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Dealing with harsh, unwanted noise from your tube amplifier?
Where do you start if you want to investigate the problem?
Check out our comprehensive troubleshooting guide for a crackling tube amp.
As the title suggests, this article is a look at one specific problem, “how to fix a tube amp that crackles.” This annoying problem is all too common, and we have a variety of suggestions on how to fix it.
As with any other problem, it is important to be calm and methodical in fixing the issue, checking one potential cause at a time until finding the solution that works. Some fixes may require extensive technical knowledge of amps; others can be done by anyone with a basic understanding of amps.
First of all, we need to look at what a tube amp is and how it functions.
It’s important to take just a moment to remind ourselves of safety issues related to fixing amplifiers.
There are various components inside amps that can store an electrical charge and kill you, so probing around inside an amp haphazardly is a bad idea. You need to focus on what you are doing at all times.
A good tip when probing inside a live amp is to keep your other hand in your pocket. If you make a mistake, it is the electric current flowing across your heart that kills, so keeping the other hand inside your pocket redirects the electricity to miss your heart.
Remove jewelry of all kinds. You don’t want metal attached to your hands and body.
Always unplug an amp before you start to solder.
Be sure to use fuses that are the correct rating. It is cheaper than blowing up your amp.
Wear safety glasses.
Electrolytic filter capacitors can retain electricity charges, so always discharge them by shorting the plus side to the chassis.
Turn the power off before discharging electrolytic filter capacitors.
Tubes will burn. They get very hot, so do not touch them.
Do not install tubes with the power connected. The glass could shatter, and you might then touch high voltages.
Having the right tools handy makes working on your amp much less stressful. If you are a professional musician, your amp is vital to your livelihood, so taking a simple toolkit and spare parts around with you is always good practice.
Your tube amp will always find the most inconvenient times and places to act up and stop working. We’ve come up with a handy list of tools that will make sure you’re always equipped to fix issues that may arise in your tube amps.
Small flat-blade screwdriver
Standard flat-blade screwdriver
Lubricant free contact cleaner and lubricated contact cleaner
One foot speaker cable with 1/4 male to female jack
1/4-inch female to female mono adapter
*Specific tube types vary from amplifier to amplifier, so always check the specific model of power tubes, preamp tubes, and rectifier tubes that fit your amp via the schematic or diagram (it’s frequently labeled inside the amp).
Finding why your amp is making a crackling noise is never easy. Some professional technicians even have trouble with this because there are so many different things that can cause crackling to occur.
The first thing to do is to identify what type of crackling you’re encountering by analyzing a few key variables.
Types Of Amp Crackling
If the sound is very much like a rumbling noise, it suggests that the possible cause may be a faulty output tube. Lightly hit each tube with a pencil or drumstick or another wooden tool, something that doesn’t conduct electricity.
If one of them produces the crackle, this may well be the culprit. So just replace it and the problem is solved. However, a better solution would be to replace the complete set of power tubes in your amp, because keeping your power tubes “matched” in brand and age generally works best.
If this does not solve the problem, then return to troubleshooting.
Glassy and/or High Pitched Crackle
If the crackling is higher in pitched or “glassy” sounding, all signs point to the preamp tubes. Start at the preamp tube closest to the output tubes, and one by one, lightly hit each tube with a pencil. If one of them produces the crackle, this may well be the culprit, and you should replace it.
This may fix the problem, and you can have a quick celebratory dance, or it may not, in which case we continue the troubleshooting process.
Loud Crackles That Sound Like Static
This could be a sign of interference or dirty connections. Methodically check EVERY single connection, including tube sockets.
Clean each one thoroughly as dirty connections will cause static sounding crackles.
Random Crackling and Pops
This typically signifies your amplifier has faulty power tubes. First, try swapping them one by one with a spare tube. If this does not fix it, then the preamp plate and/or cathode resistor need to be checked out (this is probably something to get a professional tech to do).
Connections Between The Speakers and the Amplifier
Sometimes the problem has a simple solution. The connection between the amp and the speaker may be shoddy and causing interference. In this case, simply replacing the cable or wire between the amp and speaker to solve the problem.
