Vacuum Tubes

Vacuum tubes control the flow of electrons in a vacuum and are used as an amplifier, a display screen, or a switch. These tubes were used as on/off switches for the first computers. They were invented by John Ambrose Fleming in 1904. These kinds of tubes were used in the 1930s and 1940s. Vacuum tubes eventually were replaced by transistors. The transistors are smaller and are used in the electronics we use today such as our phones and computers.

These tubes undergo a basic principle of thermionic emission. As metal is heated, thermal energy will bump electrons loose. Once the cathode is heated and the anode has a positive voltage applied, electrons will be able to flow through.

When do I change a tube? For power tubes, you should change them around one to two years. If a lower output is noticed or you hear different noises, the tubes more than likely need replacing.

Is a tube that is glowing blue defective? This does not appear to be a defective case as it is an effect of a power tube, and is also part of the blue spectrum. This is an indication that the vacuum is operating very good, rather than a defective part.

How long will these operate before they need replacing? Check out this information below from Upscale Audio - “Power tubes like EL34’s and KT88’s are good for about 2500 hours or more. But may go longer in an amplifier with a conservative design. Small signal tubes with numbers like 12AX7, 12AU7, and 6922, and rectifier tubes like 5AR4 may go 10,000 hours.” (

Here are some disadvantages of using vacuum tubes:

  • Larger in size for portable products.

  • Use a higher voltage in most cases.

  • Higher power consumption.

  • More prone to breaking due to glass tubes.

To find these vacuum tubes on our website, please use the following link - This will direct you to the products we have to offer.