Even after all these years, a surprising amount of guitar players still prefers tube-driven amplifiers. Although the technology is pretty much archaic at this point, there’s a lot of favorable traits they bring. However, they not only come with a higher price but also require special care and maintenance. One of those maintenance procedures is biasing.

But what is amp biasing and how much does it cost to get amps biased?

Well, these aren’t exactly the simplest questions to answer. Electronic biasing refers to the direct current voltage applied to a terminal of an electric component in a circuit where alternating current is also present. The idea is to establish proper conditions so that a specific component could operate normally.

If we’re talking about vacuum tubes in a tube-driven amp, bias is a direct current voltage supplied to a tube that controls the flow of electrons within itself when there’s no guitar signal present. A bit complicated, right? Well, I’ve said that it’s not the simplest question to answer.

The price differs depending on a few factors. However, in most cases, biasing should be anywhere between $25 and $100. It varies depending on what you need.

Anyhow, let’s dig deeper into this topic and find out more about amp biasing. The whole thing about tube amp biasing does seem a bit confusing, even scary. But we’ll try to bring it closer to an average guitar player. So let’s get to it.

What Is Tube Amp Bias?

First off, how would you define amp biasing? We’ve mentioned the DC voltage applied to an electrical component in a circuit where AC is also present. When it comes to tube-driven amps, it’s a process that makes sure that tubes are working at their optimum capacity. Essentially, it keeps the right voltage being fed into the tubes.

Open amplifier with vacuum tubes

One important thing to note here is that bias tweaking is only about tubes in power amp sections. There’s absolutely no need to bias preamp tubes. In almost all cases, preamps in tube amps have self-biasing circuits. There are also some rare cases of power amps with self-biasing circuitry. But in this guide, we’ll focus on those that require biasing.

Bias can roughly be described as running water through a tap. It can either be a steady stream, a slow stream, or an unbearably strong stream. Ultimately, the proper bias will keep the tubes operating properly and at the desired temperature. With the right bias, your amp’s tubes will not only produce a better tone but will have a longer life.

So we have three possible outcomes in this:

  • Over-biasing: If over-biased, there won’t be enough voltage to run the tubes properly. As a result, your tubes are colder and the tone is much “thinner.” However, your tubes will last longer this way.
  • Under-biasing: If under-biased, tubes will run too hot. The tone will be much more saturated, although the tube life is significantly shortened. Additionally, with significant under-bias, you’re risking damage to other components as well. If you need an under-biased setting for a saturated tone, make sure not to overdo it.
  • Optimum: When biased properly, tubes will work at their optimum, bringing the best balance of life and tone.

Explaining the Tubes

A vacuum tube in a guitar amp (or any other device) serves to help amplify the signal. Ultimately, it impacts the tone and makes tube amps sound the way they do. We can essentially say that vacuum tubes consist of these four main components:

  • Cathode
  • Heater
  • Grid
  • Anode (or “plate”)

So essentially, the heater heats up the negatively charged cathode, making it emit electrons. Then these electrons flow through the vacuum towards the negatively charged anode. In between these two components is the grid which controls the electron flow, ensuring proper operation of tubes.

It’s important to note that the grid controls the electron flow both when you’re playing and when you’re not playing. And the first process impacts the second.

So why did we mention these grids? Well, both the grid and the bias voltage are part of the voltage control process. Ultimately, it all impacts your amp’s tone.

Why Is Tube Amp Bias Important?

In almost all cases, you’ll have to get your amp biased when you replace the old power amp tubes. Additionally, I’d also recommend that you bias a new tube amp that you bought. Essentially, the optimum bias provides a safer operation and, objectively, a better tone. You don’t want to shorten the lifespan of your tubes, damage your amp, or have a weak tone.

You might also wonder if it’s necessary at all. Well, you can technically go without biasing, but you’re risking meeting these aforementioned problems. So it’s highly advisable that you do it.

Should I Do It Evert Time I Replace the Tubes?

While we’re at it, biasing is something that you should do every time you replace the tubes. You might wonder, however, why this is required. After all, the amp is set up for, let’s say EL34 power tubes. So you put a new set of EL34s. Should it be biased then?

Absolutely. Biasing is recommended after every tube replacement, even if it’s the same model and the same brand and manufacturer. The problem is that every tube is a little different. And you’ll need that extra fine-tuning to make things work within the optimum limits.

How Much Does It Cost to Get Amps Biased?

Now we get to the main question. The cost of biasing can usually be anywhere between $25 and $100. A complete bias, if you’re doing it the first time or if you’ve just bought a new amp, would be more expensive. Rebiasing, on the other hand, should be a bit cheaper.

Additionally, it also depends on the amp’s output power, which directly correlates to the number of tubes in the power amp. So if you’re taking your 100 or 150-watt head to get biased, you’ll need to be ready to pay more. If you have a smaller amp with one or two power tubes, it’ll be a cheaper ordeal.

However, in the end, it all depends on the particular tech that you’re taking your amp to. If the tech is the only one around, they’ll likely charge more.

Can I Bias and Re-Bias My Amp By Myself?

If you’re not an experienced tech and have no experience with electronics, it’s absolutely out of the question that you do it yourself. Even when it comes to basic voltage measurements, I’d highly advise you to keep away from that. I’ve been playing tube amps for quite some time and I’ve always taken them to a professional.

The problem here is that a tube amplifier can be pretty dangerous. Even if it’s turned off and not plugged in, there might be some voltage inside, strong enough to cause trouble. Additionally, it’s a delicate procedure, and if you don’t know what you’re doing, it’s better to take it to a professional instead.

Sure, you might find plenty of YouTube tutorials that explain how it’s done. But don’t do it on your own if you’re not a professional electrician. There are serious potential hazards and it’s simply not worth it.

Self-Bias Circuits

There are also tube amplifiers with self-biasing circuits in their power amp sections. But first, let’s see the main division, the three types of tube amps according to biasing methods:

  • Adjustable fixed bias
  • Non-adjustable fixed bias
  • Cathode bias

Adjustable fixed bias (a bit of a weird name, though) refers to amps where bias can easily be adjusted using special controls. Non-adjustable refers to amps that have non-adjustable factory-set bias. These can only be adjusted by tweaking the circuitry itself.

Finally, we have the cathode bias. These are most commonly referred to as the “self-biasing” amps. These are not that common, but they’re present with some modern amps. When you’re doing the replacement, just use a full set of matching tubes, and you’re all set. These are most often low-wattage amps with less headroom. This means that their tone distorts more easily, even in a clean setting. Additionally, these amps usually tend to sound smoother and “looser.”

How Often Should You Get Your Tube Amps Biased?

How often you should bias your amp depends on how much you play them. If you’re playing it daily, or almost every day, then you should go and get it checked once every 3 to 6 months. It’s always a good idea to listen to how your amps act. If their tone changes and if they become noisy, it’s probably time to re-tube and re-bias them.

Are Tube Amps Outdated?

With all this said, you’re probably wondering whether tube amps are even worth it. After all, this is an outdated technology, right? Well, it may be, but plenty of guitarists are still very keen on how they sound. They’re most certainly way more capable of delivering dynamically responsive tones compared to solid-state amps.

However, we have so many advanced digital amp modelers today. And, additionally, they require no additional costs like biasing. Sure, they might be a bit pricy, but in the end, they don’t require maintenance costs. There are just some firmware updates, maybe additional presets that you can purchase, and that’s it.

At the end of the day, the choice is up to you. Try as many amps and modelers as you can and determine what suits your playing style. After all, there are as many styles as there are guitar players. It’s up to you to figure it out and find it in you.