Blues Deluxe Mods: A Different Amp Than You Think
Real Fender Blues Deluxe schematic values for the tone stack, presence control and bias trim — and why its mod list differs from the Hot Rod Deluxe's.
Tech pages · Guitar Amps
The Bench, Written Down
Long-form write-ups of real repair and design work — measured, not guessed. Every article stands on its own; most come with the math and the schematic.
Searches titles, topics and the full text of every article.
15 articles
Cathode Bias vs Fixed Bias: What Actually Changes
Why cathode and fixed bias sound different has little to do with the Class A/AB label most amps wear incorrectly — the real mechanism is self-regulation.
Choosing a Guitar Speaker by the Numbers
How to read a guitar speaker's real specs — sensitivity, power handling, resonant frequency — and why sensitivity matters more than most players think.
Output Transformers and Impedance Matching Explained
How an output transformer matches high plate impedance to a low speaker load, why a mismatch or open circuit is dangerous, and what 'minimum load' protects.
Reading an Amp Schematic
How to read a tube amp schematic from scratch: the symbols that cover almost every circuit, how to trace a signal path, and where the four supply nodes are.
The Five Faults Behind Most Amp Repairs
The five most common tube-amp faults from the actual repair bench, what each one sounds like before it fully fails, and roughly how to tell them apart.
What a Tone Stack Actually Does
How the passive Bass/Mid/Treble network in a guitar amp works, why Fender, Marshall and Vox sound so different from the same topology — and why Mid inverts.
What the Presence Knob Really Does
How amplifier negative feedback and the presence control actually work, with schematic-verified feedback amounts for Fender, Marshall and Bassman-family amps.
Why Everything Sounds Better Louder
Equal-loudness contours explain why bass and treble fade at low volume, why EQ choices don't survive a volume change, and how to set tone controls honestly.
How to Bias a Fixed‑Bias Push‑Pull Tube Power Amp
Bias a fixed-bias push-pull tube amp using output-transformer resistance and voltage drop — no shunt measurement, no oscilloscope, true plate current.
Taming the Blues Junior: A Blackface‑Flavored Makeover
Blues Junior mods with real component values: the input grid stopper, the treble-bleed cap, the Twin tone stack swap, and the cap that makes it nasal.
How to Measure Guitar Amplifier Output Power?
How amplifier power is really measured, why a cranked 100 W amp delivers close to 200 W, and why speaker sensitivity — not watts — decides which amp is louder.
Why Reactive Loads Sound Different From Real Cabinets
How speaker impedance becomes frequency response through amp output impedance, why reactive loads don't feel like a cab, and the IR double-count trap.
The Ultimate Hot Rod Deluxe Mod
Fix the Hot Rod Deluxe's PCB-cooking dropping resistors, then rework the power amp and preamp for a blackface-style feel and usable drive channels.
Plexi Marshall Heresy: "The Grinder" Mod
How replacing a Marshall's cathode follower with a fourth gain stage makes a fatter, higher-gain amp — with the gain-staging and feedback maths behind it.
