How to Connect Tube and Amplifier
Tubes are the heart of your amplifier. They amplify your guitar’s signal and create the tone that you hear, but they can go bad, or break down, so it’s best to know what to look for and when.
There are many different types of tubes out there, from pentodes to triodes and more, so it’s important to understand what they do so you can understand how your amp’s working. The most common are EL84 power tubes which are used in a huge range of amps.
The most obvious thing you need to know about your tube is that they are very sensitive. They can fail if you don’t replace them in time, or if they’re too hot. That’s why it’s always a good idea to check your tubes regularly, and if you see a warning light then it may be time for replacement.
A few things you should keep in mind when connecting tubes and amplifiers
First, make sure your amplifier is unplugged and has been turned off for a while before starting. This will avoid any chance of damage to the tube and allow you to work safely.
Second, don’t touch the tube – it gets hot and you don’t want to burn yourself! Using safety glasses, short sleeves, and removing any rings or jewellery is also a good idea.
Third, take note of the ‘getter’ (the silver coating on top of the tube) as this will help you tell if the tube is operating in a vacuum. If the getter is white then it means air has leaked into the tube and will need replacing soon.
Fourth, if the plate of the tube glows red then this is a sign that there’s too much voltage swing on it. This can cause your amplifier to sound harsh, and will soon die out if you don’t change the tube quickly.
Fifth, check your bias is set correctly – it’s important to get this right as it can have an effect on how long your tube lasts. Too low a bias can mean your amp sounds thinner and less dynamic, while too high can have a negative effect on how loud it is.
Sixth, rebias your tube before you start playing with it
As mentioned earlier, tubes are very sensitive to voltage swing, and they can become damaged if they’re not re-biased properly. This can make your tube sound harsh, and can also affect how well it works. If the bias is too high then your amplifier will run hot and won’t sound as good, so it’s important to check that it’s not too high before you start playing with it.
Seventh, check your power switch is working – if it’s not then there’s a problem with your wiring or something in the box. Hopefully the problem is not your tubes as this can be very difficult to spot.
Now you’ve got some basic knowledge of what tubes do, it’s time to learn how to connect them to your amplifier. This isn’t as hard as it looks, and we’ll go through a few basic steps so you can make sure your amp is working smoothly again.