Inevitably the time will come that you need to change the tubes in your guitar amp. But how do you know if it’s actually time and the tubes are indeed bad? While tubes are not always at fault for causing issues, they are often the source of amplifier problems. Luckily, guitar amp tube replacement and installation is pretty straight forward.
The following guide will give you some important info to help you determine if it’s time to swap those old valves or not. As always, please pay special attention to the safety disclaimer below.
Tube guitar amplifiers are capable of creating lethal voltages and can store these voltages well after the amp has been turned off. Also, many components such as tubes can become very hot and unsafe to handle. Please exercise extreme caution when servicing amplifiers! If you are uncomfortable working with your amp in any way, take it to a qualified technician.
Symptoms of a bad tube
First, how does your amp tell you that something is wrong? If you pay close attention with your eyes and ears, you can usually tune in to any issues your amp may be having. Here are the best signs to listen and look out for.
Your Amp Sounds Different
I have experienced first-hand that unsettling day when your amp no longer has that killer tone you loved. Depending on how long it’s been from the last tube swap, it could be time again. Tubes only sound their best for a set amount of time relative to how often you play. (The more you play the faster they wear out.)
If it has been a while, it may be time to change your tubes even if nothing is technically wrong with them. You certainly don’t have to, but your tone will thank you for it.
Something Sounds Wrong with Your Amp
Occasionally your amplifier won’t sound different, it will sound like something is downright wrong! Certainly, something could be wrong, but it’s ok! Things happen, parts wear, and it is likely fixable by changing out one or more tubes. Especially if the sound was not present before, noises such as unexpected hum, hiss, crackling, or overt distortion could be the signals of a failing tube. Always be perceptive to what your amp is telling you.
The Amp Makes No Sound at All
When your amp doesn’t make a peep, it is possible that a connection has separated inside a tube. Even though modern tubes are well made, things can always go awry. Tubes have many sensitive connections inside of them. If one of the joints separates, it is possible that the valve will not pass any audio. If this happens your amplifier will power up as usual, but no sound will be coming out of the speaker.
Intermittent loss of Power and/or Volume
Intermittent problems are always the most difficult to solve and deal with. I have experienced amplifiers that will have volume or power drop in and out with the level being normal for a while then drastically reducing only to eventually return again. This can be a symptom of a dying power tube that is still trying to hang on.
The tube can operate normally for a while, then begins to fail causing the power or volume drop. Eventually the tube catches up and operates normally. Any tube behaving in this manner must be replaced. However, all intermittent issues should be thoroughly investigated due to their difficult nature.
Your Amp Won’t Power On
I have also been in this situation, and it just plain sucks. It’s scary and panic begins to set in seeing that you have a gig that night. When your amp won’t turn on (assuming all operator error has been accounted for, i.e. the amp is indeed plugged in) it is often evidence of a blown fuse.
As I mentioned before, if something fails within a tube, problems can ensue. If a tube fails and creates a short circuit, the fuse will blow to protect your amp. While a blown fuse does not always indicate a short, nor does it tell you where in the amp a short may be, a short within a tube may definitely be possible.
What to Check For
We have determined what symptoms may be demonstrating that your amp tubes are bad. The second course of action is determining if it is actually tube failure that is causing said issues. These are the key signs to look for before performing guitar amp tube replacement.
Is the Tube Filament Glowing?
We all love that orange tube glow. It’s one of my favorite things about tubes! But if a tube isn’t glowing, something isn’t right. Tube filaments don’t have to glow very bright, but that glowing is part of how they function. If the filament is not glowing, that is a good indicator that the tube is not being heated properly and will therefore not pass signal.
That being said, when a tube filament is not lit, that does not guarantee that a bad tube is the culprit. It could actually be a different component within the amplifier has failed, and now the required voltage and current are not being provided to the tube. This is something to keep an eye out for though.
Is the Getter OK?
What is the getter? Getter is the silver/grey coating on the top, inside of the tube. Without having to get into too much detail about how getter works in this article, it can be a key indicator of tube health.
As we know, tubes work because they operate in a vacuum. If this vacuum is compromised, i.e. the valve is cracked, air will leak in and the getter will turn white in color. So, if you see any tubes where the getter is white, it is mandatory replacement time.
Tube Red Platting
This is definitely uh-oh time. Tube red platting is never normal and the amp should be turned off immediately if you spot this. Keep in mind that red platting occurs on the plate of the tube, not the filament, so don’t confuse this with normal tube glow.
Red platting is an indication that too much power is flowing through the tube. Typically, this is a symptom of an incorrect bias adjustment, but occasionally this is an indicator of a failed or shorted tube. Be sure to check and possibly re-bias your amplifier if red platting ever occurs.
Blue/Purple Glow Inside Tubes
I have encountered many guitarists that believe they have faulty tubes because they have a blue/purple glow. This is perfectly normal in modern tubes and especially in large valves such as 6L6. Occasionally, purple glow near individual elements can indicate an air leak in the tube, but this is much less common than the normal glow near the glass. I wanted to include this tid-bit here as it is easy to confuse this for a bad tube. The blue/purple glow sure is pretty though!
One way to understand if a tube is bad is to test if it is microphonic. A microphonic tube will amplify physical vibrations in addition to an electrical signal. If a tube has this problem, it can create all kinds of noise that gets mixed in with your signal.
Luckily, there is in easy way to test for microphonics. While the amp is on, take a pencil or chopstick and gently tap on the tube. If a loud, pingy, ringing sound is audible, you have found a microphonic valve. Always be careful when working on a guitar amplifier than is turned on! Those tubes get very hot and nobody wants to get burned!
