DIY Vacuum Tube Amplifiers
Same old technology, same great sound
Hosted by EJ Jurich

DIY Vacuum Tube Amplifiers
Same old technology
same great sound

Hosted by EJ Jurich

All Triode Class A Stereo Amplifier Kit

A project is in the design stage for an all triode Class A four watt per channel stereo amplifier kit based on a 2019 experiment. Four watts may not sound like much power, but when paired with more efficient speakers, you can achieve appreciable volume.

Why Only Four Watts?
For home audio systems, operating high-power vacuum tube amplifiers can be expensive. Besides the initial cost of the equipment, there is the cost of replacing more expensive, higher power tubes as they 'wear out'. Also, higher power amplifiers draw more current with an associated higher electric bill.

Why Triodes?
Pentode power tubes are significantly more load sensitive than triodes. Speakers are impedance rated at 1,000 HZ. Depending on frequency, the impedance value then skews above and below 1,000 HZ. Because of frequency related impedance variations reflected back to an output tube plate, pentode load matching can skew off the impedance matching curve. Impedance skewing can cause various speaker systems to sound dramatically different. Triodes maintain a better match over a wider impedance range.

Why Class A?
Operating Class A single ended in itself provides a more natural sound than push-pull operation. The push-pull signal splitting phase inversion, then blended back together process is not perfect to begin with. Component values and tube characteristics that change with age add to signal errors in a push-pull system.

The Allure of Vacuum Tube Amplifiers

There are a few possible reasons for the allure of vacuum tube amplifiers. Perhaps it is nostalgic, a 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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Costs Consideration

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. For the audiophile working on a home system, referring to sound pressure levels for loudness can save you money and save your hearing.
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Capacitors are available in many flavors, from low-cost general purpose capacitors to high-end Audiophile grade capacitors that can get very costly. Searching audio forums, you will find discussions as to which capacitors sound better. Rather than select capacitors based on subjective opinions, you might consider capacitors from a technical viewpoint.
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Design For Tube Rolling Half Watt 6SN7 Headphone Amplifier Vacuum Tube Gain Controlled Amplifier PDF

Vacuum Tube Amplifier Basics

The book is no longer published through Amazon. Older used copies of the book may not include updates. An updated version of the book in PDF e-Book format should be available by the end of summer 2024. There are no plans for a print version at this time.

vacuum tube amplifier high voltage danger
vacuum tube amplifier high voltage danger

Danger High Voltage!

Depending on tube type and circuit design, vacuum tubes operate with higher voltages, up to 500VDC and possibly higher. 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 voltages and currents. Always exercise care when working with electronic circuits.

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