Valve and tube Frequently Asked Questions

To provide a little context for the site and explode some common myths I have drawn up a short list a "Frequently Asked Questions". If you have other questions you feel should be answered here, please email me at: To use this email address you will need to re-type it and I'll see if I can add these the list.


Isn't this site taking valves a bit too seriously?

Yes - definitely! Thanks to my friend Adam for pointing this out :)

By the way, Adam is the guy who persuaded me to build a Hartley oscillator with the 1 kW GM100 triode and so he's not blameless in all of this...


Aren't valves (totally) irrelevant today?

Good question, two part answer: In terms of mainstream consumer electronics and computers certainly yes.

In some specific applications no:

The majority of television sets still use a "Cathode Ray Tube" to display the picture, these are a large glass valve using special phosphors that emit light when struck by a stream of electrons.

Microwave ovens employ as special type of tube known as a cavity magnetron. These are cheap to manufacture and generate hundreds (or thousands) of watts of microwave radio frequency energy that heats your food for you.

Magnetrons are also used in some RADAR systems and it was this application that spawned their design in the early 1940's.

Many people really like the "valve sound" for their hi-fi and electronic instrument amplification and so valve audio amplifiers have gained a definite main-stream following.

Valves are still used in commercial broadcast stations where huge amounts of radio frequency power must be generated.

For the electronics and radio enthusiast, valves offer a chance to make some beautiful, functional and excellent pieces of equipment and possibly to engage in some serious nostalgia.

There are a number of enthusiasts collecting rare types of valves. Some antique or unusual types can command a very high price. Generally these devices will not be used but will be displayed (one hopes).


Are valves still made today?

Yes. Businesses such as Eimac make power valves, some devices being able to generate more than 1 mega watt of power. Smaller valves are manufactured by Russian, Eastern European and Chinese firms.

Large quantities of New Old Stock or "NOS" valves are still available. These are valves that were made years ago but have never been used and are often still in the original packaging - assuming this hasn't rotted!

Because there are valve amplifiers and radio equipment in use today, a number of retailers are active in providing good stocks of valves for sale to individuals.


Aren't valves unreliable?

Contrary to popular belief valves can actually last quite a while. All valves do have a finite lifetime but this lifetime can be measured in thousands of hours for many parts and so can perhaps they should be regarded as "service items" rather than just plain unreliable.

Power valves do wear out over time and broadcast types are generally replaced according to a strict schedule to ensure total equipment reliability. Low power valves (often called receiving valves / tubes) will generally last a very long time unless they "go soft" (air gets in or gas gets out of the metal parts inside) or the filament breaks due to mechanical or electrical fatigue.

The life of low power valves is thus mainly dependant on the quality of manufacturing and their subsequent treatment. Many types can exceed 10's of calendar years of moderate usage in well designed circuits.

For example, my 1955 Pye radio has all but one of its original valves in it. I suspect if the valves were tested in a tester they would not all measure as 100% but the radio still works fine and so for now I'll leave it well alone!


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