Welcome to


This is a site mostly about valve (vacuum tube) amplifiers for guitar and the never ending search for tone and reducing hum and noise. While somewhat technical, it should be readable by most people who have had exposure to circuits and amplifiers in general.

Design Books:

Guitar Amplifier Design: Tubes and Semiconductors Play Together - A new book about designing a novel 100 watt guitar amp and amps in general. Updated with SoloVerb3 reverb card.

Guitar Amplifier Overdrive - A visual explanation of over-driven tube circuit behaviors and "evolution of an OD stage"

Pickup Hum Cancelling:

Noise reduction for single-coil pickups - with Telecaster and G&L S-500 sound clips

Amp Circuits and Mods:

Tuning DCCF Harmonics - An introduction to the operation and tone quality created by the ubiquitous Direct-Coupled Cathode Follower circuit.

Understanding the Long Tail Phase Inverter (LTPI) - A summary of how the LTPI circuit works in guitar amplifiers.

Waveforms and Spectra - Examine the relationships between common waveshapes and their harmonic content.

Modify a classic (THD Univalve) - improve its tonal range and put this amp in a class of its own (with ModD demo clips)

Amp-Aid for Vintage Tube Amplifiers - Bias tremolo and reverb/FX/bias additions for the 5F6a Tweed Bassman. Analog spring reverb for the 5e3 Tweed Deluxe with sample clips.

Flexi-50 fix and Flexi-Verb - fixes for two nagging problems with the THD Flexi-50 and a dedicated spring reverb FX unit tailored specifically to the Flexi FX loop.

Modify a low-cost valve amp (Epiphone Valve Junior) to sound great and deliver a wide tonal range

Spring Reverb - a simple and inexpensive spring reverb module

360 V DC Converter - a small simple power source for tube circuits

Novel Amp Projects:

V-45 Head - A versatile 45w head with a high gain preamp and four-triode OD stage. NEW version v1.5 based on GAD book design principles.

Teluxe 25 - A full feature 25w amp in a Tweed Deluxe cab/chassis.

BM lite project - An evolving project about a light-weight high-performance 5F6A chassis. New dual-channel 100w BML4 design.

Princeton-AOT - a light-weight Princeton-size combo amp with 40w - the Sugar Bee amp based on this AOT design is featured as "Editors' Pick" in Guitar Player magazine and "VG Approved" by Vintage Guitar magazine (see pics below).

Deluxe Plus - a cascode preamp in a classic AB763 Deluxe Reverb Amp. Version 2 and the search for 5e3 tone

Building a Bassman clone from a Weber 5F6a kit - build guidance, lessons learned, and features you may want to add

Bassman Redux - a new variation on the 5F6a Tweed Bassman, adding a blend-able Grit channel and a Master Volume - now describing a fourth version of this project

Less Bass Bassman - remove the boominess from a Bassman with a switch for three tone stack options


Univalve mods done by other people and misc links to music electronics sites

My Music - some guitar recordings from many years ago.

email for comments or questions: uneumann at gmail dot com


Princeton-AOT -- 40 watts @ 24 pounds



BML4 100w

Teluxe 25

BM Lite


Deluxe Plus

Bassman Redux

Univalve w/mods

Valve Jr w/mods