF 86 and EL 84 T tubes in triode configuration.

2.3.3 - Output Stage with ECC 99 and EL 156 in Triode and Pentode Mode

Amplifier circuit using ECC 99 and EL 156 tubes in both triode and pentode modes.

Output Stage Variants with EL 34, KT 88, KT 120, and ECC 99

Discusses variations of output stages using these specific tubes.

2.3.4 - Output Stage with PCL 86 and 2 x EL 34 or 2 x KT 88

Amplifier circuit using PCL 86 with either two EL 34 or two KT 88 output tubes.

2.3.5 - Output Stage with PCL 86 and 6C33

Amplifier circuit using PCL 86 with a 6C33 tube.

2.3.6 - Output Stage with PCL 86 and 300 B

Amplifier circuit using PCL 86 with a 300B tube.

2.4 - Push-Pull Class AB Output Stages

Details various push-pull Class AB amplifier designs.

2.4.1 - Triode Output Stage with ECC 832 and ECC 99 with 3.5 W

A 3.5W triode amplifier using ECC 832 and ECC 99 tubes.

2.4.2 - Output Stage with 4 x EL 84 (T) in Triode and Pentode Mode

Amplifier circuit using four EL 84 (T) tubes in triode and pentode configurations.

2.4.3 - Output Stage with 2 x EL 34 and 2 x KT 88

Amplifier circuit using two EL 34 and two KT 88 tubes.

2.4.4 - Push-Pull Class AB Tube Output Stages with 2 and 4 Output Tubes and Output Powers Between 32 W and 210 W

Covers push-pull Class AB tube amplifiers with 2 or 4 output tubes, offering power outputs from 32W to 210W.

2.4.5 - Output Stage with 2 x EL 156

Amplifier circuit using two EL 156 tubes.

2.4.6 - Output Stage with 2 x 6C33

Amplifier circuit using two 6C33 tubes.

2.5 - Parallel-Push-Pull Output Stages

Details various Parallel-Push-Pull (PPP) amplifier designs.

2.5.1 - PPP Output Stage with 4 x EL 84 (T)

PPP amplifier circuit using four EL 84 (T) tubes.

2.5.2 - PPP Output Stages with 2 x EL 34, 2 x KT 88, and 2 x KT 120

PPP amplifier circuits using pairs of EL 34, KT 88, or KT 120 tubes.

2.5.3 - PPP Output Stage with 4 x EL 34 and 4 x KT 88

PPP amplifier circuit using four EL 34 and four KT 88 tubes.

2.5.4 - High Voltage Power Supply for PPP Output Stages

Design for a high voltage power supply specifically for PPP amplifier configurations.

Preamplifiers

2.6.1 - Line Preamplifier with PCL 86

Line preamplifier circuit using the PCL 86 tube.

2.6.2 - Line Preamplifier with ECC 99 and EL 84 (T), Mono Configuration

Mono line preamplifier circuit using ECC 99 and EL 84 (T) tubes.

2.6.3 - Tone Controls in Tube Technology

Discussion of tone control circuits implemented with vacuum tubes.

2.6.4 - Input Relay Board with 4 or 6 Inputs

Description of an input selector board using relays, with 4 or 6 inputs.

2.6.5 - Input Relay Board with 5 Inputs and Preamplifier

Description of an input selector board with 5 inputs, including a preamplifier stage.

2.6.7 - Combinations

Explores various combinations of preamplifier and input selector circuits.

2.7 Equalizer Preamplifiers

Details designs for phono/equalizer preamplifiers.

2.7.1 - Equalizer Preamplifier with the PCL 86 Tube

Phono preamplifier circuit using the PCL 86 tube.

2.7.2 - Equalizer Preamplifier with Semiconductors

Phono preamplifier circuit utilizing semiconductor components.

2.7.3 - CD Filter

Circuit design for a CD filter.

Circuits for Special Applications

2.8.1 - Idle Protection for Tube Amplifiers

Circuit to protect tube amplifiers during idle operation.

2.8.2 - Inrush Current Limiter

Circuit designed to limit the inrush current when powering on.

2.8.3 - Mains Filter

Description of a mains filter circuit for noise reduction.

2.8.4 - Rectifier Circuit for VU Meter

Rectifier circuit specifically for powering a VU meter.

2.8.5 - Measurement Filter for Stray and Noise Voltage Measurements

Filter circuit for measuring stray and noise voltages.

3 - Construction, Commissioning, and Measurement Technology

This section covers the practical aspects of building, testing, and measuring amplifiers.

3.1 - Construction and Commissioning

Guidance on the assembly and initial setup of amplifier projects.

3.2 - Power

Methods for measuring amplifier power output.

3.3 - Frequency Response

Techniques for measuring the frequency response of an amplifier.

3.4 - Damping Factor

Explanation and measurement of the damping factor.

3.5 - Input Resistance

Methods for measuring the input resistance of an amplifier.

3.6 - Noise Measurements

Techniques for performing noise measurements on amplifiers.

3.7 - Distortion Factor

Methods for measuring the total harmonic distortion (THD) or distortion factor.

3.8 - Channel Crosstalk

Techniques for measuring channel crosstalk in stereo amplifiers.

3.9 - Transformer Testing

Methods for testing the performance of transformers.

3.10 - Final Considerations

Concluding remarks and final thoughts on amplifier projects.

4 - Information, Datasheets, Connection Pinouts

This section provides supplementary information, datasheets, and connection diagrams.

4.1 - Mains Transformers

Information and specifications for mains transformers.

4.2 - Smoothing Chokes

Specifications for smoothing chokes.

4.3 - Output Transformers

Specifications and data for output transformers.

4.4 - Input Transformers

Specifications and data for input transformers.

4.4.1 - Input Transformer E-1220

Specific data for the E-1220 input transformer.

4.4.2 - Moving-Coil Transformer R-110

Specific data for the R-110 moving-coil transformer.

4.5 - Tube Data and Socket Pinouts

Provides data sheets and pinout diagrams for various vacuum tubes.

4.6 - Notes

General notes and additional information.

5 - Layouts

This section contains physical layouts for circuit construction.

Index

A comprehensive index is provided for easy navigation.