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GUITAR AMPS PAGE

SECTION 1: WELCOME

Welcome DIY vacuum tube amplifier constructors - this page is presented for your information and guidance.

It is intended to provide helpful hints to save you inevitable pain and suffering in your quest for audio and musical excellence, and to help you find joy in your chosen pathway to musical pleasure and fulfilment !!!!

Please note the information provided is not intended for the novice constructor. Basic circuit theory and construction techniques are not attempted herein because it is assumed you already know that and are competent in both.

My personal professional musical instrument playing and tube audio experience has been developed over more than sixty five years, so my contribution here is based upon a solid foundation of practical application of tube electronics to musical performance.

I was very fortunate to have lived through the golden age of tube guitar amps and rock and roll music - i.e. the fifties and sixties – during the early development of commercial guitar amps designed specifically for electric guitar in all of its forms.

Apart from the incorporation of discrete effects using solid state circuitry in many modern amps, those dedicated tube amplifier designs have stood the test of time to remain the preferred choice for today’s musicians.

In any event, you will soon see I am not a theorist, so whatever is say is based upon a combination of the reported experiences of others, helpful guidance from my electronic guru friends, reference to published texts from people who are considered to be reliable technical experts, electron tube manufacturers' manuals and data sheets, and my own experiments, research and experiences.

I hope it is of help to you in designing and constructing the very best electric guitar sound system for your needs.

THE GOAL

The purpose of this web page is to offer practical advice as to how the guitarist or DIY amplifier designer or builder can create a sound system that will enhance the musical talents and expression of the guitarist – be it yourself or someone else.

To do this the system needs to provide adequate power, adequate frequency response, low distortion, linearity (equal amplification over the useable frequency range), dynamic performance (responsiveness to light touch and asymmetrical peak signals) and ability to modify the tonal characteristics of the raw guitar to the desired sound.

Other important system attributes are choice of tubes and components, reliability, serviceability, layout, maintainability, size, weight and appearance etc.

The core philosophy is:

IT’S ALL ABOUT THE SOUND !!!!

SAFETY WARNINGS:

DO NOT attempt to design and/or construct a vacuum tube audio amplifier unless you suitably skilled, qualified and/or experienced.

The Author makes no claim whatsoever as to the validity or accuracy or otherwise of any statement, information or opinion contained in these pages and no liability will be accepted for any error or omission of any kind whatsoever.

Proceed only at your own risk!!

No warranty of any kind is expressed or implied as to the workability or performance of designs, concepts or equipment described herein.

Never forget Murphy's Law: IF SOMETHING CAN GO WRONG IT WILL !!!!

· VACUUM TUBES AND CIRCUIT COMPONENTS OPERATE AT HIGH VOLTAGES OF BOTH ALTERNATING CURRENT AND DIRECT CURRENT THAT CAN BE FATAL.

VACUUM TUBES OPERATE AT HIGH VOLTAGES – UP TO 1,000VDC - AND TEMPERATURES THAT CAN CAUSE PERMANENT INJURY, DYSFUNCTION OR DISABILITY - TO YOU OR SOMEONE ELSE.
DO NOT ATTEMPT TO CONSTRUCT, TEST, WORK ON, OR COME INTO PHYSICAL CONTACT WITH, LIVE ELECTRONIC EQUIPMENT UNLESS YOU ARE TRAINED OR OTHERWISE QUALIFIED TO DO SO.
NEVER REMOVE A PROTECTIVE COVER FROM ELECTRONIC EQUIPMENT UNLESS YOU ARE TRAINED OR OTHERWISE QUALIFIED TO DO SO, BECAUSE LETHAL MAINS AND HIGHER VOLTAGES ARE PRESENT INSIDE. ANY PERSONAL CONTACT THAT WILL CREATE A CIRCUIT IS SUFFICIENT FOR ELECTRICITY TO CONDUCT. DEATH IS PERMANENT.
Extra care should be taken with circuit designs using the B+ voltages listed in this guide.
Safety is of extreme importance not only to yourself the constructor, but also to other persons who may come into contact with your creation - particularly little children.
Live wiring should be fully insulated to prevent electrocution of yourself and/or users.
Tubes for use at B+ voltages over 450v DC require sockets made from materials that can withstand high voltages. Inferior materials may cause flashover or arcing, leading to burning, short-circuits and/or tube damage.
Many tube types require a top cap plate connection and such tubes must be carefully mounted to minimise wire length, proximity to other components and risk of accidental contact. Insulated caps are recommended. Do not solder directly to tube caps. Do not touch cap leads or terminals.

· Most vacuum tubes are glass encased devices that have been evacuated of air – i.e. they contain a vacuum atmosphere. If dropped or impacted they are likely to implode, shattering glass in any direction. Handle with care and respect. Do not drop or impact. Always pack and store in padded wrapping or the manufacturer's carton.

· When inserting into a tube into its socket always take care to align all the tube pins correctly with the matching socket. Incorrectly aligned tubes may result in high voltages being applied to low voltage circuit components or systems, and may result in short-circuit fault currents being applied with resultant expensive damage to tubes and equipment.

· DO NOT grasp a hot vacuum tube – particularly power tube and rectifiers

· To avoid serious and permanent tube damage when constructing an amplifier, always ensure the grid bias voltage is present at grids 1, 2 and 3 before applying B+ high voltages to the circuit. In this regard, cathode bias and back bias configurations are safer and more reliable designs than fixed bias.

· Unloaded electrolytic capacitors can hold their full charge for a week or more. Always ensure large HV electrolytic capacitors are fitted with suitable bleeder resistors to automatically discharge them after the amplifier is switched off - otherwise you may expose yourself to lethal current if you accidentally touch a live conductor. Persons familiar with assembling and servicing personal computers and suchlike - all of which feature fully insulated construction - must appreciate that tube amplifiers and ancillary equipment operate at high-voltages and, unlike computers, have unprotected open construction that is exposed to the touch - particularly components connected to the AC mains supply.

· Amplifiers that incorporate a “standby” switch still have full mains voltage and high voltages present in the system

· ALWAYS ensure your amplifier and guitar are grounded via the mains earth. Making contact with another amplifier or mains connected device that are separately grounded, such as microphone can result in electric shock.

Now that you have been suitably warned, let us proceed together to explore the world of vacuum tube audio.

WARNING - Exposure to extremely high noise levels may cause a permanent hearing loss.

Individuals vary considerably in susceptibility to noise-induced hearing loss, but nearly everyone will lose some hearing if exposed to sufficiently intense noise for a sufficient time.

Hearing loss or impairment may occur at a particular frequency or band of frequencies.

The U.S. Government’s Occupational and Health Administration (OSHA) has specified the following permissible noise level exposures:

Duration Per Day In Hours Sound Level dBA, Slow Response

90db - 8 hours max.
92db - 6 hours max
95db - 4 hours
97db - 3 hours
100db - 2 hours
102db - 1.5 hours max.
105db - 1 hour max.
110db - 30 minutes max.
115db - 15 minutes max.

According to OSHA USA, any exposure in excess of the above permissible limits could result in some hearing loss.

Your hearing health is in your hands.

Please note that no warranty is expressed or implied.

Intellectual property in the original applied engineering concepts expressed in this paper remains exclusively with their author Dennis R. Grimwood.

The whole or part thereof of this paper and/or the designs and design concepts expressed therein may be reproduced for personal use - but not for commercial gain or reward without the express written permission of the author and copyright owner.

REMEMBER - ALWAYS TAKE CARE WHEN WORKING WITH HIGH-VOLTAGE - DEATH IS PERMANENT!!

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This page last modified 12 July 2023

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