A

Action. String height above the frets, usually measured at the 12th fret — set by saddle height after neck relief and nut height are already correct, since both of those change what 'correct' action means. Bridges, Nuts, Frets, and Setup →

Alnico. A family of magnet alloys (aluminum-nickel-cobalt) used in most vintage-style pickups — the specific alnico grade (2 through 5) trades output and brightness against compression and softness. Pickup Theory and Types →

Aliasing. A digital system misrepresenting a frequency above half its sample rate as a different, lower, often dissonant frequency — the digital equivalent of a wheel appearing to spin backward on video. DSP Basics for Guitarists →

Anode. An LED's positive leg — the longer of the two, and the one that must connect toward the positive supply for the LED to conduct and light up. LED Indicator Wiring →

Asymmetric clipping. Clipping the positive and negative halves of a waveform differently (mismatched diode types or an unbalanced pair), producing more even-order harmonics and a warmer, more "tube-like" character. Transistors and Diodes →

B

B+. The high-voltage DC supply rail in a tube amplifier, typically 300-500V — the rail every filter capacitor in the power supply chain is charging, and the reason those capacitors stay dangerous long after the amp is unplugged. Rectification and Power Supply →

BBD (bucket-brigade device). A chain of capacitor "buckets" that passes a sampled voltage from one to the next, clocked in sequence — analog the whole way through, never converted to a number. The mechanism behind true analog delay and most vintage chorus/flanger circuits. Delay →

Bias point. The DC resting voltage a transistor's or op-amp's terminals sit at with no signal present, predicted from a schematic's resistor values using Ohm's Law — the first thing checked when debugging a stage that isn't working. Ohm's Law and Basic Circuit Theory →

Bias (tube). The idle current an output tube draws with no signal present, set by the grid-to-cathode voltage — drifts with tube wear and has to be reset whenever output tubes are replaced, since it's also what keeps the output transformer's core from saturating. Common Amp Mods →

Bit depth. How precisely each individual digital sample is measured — 16-bit represents 65,536 distinct levels, 24-bit over 16 million. Too low a bit depth introduces quantization noise, not pitch or timing error. DSP Basics for Guitarists →

Buffer (impedance). A circuit that presents a high input impedance to the guitar and a low output impedance to everything downstream, at unity gain — it protects tone from cable capacitance and a long pedal chain without amplifying anything. Boost and Buffer →

Buffer (DSP). A fixed-size block of audio samples handed to code all at once by the audio callback, rather than one sample at a time — smaller buffers mean lower latency but less processing time per block. DSP Basics for Guitarists →

Buffered bypass. Footswitch wiring that keeps a unity-gain buffer stage in the signal path at all times, even with the main effect switched off — trades "the pedal never touches your tone when off" for better long-cable tone preservation. Footswitch and True-Bypass Wiring →

C

Cathode. An LED's negative leg — the shorter of the two, often marked with a flat edge on the LED's body. LED Indicator Wiring →

Cathode bypass capacitor. A capacitor across a tube (or transistor) stage's cathode resistor that removes that resistor's negative feedback at audio frequencies, increasing the stage's gain — pulling it out entirely is a deliberate way to trade gain for a stage's specific clipping character. Common Amp Mods →

Chorus. A short (~5-25ms), LFO-modulated delay line blended with the dry signal — the pitch-wavering copies layered underneath create a thickening, "more than one player" effect. Modulation →

Class A / Class AB. How much of a signal cycle a push-pull output stage's tubes conduct through — Class A keeps both tubes conducting at all times (low efficiency, low crossover distortion); Class AB conducts less than the full cycle (higher efficiency and power, some crossover distortion at low levels). Power Amps and Transformers →

Clipping. Flattening a signal's peaks once it exceeds a threshold — the mechanism behind every fuzz, overdrive, and distortion circuit, produced either by an overdriven transistor stage or by diodes conducting past their forward voltage. Transistors and Diodes →

Coil-split. Shorting one coil of a 4-conductor humbucker to ground (and breaking the series link between the coils) to leave the other coil running alone — thinner, brighter, and noisier than the full humbucker, closer to a single-coil. Switching Systems →

