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 this amp's actual 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 bias and fixed bias sound different has almost nothing to do with the Class A vs Class AB label most amps carry incorrectly — the real mechanism is self-regulation and idle current headroom.
Choosing a Guitar Speaker by the Numbers
How to read a guitar speaker's actual specifications — sensitivity, power handling, resonant frequency — and why sensitivity matters more than most players think.
Output Transformers and Impedance Matching Explained
How a tube amp's output transformer matches high plate impedance to a low speaker impedance, why a mismatch or an open circuit is dangerous, and how solid-state minimum-load ratings differ.
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 stage by stage, 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 actually works, why Fender, Marshall and Vox sound so different from the same topology, and why turning Mid up turns it down.
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 both seem to disappear at low volume, why your 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 accurately using output transformer resistance and voltage drop — no shunt measurement, no oscilloscope, and it reads true plate current.
Taming the Blues Junior: A Blackface‑Flavored Makeover
Blues Junior mods with real component values: the 10k input grid stopper, the 100 pF volume treble bleed, the Twin tone stack swap, and the 1500 pF 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 turns into frequency response through your amp's output impedance, why reactive loads still don't feel like a real cab, and the IR double-counting 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 produces a fatter, higher-gain amp — with the gain staging, attenuators and feedback maths behind it.
