A DESKTOP REFERENCE OF HIP VINTAGE GUITAR AMPS, Gerald WEBER.

A DESKTOP REFERENCE OF HIP VINTAGE GUITAR AMPS, Gerald Weber.

A Desktop Reference of Hip Vintage Guitar Amps
Series: Book
Publisher: Kendrick Books
Format: Softcover
Author: Gerald Weber

If you have questions about guitar amplifiers-how to fix them, how to restore them, or how to hot-rod them-this book has the answer. This book is written for the guitarist or collector who desires a common sense approach to understanding the essence of vintage tube amps and vintage tube tone. Not written for engineers, it does not contain engineering formulas, polar mathematic equations, or abbreviations that are assumed you should know. Gerald Weber, a regular columnist for Vintage Guitar magazine, shares the knowledge he has accumulated over the years of repairing and building his line of Kendrick amps.
Inventory #HL 00330225
ISBN: 9780964106000
UPC: 073999302257
Width: 6.0"
Length: 9.0"
512 pages

Gerald Weber has written many articles on tube guitar amplifiers for Vintage Guitar magazine, and this book is a compilation of those articles, plus excerpts from his "Ask Gerald" question and answer column. Written for the guitarist or collector who wants a common sense approach to understanding the essence of vintage tube amps and vintage tube tone, this essential guide will answer questions on how to fix, restore, or hot-rod vintage amps. Includes easy-to-follow text, a complete glossary of terms, many photos and detailed schematics, and a listing of dealers and sources.

If you have questions about guitar amplifiers-how to fix them, how to restore them, or how to hot-rod them-this book has the answer. This book is written for the guitarist or collector who desires a common sense approach to understanding the essence of vintage tube amps and vintage tube tone. Not written for engineers, it does not contain engineering formulas, polar mathematic equations, or abbreviations that are assumed you should know. Gerald Weber, a regular columnist for Vintage Guitar magazine, shares the knowledge he has accumulated over the years of repairing and building his line of Kendrick amps.

If you want to know about vacuum tube guitar amplifiers & what affects tone, this book bypasses the confusion & gets down to the essences of guitar amplifiers. Written for the guitarist or collector, this book is a common sense approach to understanding vintage vacuum tube guitar amplifiers. Not written for engineers, it does not contain engineering formulas, polar mathematic equations, or abbreviations that are assumed you know. When a new term is used for the first time, a definition of that term appears at the end of the chapter in a mini-glossary. The Author is president & owner of Kendrick Amplifiers, who manufacture vacuum tube guitar amplifiers & operate the largest vintage amp restoration shop in the country. He writes question-&-answer columns for "Vintage Guitar Magazine." Many of the articles are reprinted in this book. Over 200 schematics & layout diagrams, dozens of modifications, a whole section of tips & tricks, circuit comparisons & pictures. A must for anyone interested in tube guitar amps.

 

 

Gerald Weber wrote his first monthly column for Vintage Guitar magazine over three years ago. It was the first technical, article that we had' ever printed and Gerald's writing soon became a very popular part of the magazine. Since that time, his articles have generated more reader mail than any other regular feature of the magazine. The letter writers almost always express their appreciation for Gerald freely sharing his vast knowledge of guitar amplifiers and how to "tweak" them for better performance. Whether the readers use this information to work on the amps themselves, or just to be able to deal with repair people, Gerald's words make for a better informed-and happier-guitar player. In the pages of this book, Gerald continues to freely share this information-knowledge that he has accumulated over the years repairing and building guitar amps. His line of Kendrick amplifiers and related components come with the highest references and he is always striving for quality and that "Killer Tone." So, if you have questions about guitar amplifiers- how to fix them, how to restore _ them, or how to hot-rod them-look inside,

Gerald Weber has the answer! Alan Greenwood Publisher

Vintage Guitar Magazine

 

 