Current-limiting resistor. The resistor placed in series with an LED to keep its current within a safe range — without one, an LED's near-zero resistance lets it pull far more current than it's rated for. LED Indicator Wiring →

D

Daisy chain (power). A single power supply split into multiple output taps so one brick powers an entire pedalboard — only works within the supply's total current budget, shared across every pedal plugged into it. Daisy-Chaining Multiple Pedals →

Damping factor. The ratio of speaker impedance to amplifier output impedance — high damping factor (solid-state, direct-coupled) tightly controls the speaker cone for a tighter bass response; low damping factor (tube, via an output transformer) lets the cone move more freely for a looser, 'warmer' low end. Solid-State and Hybrid Amps →

Depth (modulation). How far an LFO swings the parameter it's modulating on each cycle — alongside rate, one of the two core controls shared by every modulation effect. Modulation →

Diode. A one-way valve for current: it conducts freely in one direction and blocks the other almost entirely. The basis of every clipping stage in a pedal. Transistors and Diodes →

F

Feedback (delay/reverb). How much of a delayed signal gets routed back into the circuit's own input, determining how many audible repeats occur before they decay — pushed high enough, feedback reaches or exceeds unity gain and the repeats self-oscillate instead of decaying. Delay →

Feedback loop (op-amp). The path routing a fraction of an op-amp's output back to its input, which is what tames its raw open-loop gain into a precise, controllable amplifier. Op-Amps →

Flanger. The same short modulated delay line used for chorus, with a feedback path added around it — produces a sweeping comb-filter "jet plane" notch effect. Modulation →

Forward voltage (Vf). The roughly fixed voltage drop across an LED (or any diode) once it's conducting — around 1.8-2.2V for a standard red LED — below which it barely conducts at all. The starting point for calculating a current-limiting resistor. LED Indicator Wiring →

G

Germanium. An older transistor/diode material with a lower turn-on voltage and softer, more gradual clipping than silicon — associated with vintage fuzz tone, and temperature-sensitive in a way silicon largely isn't. Transistors and Diodes →

Ground loop. Multiple physical paths between points that should sit at the same ground potential — tiny resistance differences between those paths produce a voltage difference that shows up as audible 60Hz (or 50Hz) hum. Enclosure Prep and Grounding →

H

Half-split method. The fastest way to localize a fault in any circuit: probe the midpoint of the signal path first rather than checking components in order, then repeat inside whichever half turns out to be faulty — narrows any circuit down to the failing stage in a handful of measurements. Systematic Troubleshooting →

hFE. A transistor's gain — the ratio between the larger current flowing collector-to-emitter and the small current controlling it at the base. The spec quoted when one transistor is described as "having more gain" than another. Transistors and Diodes →

Humbucker. Two coils, wound in opposite directions with opposite magnetic polarity, connected in series — the opposite windings cancel mains hum while the string signal from both coils adds together, at the cost of roughly double a single-coil's inductance (and darker tone). Pickup Theory and Types →

I

Intonation. Adjusting saddle position so a string's fretted 12th-fret note matches its 12th-fret harmonic, compensating for the string stiffness that makes a fretted note read slightly sharp of the ideal — a per-string, one-point compensation, not a perfect-everywhere fix. Necks, Scale Length, and Intonation →

Inverting amplifier. The standard op-amp gain-stage arrangement in pedal circuits: input feeds the op-amp's inverting (−) input through a resistor, and a feedback resistor sets the gain as −(feedback resistor ÷ input resistor). Op-Amps →

Isolated power supply. A multi-output power supply where each output has its own separate transformer winding or DC-DC converter, so pedals on different taps share no internal ground path — eliminates the ground-loop risk a shared, non-isolated supply carries. Daisy-Chaining Multiple Pedals →

L

LFO (low-frequency oscillator). An oscillator too slow to hear directly (typically well under 20Hz) that outputs a smoothly rising-and-falling control voltage instead of an audible tone — the shared mechanism behind chorus, flanger, phaser, tremolo, and vibrato, each steering the LFO at a different target. Modulation →