What if Nothing is Visible?
If you are experiencing issues with your amp but everything looks to be in order, it is likely time for some process of elimination. One by one you can pull a tube and replace it with an identical tube that is known to be in good working order. If any tube is removed, and a newly installed one alleviates the problem, you have very possibly found the offender.
When doing this, make sure you are turning the amplifier off before removing and replacing a tube. Also, be sure to give tubes plenty of time to cool down before touching them. Sometimes tubes just don’t visually show that something is wrong, and process of elimination is the only answer.
How to Fix a Verified Bad Tube
There is only one way to fix a tube once you have verified that it is bad, you have to replace it. Thankfully though, modern tubes are easy to find and not ridiculously expensive (the price and availability will obviously fluctuate depending on the tube type). Simply ensure that you are replacing a tube with the same model.
Some tubes, such as power tubes, will occasionally all need replacement if even one is found to be bad. This is because power tubes are often “matched,” meaning they exhibit similar characteristics. You don’t want to run one brand new tube and one old tube if they are intended to run identically. Also remember that power valves may need re-biasing (depending on your particular amp) after they have been replaced.
Guitar Amp Tube Replacement
If you have never installed a new set of tubes before, don’t worry, it is a pretty straightforward process. That being said, there are a few things to look out for.
First, always ensure that you are replacing tubes with the same tube type. For example, if you are replacing a 12AX7, be sure to re-install another 12AX7. If you are replacing a 6L6 power tube, be sure to re-install another 6L6. There are some exceptions to this rule, but stick to the basics for now.
Make sure that you turn the amplifier off and allow the tubes plenty of time to cool down. Changing tubes is quite similar to changing a light bulb. If the light has been on for a while, the bulb is simply too hot to touch, and you must wait for it to cool down first.
Removing the Tube
Firmly grab the tube near its base. Be firm but not overly tight (they are made of glass after all.) Gently rock the tube back and forth while pulling it up out of the socket. The rocking helps loosen the tube as they are generally too tight to simply pull out.
The same process is used in reverse while installing new tubes. Before you insert a new tube, take note of the pins on the bottom. You will see that on noval tubes, one of the pins is missing. There is also a corresponding missing socket space as well. This is how you ensure you are inserting the correct pins into the correct socket, there is only one way to do it!
On larger octal tubes, you will see that the phenolic base as a plastic key on it. This notch has a corresponding opening on the socket. This is how larger tubes ensure correct alignment.
Inserting the Tube
Now firmly insert the tube into the socket ensuring correct alignment. Gently rock the tube back and forth to allow for easy insertion. You will find some resistance and that is normal. However, never force a tube into a socket that is not going in! It is likely that the tube is misaligned. If you force this too much, you will end up with a hand full of broken glass!
Simply repeat this step with all remaining tubes. See, guitar amp tube replacement isn’t so bad after all!
Where Can You Buy Tubes?
There are many reputable tube retailers online. What you want to ensure is that you are purchasing a brand name tube of the correct tube type. Prices can vary greatly depending on brand, vendor, and quantity being ordered.
I personally like purchasing tubes from Reverb.com. They have an incredible selection with offerings from many different vendors. They have several different brands available, at many price points to suit your needs.
Vintage vs. Modern Tubes
You will definitely run into the debate of using vintage or modern tubes. Vintage tubes are extremely sought after. They are incredibly well-made and many people find them sonically superior. That all comes at a hefty price though and very limited availability.
Modern tubes can be well made, and certainly brand name products typically are. However, there are also plenty of terrible valves out there in current production. These are the tubes you find with no brand name and only have “China” printed on the side. Some modern tubes sound quite good, while others don’t (it’s mainly user preference). All that being said, modern tubes are definitely easier on your wallet!
Which to Choose?
Unless you have an original ’65 Deluxe Reverb or you have more money than you know what to do with, I am recommending modern tubes. Just make sure you stick with brand name products and feel free to experiment to find out which sound best to you! If you play regularly and gig with your amp, you want a good reliable tube working for you. Not to mention a back-up or two as well.
If you are an amp collector, you probably want to find vintage (and period correct) tubes. This isn’t so much for sonic reasons as it is for authenticity in a collector’s piece. If you are looking for the ultimate tone, many suggest vintage tubes. While they often do sound incredible, I do not find they sound so much better than modern tubes, as to warrant how expensive they are.
There is no real right or wrong answer here. It largely depends on your particular circumstance and what you are trying to achieve. Either modern or vintage tubes could sound great in your amplifier.
What if Your Amp is Still Having Issues?
If you have diligently gone through the steps above to no avail, it is quite possible that something other than a bad tube is causing the problem. Guitar amplifiers can often have many different things that exhibit the same symptoms when they fail.
If you’re are comfortable and capable of opening the amp up to further troubleshoot the problem, now is the time. However, if you are less experienced, I would strongly recommend taking your amp to a certified technician for repair.
When working on the internal components of an amplifier, please always remember that guitar amps are capable of storing lethal voltages well after they are turned off. If you are unsure on how to safely work on an amp, please just take it to a technician, and they will be happy to help you.
Hopefully this article has given you some helpful tips and insight for guitar amp tube replacement. By keeping an eye and ear out, your amp will usually tell you when it is time for a change. Just remember that tubes are easy to replace and that luckily nothing else is wrong with your amplifier! By maintain tubes as needed, your amplifier should keep cranking out amazing tone for years to come.