If you find yourself reading this page, it’s probably a safe assumption that you’ve encountered some kind of radio interference on your amp and you’re wondering how you can stop it.
Picking up radio signals on a guitar amp is a strange phenomena that most often stems from electromagnetic interference, where your amp picks up radio waves due to improper grounding, inadequate shielding, or the use of poor quality cables. Going through the process of elimination, and finding out which of these issues is the culprit in your case will lead you to the appropriate fix, and will help you to clean up your sound.
In this KillerGuitarRigs Guide, we’ll go into more depth on all of the possible causes of guitar amplifiers picking up the radio, and give you some practical steps and solutions that you can employ to solve the problem. Keep on reading to learn more!
- Electromagnetic Interference
- Guitar Strings as Antennae
- Faulty Amp and Internal Issues
- Role of Cables
- Feedback and Amp Hissing
- Grounding and Electrical Issues
- Fluorescent Lighting Interference
- Radio Signal Solutions
- Corrosion on Contacts
- Control Knobs and Internal Wiring
- Amp Care and Maintenance
- Safety and Professional Help
- Real-Life Amplifier Issues (Case Study)
- Final Thoughts
Electromagnetic interference (EMI) is the leading cause of guitar amps picking up radio signals. In short, EMI is a nuisance signal, one that can find its way into devices that aren’t even intended to pick up signals from external sources – in this case, guitar amps.
These signals can come from any number of sources, including cordless phones, power lines, and of course, radio stations and their antennae. EMI doesn’t just affect guitar amps, of course, in fact almost any electrical device with a speaker can be negatively impacted by this interference, but the sensitive electronics of guitar amplifiers just happen to be particularly susceptible to them.
Having a good understanding of electromagnetic interference is the first step in solving the issue of picking up the radio on your amp. Once you know how these radio waves can make their way into your amp, you’re one step closer to stopping them from doing so.
Guitar Strings as Antennae
As the heading of this section suggests, your guitar strings might actually be acting as an antenna, but what exactly is an antenna? An antenna is a device used to transmit or receive radio waves – if your amp is picking up radio signals, then your guitar strings might be acting as a receiver.
By their very nature, being long and metallic, guitar strings make for excellent antennae. When the length of a guitar string resonates with a particular radio frequency, this resonance can be detected by the pickups, and radio signals can end up playing through your amp.
The solution in this case lies in proper shielding. Installing shielding for your guitar’s electronics and pickups can go a long way towards reducing the amount of radio frequency interference picked up. Shielding is most often in the form of shielding paint impregnated with some kind of conductive material, or copper shielding tape. Both of these solutions can create a barrier to keep out the unwanted signals without negatively affecting the overall performance of the pickups.
Faulty Amp and Internal Issues
It can also be the case that the issue doesn’t lie with external interference, but with internal faults with your amplifier. These faults can be caused by anything from poor grounding to faulty wiring, and in any case, can increase the likelihood of your amp being susceptible to radio interference. A classic example is a loose ground wire or poorly soldered connection acting as an antenna, picking up and amplifying radio signals.
The possibility of internal electronic issues with your amp needs to be considered when you’re in the troubleshooting process. Unfortunately, if this is the case, it’s likely to need the attention of a professional, as dealing with the complicated electronics of a modern amp can be pretty tricky. In some cases you’ll get lucky and find that it’s nothing more than a loose input socket you can screw down and tighten up, in others, you might find that there is soldering or more advanced electronic modification or repair involved.
Role of Cables
The cable you use is another potentially significant source of radio interference. It’s tempting to make an assumption that a cable is a cable, and doesn’t really impact tone, and while its influence on your sound might be subjective, the build quality of the cable, its shielding or lack thereof, and materials used can make it demonstrably more (or less) susceptible to picking up sources of electromagnetic interference like radio signals – especially in the case of longer cables, which due to their length have the potential to pick up more EMI.
Choosing a high quality, shielded cable can make a world of difference. The shielding in these cables (typically copper or aluminum) is specifically designed to protect the signal they carry from external interference. The quality of the conductive material used in the shielding has a significant impact on its effectiveness. Cheaper shielded cables will use thinner conductive layers, which will provide less protection than the thicker shielding you’d find on a more expensive, better quality cable.