M

Motorboating. A slow, rhythmic 'putt-putt' oscillation caused by a power supply unable to hold its rail steady under the circuit's own current demands — a power-supply stability fault, not a signal-path oscillation, and rarely fixed by anything in the gain stages themselves. Amp Troubleshooting →

N

Non-inverting amplifier. An op-amp gain stage with its feedback ratio set to exactly 1 (a buffer) or above 1 (a boost) — the topology behind the simplest gain circuits in a pedal. Boost and Buffer →

Nyquist theorem. The rule that a sampling rate can only accurately capture frequencies up to half of itself — at 48,000Hz, frequencies up to 24,000Hz are faithfully represented; anything above that aliases. DSP Basics for Guitarists →

O

Op-amp. A small integrated circuit that compares two input voltages and outputs a massively amplified version of their difference — tamed by a feedback resistor into a precise, controllable gain stage. The workhorse behind most overdrive and distortion circuits. Op-Amps →

Open-loop gain. An op-amp's raw, untamed gain with no feedback resistor applied — often 100,000× or more, so extreme that any tiny input difference slams the output to one extreme or the other. Op-Amps →

P

Phaser. A sweeping notch effect built from a chain of LFO-swept all-pass filter stages, with no delay line involved at all — the one modulation effect in that family that isn't built from a modulated delay. Modulation →

Piezo pickup. A pickup that senses string or body pressure through a piezoelectric element rather than magnetic flux — brighter, more percussive, and an extremely high (multi-megohm) source impedance that requires a dedicated preamp to use at all. Piezo and Hybrid Systems →

Pickup. The transducer that converts string vibration into an electrical signal — electrically a resonant RLC circuit whose inductance, self-capacitance, and downstream loading (pot value, cable length) together set the resonant peak that defines its tone. Pickup Theory and Types →

Polarized. A component (electrolytic/tantalum capacitors, LEDs, diodes) that only works correctly installed in one direction — reversing it can fail to work, or in an electrolytic capacitor's case, heat, bulge, or vent. Resistors and Capacitors →

Potentiometer (pot). A resistor with a movable contact (the wiper) — the part behind every knob on a pedal, turning a fixed total resistance into an adjustable one as the wiper slides. Potentiometers →

Q

Quantization noise. The audible noise floor introduced by a digital sample's limited bit depth — more apparent at low signal levels, functionally similar to (but mechanically different from) analog hiss. DSP Basics for Guitarists →

R

Rectifier (tube vs. solid-state). The component converting an amp's AC mains into DC. A tube rectifier has real internal resistance, so B+ sags under heavy playing — a solid-state rectifier's near-zero resistance keeps B+ stiff instead, a genuine and audible tonal tradeoff, not just an efficiency difference. Rectification and Power Supply →

Red-plating. An output tube drawing so much current its plate glows visibly orange-red — a sign of a serious bias fault requiring an immediate power-down, not a cosmetic curiosity. Amp Troubleshooting →

Reference designator. A schematic's letter-plus-number label tying a drawn component to its row in the parts list — R for resistor, C for capacitor, Q for transistor, D for diode, U/IC for integrated circuits, VR/P for potentiometer. Reading Schematics →

Reverse-polarity protection. A diode placed in series with an incoming power line, oriented to conduct normal-polarity current through with a small voltage drop but block current entirely if the supply is wired backwards. Power Supply Conventions and Polarity Safety →

Resonant peak. The frequency where a pickup's inductance and capacitance form a resonant circuit and its output is highest — the single biggest factor separating a bright single-coil's voicing from a darker humbucker's, more predictive of tone than DC resistance. Pickup Theory and Types →

Ring. A TRS jack's third contact (beyond tip and sleeve) — in pedal wiring, repurposed to carry a battery's negative return through a switching jack rather than a second audio channel. Jack Wiring →

