Vacuum Tube Amplifiers

Same old technology, same great sound

Vacuum Tube Amplifiers

Same old technology
same great sound

This is the official site of EJ Jurich author of Vacuum Tube Amplifier Basics. Written for hobbyist interested in building high-fidelity vacuum tube audio systems, the book is concise with illustrations and examples.

Vacuum Tube Amplifier Basics

Vacuum Tube Amplifier Basics
EJ Jurich

There is a growing number of audio enthusiasts and hobbyist interested in creating their own vacuum tube amplifiers. If one has the necessary technical information, high quality tube amplifiers can be assembled using point-to-point hand wiring.

For the novice not versed in electronics several sections of the book cover electronic basics. Includes how capacitors work, voltage, current, ohms law, reading circuit drawings plus other related information.

Principles of vacuum tube operation includes function of grids, effect of tube capacitance, tube resistance, heat dissipation and voltage gain. A table of component values for the popular 12AX7 in various operating parameters simplifies pre-amplifier stage design. Power supply sections cover vacuum tube and solid state rectifier conversion of AC to DC and DC filtering. A sample power supply is used to explain calculating loads, determining required transformer ratings and component values. Includes high voltage, bias and filament supplies.
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A Brief Bio of EJ Jurich
EJ Jurich

Born May, 1945
Originally From Chicago

Radio Broadcast Engineer, retired

In 1955 started tinkering with vacuum tube electronics at the age of ten. My father worked for Western Electric and was well versed in electronics. As I experimented with circuits I would consult my father. Between 1955 and into the mid 1970s built several kits both Knight and Heath Kits. In 1969 passed exams obtaining an FCC First Class License, then started a career in radio broadcast engineering.
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The Allure of Vacuum Tube Amplifiers

There are a few possible reason for the allure of vacuum tube amplifiers. Perhaps it is nostalgic, status symbol of owning a vacuum tube amplifier or possibly because of the way audio sounds amplified through vacuum tubes. If you ask audio enthusiasts who prefer vacuum tube amplifiers, more than likely they will say it's the sound. The opinion of a few audio enthusiasts may not mean much. How about the opinion of a few thousand ordinary people.
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Vacuum Tube Gain Controlled Amplifier

Vacuum tube audio processor for maintaining an average level while preserving dynamics using an all triode vacuum tube design built around the 12AX7 dual triode. This is the gain controlled amplifier mentioned in The Allure of Vacuum Tube Amplifiers.

A gain controlled amplifier (also called a compressor) is an amplifier that maintains an average output level over a larger input level range. This type of amplifier is used to prevent over-driving audio systems and keep levels in a more comfortable listening range.
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6SN7 Headphone Amplifier

6SN7 headphone amplifier

This is an experimental headphone amplifier using one section of a 6SN7 as the output tube. Power output at 1KHZ is ½ watt sufficient to drive headphones loud and speakers in a small room to a moderate listening level. With the tone control set in middle rotation frequency response measured 40HZ to 18KHZ -3db points.
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Amplifier Power
Sound Pressure Levels

Building a vacuum tube amplifier can be expensive, transformers and power output tubes can be especially pricey. If you are working with a tight budget, there are options available to help reduce costs. Backing off on amplifier power and referring to sound pressure levels for loudness can save you money and save your hearing.
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Importance of Filament Voltage

Tubes have an optimal filament voltage, for example 6.3 volts, 12.6 volts, etc. Although a voltage range above and below the optimal voltage is specified in datasheets there is good reason to not apply more than the optimal value.
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Design Calculators

The following are online calculators that can be used for amplifier design approximations. Some of the calculators require Javascript enabled. The calculators are located off-site and open in a new window. After a circuit is built it is best to take measurements and verify circuit operation.

Power Transformer Current Calculator

Triode Voltage Amplifier Calculator

Output Stage Biasing Calculator

Amplifier Power Required Calculator

Speaker Binding Post
Speaker Binding Post
Speaker Binding Post

Gold Plated
Speaker Connect Posts
4 for $11.48

free shipping

Tube amp transformers
Tube amp transformers
Tube Amp Transformers

Power Transformers
Output Transformers
Custom Wound Transformers
Made In U.S.A.

Allied Electronics
Kester-44 solder
Kester 44 Leaded Solder

For long term reliability

Custom Panel Engraving
Custom Panel Engraving
Custom Panel Engraving

Single Panels
Production Runs

PDF Downloads

The Rejuvenation of Vacuum Tubes
Lane S. Upton

This is a good reference source for those who wish to try bringing weak tubes back to life. It does require the use of a tube tester.

Rejuvenation of Vacuum Tubes PDF

Secrets of Output Transformers
Menno van der Veen

A lot of good information about output transformers, amplifier performance and selecting an optimal output transformer for a special application.

Secrets of Output Transformers PDF

6L6G 6L6GC Datasheet

From Chelmer Valve in Great Britain provides data over a wide range of operating voltages. Use in conjunction with current manufacturers datasheet.  Chelmer still exists, but no longer handles audio vacuum tubes.

6L6G 6L6GC Datasheet PDF

6V6GT Datasheet

There are data sheets that state the maximum ratings for a 6V6GT lower than should be for a stock 6V6GT. This PDF contains maximum ratings for a 6V6GT from a 1961 RCA tube manual. Tubes that are manufactured as 6V6GT should meet these specs.

6V6GT Datasheet PDF

RoHS, beware the Grim Reaper of electronics

RoHS beware the Grim Reaper
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vacuum tube amplifiers
High Voltage Audio
New to electronics or experienced, when working with vacuum tube equipment be careful where you put your hands.

DISCLAIMER assumes no responsibility for damage, injury or otherwise related to any use of information on this site or given by other means. Many electronic circuits, in particular vacuum tube circuits, operate with dangerous voltage and current. Always exercise care when working with electronic circuits.

EJ Jurich has no association with sites offering free downloads of my book. Beware of sites that offers free downloads or want you to register. If the download is free, then why would they require you to register? Free download or torrent sites are notorious for passing malware on to you. Be very careful.

copyright 2014