Feedback and Amp Hissing
Of course, the nature of electromagnetic and radio interference is so broad and varied, that its effects on amplifiers aren’t always the same. You won’t always hear an actual radio station broadcast, but rather, you might find that radio signals are causing (or exacerbating) feedback, hissing, or humming from your amp.
Feedback is the high pitched squealing sound that amps make when the sound they produced is recaptured at the input source and reamplified. This creates a loop that can swell into a particularly loud and unpleasant sound that, if left unchecked, can actually cause damage to the amp and speaker.
Hiss and hum on the other hand, are constant background noises that can be present even when the guitar isn’t being touched or played. The 60 cycle hum that single coil pickups are notorious for is a great example – these pickups readily pick up on electromagnetic interference (like radio signals).
These issues aren’t necessarily indicative of faulty or damaged equipment, and all guitars can and will suffer from humm, hiss, or feedback at some point, but adjustments to your setup can help you maintain better control. Considering where you position your amp relative to you and your guitar can help to reduce feedback. Upgrading your pickups, particularly in the case of single coils, can also do a lot to improve resistance to EMI and the associated hum. Making sure your equipment is properly grounded will be a big help, too.
Grounding and Electrical Issues
Proper grounding (or earthing) is a critical aspect of any electrical system. A well grounded amp will direct sources of unwanted electrical noise away from the equipment, reducing the impact of any radio interference.
One of the easiest steps you can take to avoid radio interference as a result of grounding problems is to make sure all of your equipment is running on the same electrical circuit. This helps to prevent ground loops, which are one of the most common issues in audio setups. Ground loops occur where multiple electrical devices are grounded in different places, and result in a loop that can both pick up and amplify sources of external interference, resulting in noticeable hum through the amp. By making sure everything you’re using is on the same circuit, this is easily avoided.
Fluorescent Lighting Interference
While not technically a radio signal, the electromagnetic interference emanating from fluorescent lights can also cause issues with guitar amps, and as such should be considered before making an assumption about the definite cause of your problems.
Fluorescent lights work by exciting gas in the tubes with electricity, causing a glow, with electromagnetic radiation being one of the forms of waste energy produced during this process. This is particularly problematic in studios or in large venues where fluorescent lighting is common.
The interference produced is high frequency, which is easily picked up by guitar amplifiers, and generally results in audible (and generally unpleasant) noise. If you find that your amp only hums when you’re playing under fluorescent lights, this might help you to rule out any of the other potential sources. If possible, try to use LED lighting or incandescent lighting, both of which produce far less EMI than fluorescent lights. If you don’t have any control over the lighting, ensuring that your gear is properly shielded can go a long way to reducing these effects.
Radio Signal Solutions
Preventing the pickup of radio signals by your amplifier really does require a tactical approach. Before you go and send it out for repair, or start stripping it down to investigate connections, start small. Try physically moving your amp. Sometimes radio waves are directional, and you may have accidentally positioned your amp in the perfect position for picking them up. A simple change of position or orientation may prevent the reception of the signals by your amp and solve the problem completely.
Additionally, look around for sources of potential interference like power outlets, or other high voltage electrical devices and move your amp away from them. You can also check to make sure everything is properly grounded and on the same circuit. Using a ferrite bead ir RF interference filter on your cables can also be a big help.
If these solutions don’t solve the problem, you might want to consider digging a little deeper to find the source of the issue.
Corrosion on Contacts
If you play your rig outdoors at all, you might have exposed it to increased levels of humidity that, left unseen, can result in corrosion on electrical contacts. Over time, this corrosion can begin to act like a diode, which can cause poor connections, and an increased susceptibility to pick up on electrical interference as it rectifies the radio signals and introduces them to the signal chain.
In this case, prevention is far better than cure. Keeping your amp out of humid environments is a good start, but if you can’t avoid this, be sure that you have it serviced regularly by a professional.
