The Ultimate Tone

Table of Contents

Chapter 1: System Overview
System Contexts 
      System Growth
      Sonic Perceptions
      Combo Amps versus Stacks
      Mono versus Stereo Systems
      Guitar-Centred versus Band-Oriented Systems
      Equipment Evaluations
Modification Platform Candidates
      Fender Circuit Evolution
Traynor Amps: More than Just Copies
Other Manufacturers
      Tube Works
      Groove Tubes
Overall Modification Platform Choices

Chapter 2: Power Supplies & Grounds
Filament Supplies
Plate Supplies
Power Supply Energy Storage
Choke Filters
Bias Supplies
DC Grounds
AC Grounds
Power Supply Modifications
Power Supply Decoupling
Adding Regulators
Master Regulator with Local Supply Decoupling, and Parallel Regulators
Cascaded Regulators
Filament Supply Mods
      Shielding the Filament Wiring
      DC Filament Operation
      Soft-Start Filament Supply Rectifiers
      Switching Between Tube & Metal Rectifiers
Adding Cooling Fans

Chapter 3: Vacuum Tubes
Early History
Vacuum Tube Diodes
Vacuum Triodes
      Beam Power Pentodes
Multi-Element Tube Standards
Multiple Tubes

Chapter 4: Preamp Basics
Basic Gain Stages
RC Time Constants and Equalization
The Mu-Amp
Noise: What It Is and Where It Comes From
      Noise in Tubes
      Signal-to-Noise Ratios and Dynamic Range
      AC Line-Related Noise
      Confining Magnetic Fields
      Ground Noise and Ground Loops
      Ground Lift

Chapter 5: Preamp Mods
      Guitar Sustain
      Amp Sustain
      Clean Sustain
      Distorted Sustain
Traditional Overdrive Architecture
Master Volume Amps versus Non-Master Volume Amps
      Non-Master Distortion Generation
      Master Volume Distortion Generation
      Master Volume Placement
      Conventional Master Volume
      Multiple Channel Master Volume
      Power Amp Master Volumes
      Typical Power Amp Master Volume Installations
Distortion Generating Techniques
Diode Bouncing
      Semiconductor Diodes
      Vacuum Tube Diodes
      Using Solid-State Diodes to Mimic Vacuum Diodes
      Variable Compliance and Bounding


Chapter 5 cont'd:
Multi-Tonal and Multi-Channel Gain Architecture
      Multi-Channel Topologies
Standard Preamp Analysis
      Dual-Volume Topology
      Standard Fender Topology
      Standard Marshall Topology
      London Power Standard Preamp
Alternative Topologies
      Tapped Gain Block
      Stackable Gain Topology
      Parallel-Drive Topology
Modifications for Fender Preamps
      Equal Channel Weighting
Modifications for Marshall Preamps
      Adding a Master Volume without Losing the Dual-Volume Input
      Input Switching for the 800-Series
      Producing More Distortion without Gain Increase
      More Distortion via Gain Increase
London Power Standard Circuit Variations
      Most Popular Variation, with Lead Boost
      Ultra-Low-Noise Variation
Poor Man's Overdrive
Tweed Mixer
Parallel-Drive Variations
Bass Guitar Preamps
Acoustic Preamps

Chapter 6: Power Amps
Power Gain in Preamps
Power Amp Topologies
      Single-Ended Power Amps
      Double-Ended Power Amps
Classes of Operation
      Class-A Operation
      Class-AB1 Operation
      Class AB2 Operation
Bias Methods
      Cathode Bias
      Fixed Bias
      Generating a Bias Supply
      Concertina Splitter
      Phase-Inverter Splitter
      Paraphase Boost Stages
      Differential Splitter
      Differential Input-Splitter
      Gain Compensation in the Guitar PA Front-End

Closing the Loop Around the Power Amp
Presence Controls in Power Amps
      Changing the Presence Depth
Resonance Controls
Advanced Resonance and Presence Methods
      Ideal Pre-Resonance Method
Output Transformers
      Power Output versus Tube Complement and Load Impedance
      Transformer Balance and Tube Matching
Bias Adjustments in Fixed-Bias Amps
Bias Adjustments in Cathode-Bias Amps
Feedback and Hum Rejection
      Ultralinear Connections
      Cathode-Coupled Outputs
Power Tubes
      General Overview of Power Tube Compatibility
      Never, Never ...
      Relative Reliabilities
Fender versus Marshall Reliability
      The Traynor Method
Power Reduction Methods
      Triode-Pentode Switching
      Mixing Triode Operation with Ultralinear Operation
      Mixing Output Tube Types
Gain Reduction in the Front-end
      Variable gm in the Diff-Amp
      Error Signal Cancellation
      Voltage Reduction to the Front-end
Mixing Classes of Operation
Output Tube Switching
      Cathode Switching as a Stand-By
      Automated Cathode Switching
      Protecting the Output Stage
      Passive Current Sensing
The VOX AC30 Myth
"Thunderous Smooth"