RWRP (reverse-wind, reverse-polarity). A pair of single-coil pickups wound in opposite directions with opposite magnetic polarity, so mains hum picked up by both cancels when combined while the string signal — which differs by position along the string — adds constructively. Pickup Theory and Types →

S

Sag. A tube rectifier's B+ voltage momentarily dropping under heavy current draw — the mechanism behind the touch-sensitive compression players describe as an amp's 'feel,' absent in solid-state-rectified designs. Rectification and Power Supply →

Sample rate. How many times per second a continuous signal is measured and converted into a number — 44,100Hz and 48,000Hz are the common standards, chosen to sit comfortably above twice the upper limit of human hearing. DSP Basics for Guitarists →

Scale length. The distance from nut to bridge saddle, set as twice the nut-to-12th-fret distance — determines both string tension for a given gauge and exactly where every fret has to sit, which is why a neck can't be swapped onto a body with a different scale length without moving the bridge. Necks, Scale Length, and Intonation →

Self-oscillation. A delay's feedback control pushed to or past unity gain, so repeats stop decaying and instead sustain indefinitely or build in volume — a deliberate, commonly-used technique, not a malfunction. Delay →

Slew rate. How quickly an op-amp's output can change in response to a change at its input — the ProCo Rat's unusually slow-slew-rate LM308 rolls off high frequencies and is a deliberate part of its dark, compressed clipping character. Overdrive and Distortion →

Star ground. Wiring every ground connection in a circuit as a direct, separate wire back to one single physical point, rather than daisy-chaining grounds from part to part — the wiring topology that avoids ground loops. Enclosure Prep and Grounding →

Switching jack. A TRS jack whose ring and sleeve contacts are physically bridged together only when a standard mono plug is inserted — the mechanism behind the battery-cutoff trick. Jack Wiring →

T

Taper. How a potentiometer's resistance changes across its rotation — linear ("B") changes at a constant rate, audio/logarithmic ("A") changes slowly at first then rapidly, matching how human hearing perceives loudness. Potentiometers →

Tone stack. The passive resistor-capacitor filtering stage placed after a gain/clipping stage, shaping which frequencies dominate once clipping has already happened. Overdrive and Distortion →

Treble bleed. A small capacitor, often paired with a resistor, wired across a volume pot's input and wiper lugs to give high frequencies a path around the low-pass filter the pot otherwise forms with the pickup — keeps a guitar from going dark as the volume rolls down. Pots, Caps, and Tone Controls →

Tremolo. An LFO modulating signal amplitude (volume) — the simplest of the five modulation effects, with no delay line involved. Historically mislabeled on vintage Fender gear, where "vibrato" and "tremolo" were swapped. Modulation →

TRS / TS jack. TS (mono) has two contacts — tip and sleeve. TRS (stereo) adds a third, ring. Pedal input jacks are almost always TRS, not for stereo audio, but for the ring-contact battery-cutoff trick. Jack Wiring →

True bypass. Footswitch wiring where, in the "off" position, input jack connects directly to output jack through a mechanical contact — the guitar signal never reaches the circuit board at all. Footswitch and True-Bypass Wiring →

Tube (valve). The active amplifying device in a tube amp — a small grid voltage controlling a much larger plate current, the same small-signal-controls-large-signal mechanism as a transistor, but clipping gradually with even-order-dominant harmonics instead of a transistor's harsher, odd-order-dominant clipping. Tube Amp Fundamentals →

Truss rod. A steel rod (or dual rods) embedded in the neck that counteracts string tension — adjusting it changes neck relief, and it's always the first step in a full setup because relief changes what every later measurement means. Necks, Scale Length, and Intonation →

V

Vibrato. An LFO modulating pitch via a short, 100%-wet modulated delay line, with no dry signal blended in. Historically mislabeled on vintage Fender gear as "tremolo arm" for the whammy bar, despite modulating pitch, not amplitude. Modulation →

W

Wetting. The way molten solder flows onto and bonds with a heated component lead and pad — a properly wetted joint looks shiny and cone-shaped; a joint that never wets looks dull, grainy, or ball-shaped and often isn't actually connected. Soldering and Tools →