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
Fender Circuit Evolution
Marshall
Traynor Amps: More than Just Copies
Other Manufacturers
Garnet
Ampeg
Mesa-Boogie
Hiwatt
Wizard
Saldano
Peavey
Tube Works
ADA
Carvin
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
Rectifiers
Switching Between Tube & Metal Rectifiers
Adding Cooling Fans
Chapter 3: Vacuum Tubes
Early History
Vacuum Tube Diodes
Vacuum Triodes
Tetrodes
Pentodes
Beam Power Pentodes
Multi-Element Tube Standards
Multiple Tubes
Chapter 4: Preamp Basics
Voicing
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
Sustain
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
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
Channel-Switching
Channel-Chaining
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
Phase-Splitters
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
6L6GC-5881
6V6GTA
6CA7-EL34
6BQ5-EL84
7027A
8417
6550A-KT88
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
Background
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
J-fets
Mosfets
CMOS Switches
LDRs
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
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