PREFACE

When I began writing articles for Vintage Guitar Magazine several years ago, my original intention was to share my knowledge with those who care as much about tube guitar amps as I do. At the time, I had no idea that this book would eventually write itself. This book is actually a compilation of those articles and a compilation of the" Ask Gerald" question and answer column with the addition of some schematics and a reprint of the "Trainwreck Pages" and some other reprints. This book is written for the guitarist or collector who desires a common sense approach to understanding the essence of vintage tube amps and vintage tube tone. Not written for engineers, it does not contain engineering formulas, polar mathematic equations, or abbreviations that are assumed you should know. In fact, when a term is used for the first time, a definition of that term will appear at the end of the chapter in a mini-glossary. When you come across a word that is unfamiliar, you should look at the mini-glossary at the end of the chapter and clarify the word before proceeding. This will keep everything clear for you. DISCLAIMER: Tube amplifiers contain potentially lethal high voltages even after they are unplugged, that may cause personal injury or death. Do not attempt to repair or modify any amplifier unless you are absolutely certain that you know what you are doing.

 

Schematic. One of these losses occurs in the audio transformer. In times of old, virtually all transformers were wound directly on a laminated core with only paper insulating the windings from the core; modern transformers are wound on plastic or nylon bobbins, much thicker than paper, resulting in greater loss and consequently less fidelity. Try this: hook up your guitar and play it and listen to how it sounds. ow take a small screwdriver and adjust the pickups so they are a quarter of an inch further away from the strings. Now how does it sound? From this experiment, you can see for yourself that the further a magnetic source your guitar strings) is away from an inductive coil (your pickups), the less efficient the signal transfer. This is exactly the same phenomenon occurring in a plastic bobbin transformer. The extra distance of a plastic bobbin kills tone that would have been captured by the closer, paper-insulated vintage style transformers. Also many vintage transformers were interleaved, a practice not common in modern amps. Any audio transformer generally has two coils wound on the same core. Interleaving means winding a little bit of the first winding, then a little bit of the second winding, then a little of the first, then a little of the second, etc., until both windings have the correct number of turns. Modern transformers are usually wound by winding all the turns of one winding, and then all the turns of the other winding. Obviously the interleaved transformer will sound better because it is more efficient and better at producing low end, with richer harmonics. In the 50s and 60s, coupling capacitors were typically made by placing two small sheets of paper (called the dielectric) between two small pieces of foil. A lead was attached to each piece of foil, and the paper and foil sandwich (double decker) was rolled up like a cigarette. Often, the finished cap was encased in plastic, wax, or epoxy. These caps had a very rich sound with nice low end. Nowadays however, technology and automation have taken us to a new level in capacitor manufacture. Polystyrene, mylar, polyester, and anything but paper are commonly used as the dielectric but do not have the same sound as paper dielectrics. Although audiophiles will tell you that polystyrene caps have the best sound (and maybe they do for stereo systems), I prefer the polyester tubular foil capacitors as the ones sounding the most like vintage for guitar amps. These caps are the Mallory 150 series caps and are made by spraying ...

 

Amps of Our Times - Vintage vs. Modern

 

... conductors of a capacitor. Paper, air, electrolyte, mica, mylar, polyester, and ceramic are some of the dielectrics that are used.

DISTORTION-noun- The difference between what goes into an electronic device and what comes out.

DYNAMICS-noun-The loud/soft quality of music that gives it character.

ENVELOPE-noun-The changing dynamics of a vacuum tube circuit that can be heard as an attack, decay and sustain volume level when a note or a chord is played through the amp.

E.Q.-noun-Abbreviation for "equalizer."

FIXED-BIAS-adjeetive-A way to achieve bias in a vacuum tube in which a fixed amount of negative voltage is placed on the grid of a tube. This is almost always done on output tubes and almost never done on preamp tubes.

GAIN-noun-The amount of voltage amplification in the preamp section of an amplifier. This voltage amplification ultimately drives the power tubes which do not add any more gain. The power tubes add current (power).

GRID-noun-One of the internal parts of a vacuum tube. This is usually where

the input signal connects.

HARMONICS-noun-The frequencies that are related to the fundamental frequency by being multiples of the fundamental frequency.

HEADROOM-noun-The volume level that is attainable before clipping occurs.

IMPEDANCE-noun-Sum of all resistance, capacitive reactance, and inductive reactance.

INTERLEAVED-adjeetive-A way of winding a transformer in which a little bit of the primary is wound, then a little of the secondary is wound, then a little primary, then a little secondary, etc. until the transformer is wound. The more interleaves, the better the efficiency.