Chapter 7: Effects Loops
      The Essential Loop
Buffered Loop
      First Approximation Buffer: Self-Bias
      Second Approximation Buffer: Current-Source Biasing
Line Level versus Guitar Level Loops
      Return-Level Boosters
      Noise in the Return Boost Amplifier
The Best All-Tube Loop
Solid State Loops
      First Approximation Solid-state Loop ICs
Intuitive Approach to High-Voltage Discrete Buffers
Development of High-Voltage Solid-state Effects Loops
      Turning the Cascode into a Buffer
Cascode Op-Amp Development

Chapter 8: Reverbs
Spring Reverb Tanks
Reverb Integration Topologies
      Unitized Reverb Loop
      Parallel Internal-External Effects Loop
      Power Amp Fold-Back Reverb Loop
      Comparison of the Three Topologies
Dwell and Reverb Levels
Noise in the Reverb Loop
Specific Circuit Methods
      Tube Reverb Driver
      Solid-state Reverb Drivers
      Tube Reverb Return Circuits
      Solid-state Return Amps
      Solid-state Return Mixers
Complete Reverb Systems
      Standard Tube Reverb Loop
      Parallel Reverb-FX Loop
      Tube Power Amp Fold-Back Reverb Loop
      Standard Op-Amp Reverb Loop
      Power Amp Fold-Back Reverb Loop with J-fet Return
Other Reverb Considerations
Reverb Switching

Chapter 9: Switching Methods
Operator Requirements     
Switching Element Features
Ideal Switch Element Characteristics
      Real-Life Switch Element Characteristics
      Transistor Switches
         - BJTs
      CMOS Switches

Switching Topologies
      Series Switching
      Shunt Switching
      J-fet Series Switches
      J-fet Shunt Switches
      BJT Series Switches
      BJT Shunt Switches
      Mosfet Series & Shunt Switches
      CMOS Series & Shunt Switches
Shunt-Tee Switches
The Shunt Splitter
Zero-Signal Switching
      J-fet Zero-Signal Switch
      CMOS Zero-Signal Switching
      Mosfet Zero-Signal Switching       
      BJT Zero-Signal Switching
The Human Interface
      Electronic Isolation with Latching Interface Switches
      Controlling Relays
      Annunciation: Adding LEDs to Our Relay Circuits
      Multiple Switching
J-fets with Latching Switch Controls
      Generating a Negative Rail for the J-fet Gate
      Interfacing the J-fet with Latching Switches
      Creating a Double-Throw J-fet Switch
Annunciation: Adding LEDs to the J-fet Switch
      Single-Throw J-fet Switch with LEDs
      Double-Throw J-fet Circuits with LEDs
      Dual LED Annunciation
      Dual LED Annunciator with a Minor Simplification
      Dual Inboard LEDs with a Single Foot-Switch LED
BJTs with Latching Switch Controls
      Double-Throw BJT Switch
Annunciation: Adding LEDs to the BJT Controllers
      Single-Throw BJT with LEDs
      Double-Throw BJT with LEDs
CMOS with Latching Switches
      Single-Throw CMOS Switching
      Double-Throw CMOS Switching
Annunciation: Adding LEDs to CMOS Controllers
      Single-Throw CMOS with LEDs
      Double-Throw CMOS with LEDs
Non-Latching Foot-Switches
      Electronic Switches
      Discrete versus IC Flip-Flops
      CMOS versus Other IC Technologies
      A,B Selectors
      A,B,A+B Switching


Chapter 9 cont'd:
Annunciation: Adding LEDs to the Toggle Circuits
      Adding LEDs to the Foot-Switch
Two-Way Communication
      Alternate-Action Switches Used as Momentaries in 2-Way Foot-Controllers
Mixing Other Control Functions
      Reverb Switching
      Tremolo On-Off Switching
      Mute On-Off and Mute-Hold Switching
      Mute-Hold Circuits
      Mute On-Off Circuits
      Combining Mute-Hold and Mute On-Off Functions
Effects Loop Switching
      J-fet Ring Switching
Integrating the Switching and Audio Circuits
      Local Channel Switching
      Enhanced Local Switching with BJTs
      Switching Circuit Integration Repercussions
      Bright and Normal Channel Switching
      High-Low Switching in Marshalls
      Channel-Chaining in Fender Amps
Power Switching
      Triode-Pentode Switches
      Automating the Triode-Pentode Switch
      Output Tube Selection
      Automating the Output Tube Selector
      Speaker Selectors
      Mosfet Bilateral Switch for Speaker Selection
      Multiple Amps and Multiple Speakers
      Random Access Foot-Controllers
      Driving Bicolour LEDs

Appendix A:
Tube Data

Appendix B:
The Futterman Amp

Appendix C:
Hammond Transformer Information