How To Identify Types of Vacuum Tubes

Pairing a great tube with a great amplifier is the key recipe in anyone’s audio tone. Do different tubes really make much of a difference in your sound?  How can you identify what tubes go with which amp, with all the different types of vacuum tubes out there?  What’s the difference between an EL34 and a 6L6?  We’ve put together this reference guide to introduce you to some of the basic differences between some of the classic tubes and their classic sounds.

 

 

Different Types of Vacuum Tubes

6DJ8

Designed for TV tuners and industrial equipment, the 6DJ8 instead became popular in hi-fi amplifiers and are now relatively hard to come by.  They are low noise, low volume and better for low gain buffer applications.

5751

The 5751 is a great tube for shaping your tone, giving you a higher level of control over the warmth of your high end and clarity of your midrange.  For more gain, switch to a 12AX7.

12AX7

12AX7 tubes are very common in guitar tube amps from Fender and Vox among others (I like the Monoprice tube amp myself).  The cleans have more clarity and gain, and overdrive modes have more crunch. Swap your tubes out for these for tone transformation.

6SL7

With dual hi-mu triodes, the 6SL7 is a good alternative to the 12AX7.  This tube has very clean gain with a sharp single note definition not found elsewhere.

KT88

High power and low distortion make the KT88 more popular with hi-fi amps than guitar amps.  They are regularly used to replace 6550 tubes when seeking a cleaner tone. It’s also one of the largest tubes in its class and capable of handling higher voltages.

6L6

You know this tube whether you knew it or not.  The 6L6 is THE sound of rock and roll – the Fender amp sound, with a low to medium gain clip great for rhythm.  The 6L6 has also found widespread popularity in many other applications as well.

6v6

The 6V6 is the sound of the Fender Tweed amp, with a reduced low end compared to the 6L6.  It also has the longest active production lifetime of any other electronic component, having been in continuous production for over 80 years!

2A3

The 2A3 has a wide dynamic range like the 6550, but with a lower power and lower volume, and also an impressible low noise floor, making it better for use in preamps.

EL34

The EL34 is the classic sound of the British Invasion, finding common use in Marshall amps, Orange amps, and many others.  Their memorable sound is characterized by greater distortion at lower power than other octal tubes.

EL84

Upon release, the EL84 were a better priced alternative to the EL34 or 6L6 tubes.  The creamy overdrive and great volume of the EL84 can you from a blues twang to a rock edge.

KT66

This tube has great crunch when overdriven, but more bite than the similar ET34.  The KT in KT66 stands for “kinkless tetrode”, a performance improvement over other tubes available at the time.

6550

One of the most commonly used tubes, the 6550 is versatile in both guitar and stereo amps and is known for its signature wide dynamics & full bodies tone.

If you’re a musician looking to dial in your perfect tone, check out our list of the best 5-watt tube amps!

If you’re an audiophile looking for a great improvement to your stereo system, check out our list of the best tube headphone amps!