PHASE INVERTER-noun-The circuit in a push pull amplifier that feeds the power tubes signal. It feeds one power tube an in phase signal and the other power tube an out of phase signal. The tube for this circuit is always located next to the power tubes.

PICOFARAD-noun-A very small amount of capacitance that is equal to a trillionth of a farad (.000,000,000,00 I farads). Sometimes also called "micro micro

farads."

PLATE-noun- The part of a vacuum tube that has high voltage on it. Except in a cathode follower circuit, the output is always taken from this part of the tube.

PLATE VOL TAGE-noun- The voltage that is applied to the plate of a vacuum tube. Higher voltages give more headroom and high end, lower voltages give more breakup and a browner tone. All tweed amps had relatively lower plate voltages.

PREAMP-noun-The section of an amplifier whose function is to add gain. Preamps are always before the output stage.

RECTIFIER TUBE-noun-A vacuum tube with no grid, whose purpose is to change alternating current to direct current. Current flows from the cathode to whichever of the two plates that happens to be positive at the time.

 

... relatively lower impedance cathode follower circuit. This circuit increases odd order harmonics thus giving a crunchy tone. This is the same crunch that you hear in all early Marshalls. Originally, this circuit was used so that the tone controls would not load down the signal. Later blackface Fenders did not use this circuit and that is why blackface amps will have no volume if all the tone controls are turned to the lowest setting. (The signal is loaded down to the point that nothing is left to amplify.) Shortly after the 5E6 came out, Fender changed the design slightly to a 5E6A. This amp was identical to the 5E6 except that the bias voltage was increased somewhat. (They were probably having problems with power tubes blowing and increasing the bias would have the tubes run cooler.) Also the tone cap values were slightly different on the 5E6A. In 1958, the 5F6 became the next evolution of the 4X10 Bassman. Sometimes referred to as a four hole Bassman (it had two inputs for bright and two inputs for normal-each channel having a high and low gain input), this model had quite a few design changes, although cosmetically it looks like they simply added two inputs and a middle control. There is much more to it than that. For instance, the negative feedback across the second stage was removed, thus increasing gain. Although the 12AY7 was still used on the first gain stage, the second tube was changed to a 12AX7 increasing gain even further. The tone control design was changed to what would become a classic design later used by Marshall, Vox, and many others. A cathodyne style phase inverter was dropped in favor of the familiar long-tail pair style phase inverter that has remained a characteristic of virtually all Fender tube amps to date. The choke was moved between the screens and center tap of the audio transformer-a place it has been ever since in all Fender amps. 100 ohm screen grid resistors were added and the output tubes were changed to the higher fidelity 5881s. The wattage increased to about 40 watts because the plate voltage was increased from 405 volts on the 5E6A to 427 volts on the 5F6 and the preamp gain was increased considerably. 5881 power tubes are different from the 6L6Gs in several ways. First the 5881 has always been considered a high fidelity version of the 6L6G which is considered an industrial public address tube. 5881s are rated at 23 watts per tube compared to the 6L6G's 19 watts. Being a ... Kendricks

 

HIP VINTAGE AMPS

Amps of Our Times-Vintage vs. Modern

The Tweed Champ

The Tweed Deluxe

The Definitive 4X10 Bassman

The Deluxe Reverb

The Super Reverb

The Vibroverb

 

TIPS AND TRICKS

A Tube is a Tube, Right?

The Simple Truth About Biasing Your Amp

Unwinding the Transformer Puzzle

Important Facts About Jensen Speakers

How to Make Your Amp Sound Right

Easy Tricks to Juice Your Vintage Amp

Ten Easy Mods for Your Super Reverb

Ten Easy Mods for Your Pro Reverb

Juice Up That 6G15 Fender Reverb

Resurrecting That Tube Echoplex

Silver to Blackface Conversion for Twin Reverb

 

THE TRAINWRECK PAGES-By KEN FISCHER

 

QUESTIONS AND ANSWERS

 

SCHEMATICS

Ampeg

Fender

Gibson

Hiwatt

Magnatone

Marshall

Rickenbacker

Silvertone

Vox

 

REVIEWS OF KENDRICK PRODUCTS

Gerald Weber, the Tweed King

 

CATALOG OF KENDRICK PRODUCTS

 

 

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