Are Tube Amps Supposed to Glow?

If you find yourself asking, “Are tube amps supposed to glow?” it’s probably because you have just discovered glowing tubes within your amplifier. This article will help to clear up whether or not that’s normal, and what you should be looking out for.

Gemtune MC-10T

Is it normal for a tube to glow orange?

Although the specific design of your amplifier will affect how well you can see your tubes while your amp is powered on, most people will notice a slight orange or yellow-gold glow in their amp’s tubes as they play. This is normal and, as the fillament heats up, you should expect to see some orangey glow coming from your tubes.

However, problems can arise if it’s not the tubes that are glowing orange, but rather the metal plate of the tube that is glowing orange or red. Although the tubes themselves will be orange as they heat up, the plates should remain a dark color. If you see the plates turning orange or red, you might have a problem on your hands.


Is it normal for a tube to glow blue?

If you’re playing your amp and you have noticed that some of the tubes are glowing blue, you might start to fear that you have a defective tube or even a defective amp all together. Not to fear: Tubes often glow blue, and it is by no means an indication that the tube is bad, or about to go bad. In fact, tubes glow blue on a normal basis and it should not raise alarm in any way whatsoever.

The blue glow that you are witnessing is just a side effect of the power tube. It’s a fluorescent glow in the blue spectrum and the tube is actually completely fine. The blue glowing tube has a good vacuum within it, which is good. This is what’s causing the phenomenon to occur. You should not notice any sort of negative effect on the performance of your amp or its tone.


Is it normal for a tube’s metal plate to glow red?

While a blue glowing tube is entirely normal to witness in a well-functioning tube amp, there’s another type of glow that you should be watching out for. Have you been playing your amp recently and noticed that there is a red glow? That might be a bad sign.

If you are seeing a red glow on one or more of the metal plates on one of your amp’s tubes, that is not something that should be ignored! If one of your metal plates is glowing red, you should immediately power off the amp. A red glowing metal plate is a sign of a problem, and continuing to use your amp can result in damage.

Although a blue glow indicates a tube is functioning normally, a red glowing metal plate indicates the opposite. A red glow within one of your tubes’ metal plates indicates that the tube is overheating, hence why it is glowing red hot! It may be fun to look at, but it’s not a good sign at all.

Your tubes’ metal plates are glowing red hot because they are overheating. Likely, this is because your amp’s tube bias has been incorrectly set. However, there could be another reason that is causing the tube to overheat. In either case, you should turn the amp off right away if you notice a tube’s metal plate glowing red. If you leave the amp on or continue to play it, the overheating tube can damage your amplifier.

Instead of continuing to play your amp, when you see a metal plate that’s glowing red inside of your amplifier, you should turn it off and have your amp checked by a technician prior to your next use. If the problem had to do with an incorrect tube bias, the right technician will be able to get that fixed for you without much fuss. Of course, if there is another underlying issue, it may take a bit more effort to remedy.


Noticed a strange glow?

If your tube amp is glowing on the inside and you don’t think it’s normal, the best thing to do is power down your amp, unplug it, and ask a technician to come and have a look at it. That’s the best way to prevent damage to your amp, but don’t go opening it up on your own. Tube amps are extremely high voltage and they are truly complex.

Get help if you find yourself asking questions like, are tube amps supposed to glow? When it doubt, always call in a professional for assistance and you’ll be back to playing soon enough.


For more info about glowing tube amps, here are some resources I hope you find helpful: