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.

Projects include:

Understanding the Long Tail Phase Inverter (LTPI) - This page has a detailed description of how the LTPI circuit works in guitar amplifiers.  It also shows a new method for balancing its outputs and a simulation of a Deluxe Reverb output stage with a fully balanced PI.    NEW

V-45 Head - A versatile 45w head with a high gain preamp and two OD stages.   NEW

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

BM lite project  - An evolving project log about designing a light-weight high-performance 5F6A chassis. 

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

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

Why valve amplifiers… what makes them unique and sound so good?

Princeton-AOT - a light-weight Princeton-size combo amp with 40w  NEW - 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

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

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

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

Spring Reverb - a simple and inexpensive spring reverb module

Waveform vs Spectrum - a simple experiment reveals some insights into how wave-shapes and harmonics are related

Disclaimer and safety precautions

Results of Uni mods done by other people and misc links

email for comments or questions: uneumann at gmail dot com

       Princeton-AOT -- 40 watts @ 24 pounds

last updates:
   lots more... I'm not bothering to track updates anymore
  4/28/16 - Waverform vs Spectrum
  3/31/16 - v3 of P-AOT
  2/6/16 - Flexi-Verb added to the Flexi-50 page
  1/21/16 - Flexi-50 page
  11/5/15 - GAO page
  10/21/15 - spring reverb page
  5/2/15 - BR4 version of the Bassman Redux
  1/30/15 - page for Princeton-AOT amp
  5/6/2014 - demo clips added for Bassman Redux
  3/8/2014 - page for Bassman Redux and revision for hum reduction
  4/28/2013 - page for Deluxe Plus amp
 10/15/2012 - demo clips for Uni ModD and new music tracks
  7/20/2012 - page on noise reduction for stratocasters
  5/20/2012 - page on noise reduction for single-coil pickups