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 · Tubes
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.
8 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.
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.
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.
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.
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.
