Appendix A
Terminology
- Valve - same thing as a tube. Sometimes called a "thermionic valve." This is where the amplification of the signal occurs.
- Cap - capacitor. It is two metals or conductors separated by a non-conductor. They pass AC signal easier than DC signal. They will also store a charge and release it rapidly. Said another way, the capacitor will resist change in voltage. These are used in the tonestack and power supply as well as other parts of the circuit.
- Resistor - something that will impede the flow of electricity. These are used extensively through an amp's circuitry.
- Inductor - A spiral of copper (or other material) that will resist change in current. It will store energy in a magnetic field. Typically used in the power supply. Sometimes used in the tonestack and other parts of the circuit.
- Transformer - Two or more inductors with their magnetic fields coupled. A change in one inductor's voltage or current will be reflected onto the other. These are used in the power supply, reverb circuit, output section, and sometimes in the phase inverter.
- Variable resistor - rheostat. A resistor who's value can be changed.
- Potentiometer - Pot. A variable resistor that is center tapped. Can be wired as a variable resistor by connecting an outside lug to the center tap.
- Diode - a device that allows current to flow in only one direction.
- Triode (tube) - A tube consisting of a grid, anode (plate), and cathode. The 12AX7 is a dual triode, meaning there are two individual triodes within the tube.
- Tetrode (tube) - A tube consisting of a grid, anode (plate), cathode, and screen.
- Pentode (tube) - A tube consisting of a grid, anode (plate), cathode, screen, and suppressor. Most tubes considered to be tetrodes are actually pentodes with an internal connection between the suppressor and cathode.
- Tonestack - EQ or Equalizer. Where frequency can be attenuated or boosted. Most guitar amps use a passive tonestack, which will only allow for frequency attenuation.
- Bias - Setting idle current flow of a tube to be within the operating conditions of the amp. Can be either fixed-bias or cathode-bias.
- Fixed-bias - THIS IS NOT self-biasing. This is applying a small negative voltage to the grid of the power tube. This is a more efficient way of biasing than cathode biasing. In a fixed-bias setup, the cathode of the tube is grounded (0v).
- Cathode-bias - This is bringing the cathode to higher voltage potential than ground with a resistor and a capacitor. This is what is referred to as "Self-Biasing." This term is true to an extent. A cathode-biased amp can still have the bias adjusted, but may not have to.
