One of the most common questions we get asked is why is my amp starting to sound a bit noisy these days – and are the valves likely to be the culprit?
The first step is to identify whether we are talking about hum or other weird noises like crackling, popping, or squealing?
Let’s look at hum first.
Why does my amplifier hum?
Hum can be a real pain in the proverbial for guitarists so lets start off by looking at what can be done to eliminate some of the causes. Yes, hum can be caused by failing valves but there are some basic tests that need to be done before we start looking for culprits.
The first check you need to do is to eliminate every part of your sound chain AND the electrics in your house before blaming the amp.
To do this, remove everything from your sound chain except for the amp and the mains lead. That means all extension leads, all four-ways, all pedals and even your guitar lead have to be removed leaving just the bare amp and its power lead.
Plug it in. Does it hum?
Now add a guitar and a lead, ideally a short high quality lead, not something cheap that’s been knocking around for years. Now repeat with a different guitar and a different lead. If you don’t have one get your mate round with his. Guitar leads are notorious for adding noise to your sound chain.
Now take the rig to a different floor of your house or to a different building (again your mate might be useful for this as well). What we are trying to identify is whether there is an electrical issue with the mains ring you are using in your house. Some electrical appliances, even something like a fridge, can put a small signal onto the main which your amp will pick up and amplify.
You can’t begin to imagine how many so called hum problems I have solved for readers using the above technique.
Nah, didn’t work, I’ve still got hum on my amp.
Okay, before we move on, bare in mind that some amps are a little noisier than others. I recommend you do a little bit of research on line to see if this is a common fault with your amp. Sitting in a bedroom just a few feet from an amp can also make an amp to appear to be a lot noisier as well.
Next in the line of possible culprits is, of course, the valves.
As valves get older they get noisier. If you haven’t changed your valves for a while this is the next step.
If you have a valve amp, you accept you have to change the strings in order to maintain the perfect tone. Similarly, if you have valve amp, accept the fact that you need to change your valves every 500 to 1,000 hours of playing if you don’t want it to sound dreadful.
Sometimes the valves will last longer than this, sometimes less depending on a whole range of factors I shan’t go into here but obviously the amount of lugging around they get is a big factor. Obviously if you gig you will get through more valves.
If you are a gigging musician, never go out without a spare set of valves. It’s not fair on the others in the band and it’s not fair on the audience either. At the very least carry a spare preamp valve (ECC83/12AX7) for emergencies.
I’ve got other noise problems on my amplifier – not hum
Not always, but certainly over 90% of the time, new noise means you need new valves.
Old valves will often start to complain before they blow. Not always, sometimes they just blow unexpectedly, but usually you will get a few warning noises. The most common ones are described as pops, squeals and crackles. A drop in volume is another common symptom.
You can replace your valves yourself very easily. If it solves the problem – great. If it doesn’t solve the problem, at least you have removed one of the most likely causes. You have also saved yourself the labour fees and markup fees on the valves at the same time.
Most of our customers change their valves themselves.
The only thing you need to remember is that amplifiers can carry a very high voltage long after they have been switched off. This should not be a problem provided you don’t go poking around but if in any doubt, simply leave the amp unplugged for 2 to 3 days before changing your valves. If you are hyper cautious you can always do what my amp tech does. He always stands on an insulating mat (a rubber one from the car or garage is fine).
A new set of valves will also show up just how tired your old valves have become. Unfortunately it’s a very gradual process and you don’t notice the deterioration until you pop a brand new set in – and whoaaaaah, suddenly everything comes alive again.
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