It can be very frustrating to pull apart your entire amp bit by bit, replacing components, only to discover the entire problem was simply a bad wire, so this is often a good thing to check first when you hear crackling in an amp.
It could be that a small piece of solder has come loose and is providing an intermittent connection. Take a close look inside and check out any of the visible soldering and see if any of them are loose or appear to be “cold” solder joints.
You can tell a cold solder joint by looking for any contacts that appear “lumpy” or rough on the surface. In cheaper amplifiers typically made with a printed circuit board, lower quality workmanship in manufacturing can frequently result in some less than ideal soldering jobs, so bad solder is always something to look for and rule out if your amp has a crackle.
1. Turn Down Internal Effects
Turn down any internal effects that come with your amp (e.g., tremolo and reverb). Turn down all the volume controls. Now comes the technical part, “Hit the top of the amp with a fairly large blow.” If this causes the crackle, listen carefully to it. Remember how it sounds and then skip to the solutions in the next section. If it does not result in the crackle, then turn up the volume and hit it again.
2. Give Your Tubes a Quick Pull
I love simple solutions, and it may just be that you need to give the tubes in the amp a pull. Of course, you should only do this while the amp is turned off, and unplug it for safety! Wait for all components to discharge electricity properly before doing anything else.
This quick pull can sometimes reseat a tube’s pins and provide a better connection. If this is the case, then the crackle was simply caused by a slightly incomplete connection within the pins of the tube socket.
3. Clean Your Connections
Related to the last point, it can be a good idea to clean ALL the connectors in your amp. If this cleanup does not fix the problem, you could try to swap every connector in the amp (which is a hefty job!). Do this carefully and thoroughly. If you still have no success, after you have finished stomping your feet with anger, you should move onto the next point.
4. Check Your Amp’s Power Supply
Possibly your power supply is the villain of the piece. I do not just mean the power supply inside the amp itself, I mean where you plug your amp in at your house or studio. So try plugging in the amp somewhere else.
First, try another socket in the house. If the noise stops, then maybe there is some problem with the socket or circuit generating the crackle. If it does not stop, then try another place entirely.
If it continues, you will at least know the problem is inside the amp. If it stops, then you can start to investigate issues in the wiring within your house or studio, and not your tube amplifier.
5. What If It’s The Knobs But Not The Amp Itself?
If the crackling occurs when you touch your amp knob, the problem is most likely a build-up of carbon dust on the potentiometer. A quick temporary fix is to clean it with an electronic cleaner spray. A more permanent fix is to get a new knob from the manufacturer.
You need to ensure the pot matches the faulty one for safety and to keep your amp’s tone the same.
If All Else Fails, Revert To A Technician
Any good technician should be able to listen to an amp crackle and almost instantly know what the problem is, or will at least have an idea of where to begin looking.
A good technician may also suggest that spending more money fixing a cheap amp is not a good investment, because the reality may mean that the money spent on parts and labor fixing the current amp may be better suited towards just buying a brand new amp.
Much like determining when a car is “totaled,” sometimes amps need to go to the great gig in the sky when the cost of fixing any problems outweigh the functionality and overall value of the amp.
Best Practices To Keep Your Amp In Top Shape
You can expect that your amplifier will have an expected period between services of up to 10,000 hours of use. Some guitarists routinely replace tubes in amplifiers every two years, whether there is a problem or not. Other musicians may not do anything until the amp gives up.
Again, car maintenance is a good analogy; some like to get their oil changed every 3000 miles as recommended, some wait until the car is about to fall apart to take it in to get fixed.
Some musicians build an almost superstitious attitude to their tubes and refuse to change them until they have to if “bad things happen.” Ultimately, tubes are just a part (and one with a finite lifespan at that), and they will need replacement at some stage.
The question is, do you want this to happen at some random moment when a failure occurs, or do you want to be prepared and change them during scheduled maintenance?
Your tubes should function for around 10,000 hours with regular use, and whether you like it or not, there is a strong chance that they can fail at any time after that. If you are proactive and regularly have your amp worked on (at least once a year if you gig out consistently), you will likely continue to have amps that work night after night and hopefully remain crackle free.