Control Knobs and Internal Wiring
Before you break out the multimeter, you can start to track down the source of your interference by adjusting some of the knobs on your amp’s control panel. The volume and gain controls are the best place to start. By adjusting these controls, and listening to the radio interference you can get a good idea if it’s an internal issue. If the radio signal gets louder or changes as you adjust the gain or volume, this is a good indication that the interference is being amplified by the amp itself, indicating an internal electrical problem.
If the volume/gain knob trick gave a positive result, you’ll want to check on the internal wiring. Due to the vibrations an amp experiences, over time, wiring can wriggle itself loose, and over extended periods, wire can actually degrade and shielding can become less effective. Opening up the amp to check these can reveal a whole host of issues – as always, though, if you’re not confident when it comes to electronics, we’d suggest letting a pro take a look as amps deal with dangerous voltage levels.
Amp Care and Maintenance
Proper care and maintenance of your amplifier can prevent many of the issues that can cause the reception of radio interference. In general, maintenance includes regular cleaning, checking for loose connections, and making sure that internal components are properly shielded.
Routine maintenance is not only the first step in reducing or preventing interference, but it also helps to prolong the life of your equipment. This maintenance can help you to see issues before they develop to the level at which they would cause a problem.
Safety and Professional Help
We can’t reiterate enough that if you’re not familiar with working on electrical or electronic equipment, that you seek professional help from a technician or repair specialist before attempting any repairs on an amplifier. Tube amps in particular can store harmful voltages even after they’re unplugged, putting you at risk even if the amp appears to be safe to work on.
Safety should always be your top priority. When dealing with electrical repairs, there’s a risk of electric shock, which can be potentially fatal. Professional technicians have the knowledge, tools, and experience to handle these risks appropriately.
Even if you aren’t in danger, poking around the electrical and electronic components without knowing what you’re doing can cause further damage, exacerbating the problems you already have, or creating new ones that might not appear right away.
Real-Life Amplifier Issues (Case Study)
One of the best examples we’ve ever come across of an amp picking up radio signals was in this JRock Projects video on YouTube. A Peavey amp was being used to test capacitors for a vintage radio, and during the tests, the amp started picking up a local radio station. It wasn’t static interference, and actually varied depending on the positioning and movement of each capacitor being tested. This particular case pointed towards an internal issue within the amp itself, as there was no guitar in the mix.
After a deeper investigation, even more strange behaviors were discovered. The most notable being that when the transformer at the back of the amp was touched, the sound output distorted significantly, which was the second piece of evidence pointing towards an internal issue with the amp’s electronics.
The amp was fully inspected, and when checking the input jack, the culprit was found. It was discovered that the jack had started to come away from the printed circuit board (PCB) that it was attached to, and not only that, but several of the solder joints had broken, too.
To fix the issue, silicone caulking was used to provide support between the jack and the PCB. This solved two of the problems present – it secured the jack more firmly in place, and subsequently helped to prevent further occurrence of the RF interference issue by creating a more stable connection. One of the biggest points to understand here is that the physical construction quality of the amp can have just as significant an impact as problems with the electronics.
So, what’s the takeaway? Solving a problem like reception of radio signals through an amplifier really does involve a holistic approach. Internal and external factors both need to be considered, and we shouldn’t rush to any automatic assumptions about the cause of the issue.
Modern guitar amps are far more reliable than amps of years gone by, but that doesn’t mean that they aren’t susceptible to picking up radio interference. If anything, amps are more electronically complicated than they’ve ever been, which means that if yours is picking up some kind of interference, there’s a whole host of potential causes that could be at the root of the problem.
Throughout this guide, we’ve explored a variety of solutions to address the issue of guitar amps picking up radio signals, from simply moving your amp, to checking and tightening connections, using high quality shielded cables, and making sure that your equipment is properly grounded. Remember, each situation is unique, so it might take a combination of these methods to completely eliminate the radio interference you’re experiencing. You also shouldn’t overlook the importance of simply maintaining your amp.
If it’s a newer amp, check the warranty details – you might be able to get it professionally repaired at no cost, and, as we mentioned throughout, if you’re not experienced when it comes to electronics repair, and the simple steps didn’t resolve the problem, take your amp to a qualified tech or repair person.