YouTube Video Series

I have several other video series on my YouTube channel: DeepBlueHarp 
The following are the links to the playlists followed by a subject index.

Harmonics

    Harmonic Distortion: Introduction
    Harmonic Distortion V2: Harmonic Generation 
    Harmonic Distortion Video 3: Design Issues
    Harmonic Distortion Video 4: Linear, Ultra-Linear and Tubes vs Transistors
    Harmonic Distortion, Video 5: Vg, The Grid Voltage Signal
    Harmonic Distortion, Video 6: gm, Transconductance Curve
    Harmonic Distortion, Video 7: The 2nd harmonic
    Harmonic Distortion, Video 8: Self-Rectification and Grid Leak Bias
    Harmonic Distortion, Video 9: The 3rd Harmonic
    Harmonic Distortion, Video 10: Why I don't care about the 4th harmonic.
    Harmonic Distortion, Video 11 "Key Points to Espley's Method"
    Harmonic Distortion, Video 12: "Espley's Linear Transformation"
    Harmonic Distortion, Video 13: "Espley's Expansion of Frequency Terms Using Pascal's Triangle"
    Harmonic Distortion, Video 14: "Espley's 2nd Harmonic"
    Harmonic Distortion, Video 15: "Espley's 4th Harmonic"
    Harmonic Distortion, Video 16: "Espley's 6th Harmonic"

Microphone Cupping

    Microphone Cupping Data, Part 1: "Introduction & Test Setup"
    Microphone Cupping Data Part 2: "Frequency Response Curves"
    Microphone Cupping Data, Part 3: " Sound Pressure Level"

Tremolo Operation

    Tremolo (TREM1) Signal Analysis of Pumping, Knocking, Ticking
    Tremolo (TREM2) Stopping the Tick, Using a Long-Tail Resistor, Speed Only Configuration
    Tremolo (TREM3) Stopping the Tick Using a Long-Tail Resistor, Intensity/Depth Configuration
    Tremolo (TREM4) EMF

"Variac"

VARIAC® is a registered US trademark of General Radio (in 2004 Instrument Service Equipment obtained the trademark for their equivalent product). The unit in my “Variac” video series is a similar unit and is commonly and mistakenly called a VARIAC (it is not). VARIAC sells a UL LISTED product. Do not operate any unit that does not have a National Testing Certification (NTC) mark such as UL, CSA, CE, or SA; or until you have the unit inspected for safety and code compliance. For clarity, the term VARIAC will refer to the manufacturer who owns the trademark and “Variac” (in quotes) for units that are similar. "Similar" will be a limited definition of: a transformer coil with a shared core, two fixed taps, and a variable center tap.

If you purchased one of the common "Variacs" that are red, they are manufactured by China and they are poorly built. First of all, it is not "Made in the USA" and that is false advertising. And these units are not UL Listed. This brand new unit failed and could have electrocuted me. I discovered inside was not code compliant and unsafe. There were many large loose solder drips (one was 1/4" in diameter) and wire jacketing pieces that were not removed after stripping the wire ends. This video series is what I did to make the "Variac" safer. Before operating the unit have it checked by a technician that is familiar the design of an autotransformer. 

 Subjects in the "Variac" playlist: 
    Variac
    "Variac" Brush Replacement and Retrofit
    "Variac" Brush Modification
    Variac Brush Alignment and Adjustment
    Ground Wire Design and Warning
    "Variac" Fuse Location and 2 Rules for Fuses
    Taps and Shielding
    Variac Rewired
    Checkout and Load Test 

 Tone Stack 

    TS1 Tone Stack Concepts
    TS2: Big Muff Tone Stack
    TS3 Methodology for Designing a Bright Capacitor
    TS4 Fender Tone Stack
    TS4a Fender Tone Stack Curves
    TS5 Bright Cap for Fender
    TS7 Princeton Tone Stack
    TS6 Premier Twin 8R Tone Stack 
    TS8 Twin-t notch filter
    TS9 Switching Tone Capacitors
    How Component Tolerances Affect Tonestacks