Picture This: You are on stage setting up equipment for a gig and something just doesn’t sound right. Often, the culprit is a bad tube in your amp. So, when is it time to replace guitar amp tubes?
Many new musicians aren’t even familiar with the inner workings of a tube amp. Tube amps use vacuums or valves to amplify signals from your instrument. When one of these tubes starts to go, music from the amp will often be softer or sound off.
In this article we’ll look into how long amp tubes should last, how you can diagnose tubes and we end the article with a video showing you how to change your amp tubes!
How Long Do Tubes Last?
Unfortunately, there is no simple answer to this question. The average tube life that most manufacturers list is between 1000-5000 hours of usage for preamp tubes. A 4000 hour range is the same as 166 days of playing time.
Power amp tubes have a much better listing range, between 500 and 1000 hours depending on your model.
Since there isn’t a great recommendation for how long your tubes will last, we recommend you change your tubes around the 2nd year (depending on how much you use them) or, always keep fresh tubes with you! The amps that we recommend normally have longer ‘lives’, and quality components is a big part of that, but even the best tubes have a shelf life.
Always having tubes with you is just one more thing to pack, so we normally change our tubes yearly.
Symptoms of an Amps Bad Tube
If you’re not sure if you have a bad tube, there are five main things you can look for that will give you a clue that it’s time to replace a tube.
- 1. Loss in overall volume
- 2. Different colors or a tube looks dimmer than others
- 3. Any popping, hissing or humming that wasn’t there before
- 4. Poor tone being produced
- 5. Amp refuses to turn on.
Diagnosing a Bad Tube in an Amplifier
Remember that amps have two kinds of tubes, preamp tubes and power amp tubes. Preamp tubes are the ones that change the sound of your instrument into an electric signal. They make up your tone or sound you hear when you play.
The power amp is the section that amplifies these signals to a louder volume so it can travel through to your speaker cabinet.
So, How can you check both sets of tubes to find the problem?
A Tube Tester
A guitar amp tube tester is a type of tester that can be used to test the electrical conductivity of vacuum tubes. The basic idea is that the device applies a voltage across two electrodes and measures how much current flows between them.
While this is the easiest way to test tubes, often you can find problems before they go completely bad with some of our other methods.
There are a few visual checks you can do on a tube to diagnose them.
Look for a Orange Glow
The first is their glow. Preamp tubes may have a warm orange glow when they are working properly. However, if the tube is lit up like a light bulb, it could also be going bad.
If you have a purple or a pink glow in your tube it could indicate that a seal is broken or extra gas has entered the vacuum. Both of these are signs that mean a preamp tube has gone bad.
Check The “Getter”
Next thing we want to look at is the “getter”. This is a small silver material that is commonly used to seal vacuum tubes. A light grey or black getter is fine.
You might have a problem with the seal if the getter is pure white. A leak in the vacuum will cause this discoloration and is a clear sign you need to change that tube.
It is much more common for a power issue to come from a blown fuse. If you have checked your fuses and they are fine, make sure your power source is getting good clean voltage.
If neither of these things work, use the visual tests listed above. The third most common power issue is a bad power or output tube. When a rectifier tube goes bad it often blows a fuse, so you may have to change both.
Unusual Sounds from the Amp
As we mentioned earlier, strange sounds coming from your amp could be a sign a tube that needs to be changed. Popping, humming, hissing and a constant crackle all can be caused by a faulty tube.
A lack of frequency range, or a change in output tone is a telling sign that it is time to change out your power tubes. Any reduction in bass, tremble or volume should be addressed by checking the amp’s tubes.
Do Different Tubes change the Tone of an Amp?
There are very minor differences in the sound of tubes. We honestly don’t spend much time worrying about which tube is in our amp!
If you have extra budget, or are really looking for a particular sound, you can experiment with different combinations of pre and power tubes to find which one suits your liking best!
When to Replace Guitar Amp Tubes – The Final Note
The bottom line is: don’t worry too much about the tubes in your amp, but change them when you feel something is going on. Most amps will last a good year or two before needing any attention.
When something strange does happen, hop back to this guide to diagnose the symptoms of your amp tubes and get back to jamming!