Burning in is a common term used in audio, which we shall discuss in this article regarding tube amps.
You’ve probably heard people saying that headphones sound better after a burn-in period. For those who don’tdon’t know, this burn-in period refers to users running their headphones at a particular volume level for a certain period to get the optimal sound.
When I bought my first tube amp, I plugged it in, let it warm up, and played. All the tube amps I’ve bought were previously owned, so they have signs of usage and break-in if any.
Now I’ve heard about warming up tubes and biasing tubes, but do tube amps need burn-in periods? This idea was something I was thinking about when planning my next tube amp purchase.
Do Preamp Tubes Need To Be Burned In?
Preamp tubes undergo a burn-in period only to check if they work. Often, tube manufacturers will run these tubes for a certain period to check for any issues before they ship them out to retailers or customers. All you need to do is install and warm them up a little before using them.
To be clear, many guitar players would debate about this burn-in period topic. But for the most part, the only thing you need to do for your tubes is warm them up to get the best saturation.
Do power amp tubes have a burn-in period?
A burn-in period is conducted to test the tubes for power amp tubes. These tests cover checking for defects and the load the tubes can handle. The load is particularly crucial, as these are used to create a pair of matched tubes.
In some cases, tubes aren’t tested for their load, which can lead to having mismatched tubes. Should that be the case, you must bias your power amp tubes.
What are matched tubes?
Matched tubes refer to a set of power amp tubes matched to receive the same load or current. A pair of matched tubes ensure your amp runs at the right level. That means your tubes receive the same current amount so that the amp won’twon’t sound sterile or flat.
If you have a pair of power amp tubes but are not a matched set, then you need to bias your tubes.
What is tube amp biasing?
Tube amp biasing ensures that the tubes in the power amp section receive the proper voltage based on the resistance ratings on the tube. Biasing your tube amp ensures your power amp section is optimized, so your guitar churns out good tones. Biasing the tube amp also provides a longer tube lifespan.
If your tubes are fed a higher voltage than their capacity, you will get a higher saturation, but the tubes will wear out faster. In worst cases, the overvoltage can damage other amp components.
In a previous article, I highlighted the importance of biasing tube amps. As mentioned in the last paragraph, the worst case would be an overload in voltage, which can damage the components of an amp. The least that could happen is your amp sounding too sterile, which results from having a voltage that needs to be higher for the capacity of the tubes.
Biasing a tube amp isn’tisn’t one of those things you can do on your own, unlike adjusting a guitar’sguitar’s intonation. Unless you are a qualified amp technician, tube amp biasing is best left to professionals trained to handle such adjustments.
Remember that capacitors inside your amp can still hold a lot of charges, even when the amp has been unplugged for days. Do not attempt to bias your tubes yourself.
Do all tubes need to be biased?
Not all tubes need to be biased. For one, tubes found in a preamp do not need biasing, as they only need a compatible set installed. Also, not all power amp tubes need biasing, depending on the tube amp wattage. Low-wattage tube amps don’tdon’t need biasing as they don’tdon’t churn out a lot of power.
As a rule of thumb, you don’t need biasing when:
- Your tube amp has a power output of 30 watts and below, and;
- You are replacing preamp tubes.
So, if you’re using an amp similar to the Orange Tiny Terror, you don’t need to worry about biasing.
What do they mean by “warming up the tubes”?
Warming up the tubes refers to heating the tubes in your amp to bring out the best sound qualities of your amp. Vacuum tubes in guitar amps play a crucial role in the overall sound quality. It’s what makes overdrive tones sweeter and gives your guitar more body.
Warming up the tubes of any tube amp is also essential to get a consistent sound throughout usage. While playing your tube amp minutes after turning it on, you can get better tones with the warmed-up tubes.
As a starting point, the best sounds from a tube happen after the tubes warm up for 20 – 30 minutes. That is why some tube amps have a standby switch, which lets you turn off the signal from your amp while you warm up the tubes.
Not all tube amps have the same warm-up time, so it’s best to consult your amp’s manual. And remember that when a tube amp can pass sound, it doesn’tdoesn’t mean it has warmed up. It would need to reach the ideal warm-up time for optimal performance.
How do you prepare new tubes for a preamp?
Replacing the tubes on the preamp section of your amp entails having compatible tubes specified by the amp manufacturer. You will also need a screwdriver to remove any tube covers. And you will need to access the back panel of your amp to remove the tubes.
Now, you don’t need to worry about voiding the warranty of your amp, as tubes are meant to be replaced after a specific time. They’re dispensible components, just like guitar strings.
Before even replacing your preamp tubes, remember that they sometimes go by another name in other countries. For example, a 12AX7 tube is also known as an ECC83 tube in other places. If you can’t find the tube stated by the manufacturer, try looking up the counterpart in your area. It might be using another name.
To replace the tubes in your preamp section:
- Make sure the amp is turned off. Unplug it from the power source and let it cool down.
- Once the amp has cooled, remove the back panel and the tube covers on the tubes. You can pull these gently and turn clockwise to take off.
- Grab your tubes by the base and carefully wiggle while pulling out the tube.
- Get your new tubes, align the pins with the socket, and carefully install the tubes. Do not force the tubes into the socket.
How long do tubes last in a tube amp?
Vacuum tubes should last anywhere between 500 – 800 hours of use. Using your amp regularly in gigs translates to anywhere between 9 – 12 months, depending on the frequency of usage. You can expect longer times if you don’tdon’t always use your tube amp.
As a safety net, any gigging musician who brings a tube amp regularly to all gigs should consider changing tubes before the sound quality deteriorates. That way, tones from the guitar amp remain consistent.
Now if you don’t often use your tube amp, you should know what symptoms your amp will have when you need to change tubes. Signs that your tubes need replacement are:
- Weaker signals coming from the amp;
- The tone from the amp is cut or has lesser bass or treble frequencies;
- Cracking, popping, hissing, humming, or any other unusual sound comes from the amp.
- Tubes do not have an equal glow when compared, and;
- The amp won’t turn on at all;
Now tube replacement isn’t exactly something one should do unless you’re replacing tubes on your preamp section or your amp has a wattage below 30 watts.
Preamp tubes don’tdon’t necessarily need a burn-in from the end user, as manufacturers usually take care of this when they test the tubes for any defects. For the most part, the only preparations you need on your end would be to ensure that your power amp tubes are biased and the preamp tubes have warmed up.
That said, if you’re looking to do maintenance on the preamp tubes of your amp, you don’t have to worry about doing a burn-in, as you only need to warm up the tubes for 30 minutes to get the optimal sound.
John Narciso is a guitar player and music technology hobbyist. He loves exploring guitar effects processors in pedal and plugin format and free music applications. His music preferences tend to be diverse, listening to genres spanning from metal to alternative rock and a little hip-hop.