Despite the complicated circuit diagrams found glued in their cabinets, tube amps are relatively simple creatures. They take an electrical signal, amplify it and turn it into sound via vibrating membranes (speakers). There are plenty of links in that chain that can affect your sound, but the biggest two are probably the type of speakers and the type of tubes being used. We’ll save speakers for another day and focus this article on the characteristic tones produced by four types of power tubes.
Let’s just get this out of the way: this is not a technical or historical article. These are just my opinions from playing a lot of amps with a lot of different tube types. I’ll try to describe here what I feel defines the response of each type of power tube in terms of tonality. The aim is to help you find the right amp for the tone you’re after without taking up too much of your time. This is how I hear it, but feel free to disagree in the comments thread. After all, difference of opinion and interpretation is part of what makes music great.
Overall, this is my personal favorite type of tube, typically found in amps with less than 30 watts. Fender is well-known for using the 6V6, and you’ll find it most often where designers are chasing a low-powered “American” clean tone. What’s great about 6V6 amps is that they are very musical, especially for clean tones and distorted lead tones.
When playing lead, the tone feels more complex and really starts to sing. On the flip side, many players feel 6V6 amps are too loose for tight rhythm playing, especially with higher gain and lower frequencies. They can get a bit muddy when pushed and don’t track quick or intricate playing on the lower strings very well. The more you push a 6V6 amp, the more you’ll notice this undefined low end. Several amps equipped with 6V6s are renown for their clean tones, including the original Fender Deluxe Reverb, the original Fender Princeton and more recently the Fuchs Blackjack 21.
The EL84 is a very chimey and tight beast. Also usually found in amps less than 30 watts, these are more common in British designs. The EL84 can bite when pushed, so in some amp designs they might feel stiff or harsh, but they can also hold distorted tones together better than a 6V6 amp. If you plan on playing higher gain or pushing the amp to its limits when playing rhythm, you may prefer an EL84 amp.
A friend of mine made me a Trainwreck clone that uses four EL84s and it sounds incredible. You’ll also find these in Vox AC15s and AC30s, as well as smaller Marshall amps like the current DSL combo series.
The “other American tube.” These are found in most amps over 30 watts, though the power rating of the amp can vary quite a bit. 6L6 amps make a good canvas for preamps and pedals, so you’ll see a wide variety of 50 to 100-watt amps using these in the power section. From sparkly cleans to warm overdrive and modern high-gain tones, 6L6 amps can have a bigger low end without losing clarity. They also impart a bit of a mid-range scoop which many players appreciate.
I have a ‘64 Fender Tremolux with 6L6s that has the most gorgeous clean tones. This uncolored starting point seems to bring the best out of every pedal I run into it.
Commonly referred to as the “British” sound, amps with EL34s in them are often assumed to have some sort of Marshall flavor. They are often viewed as the counterpart to the 6L6 and are usually found in amps over 30 watts. While not a one-trick-pony by any means (I have a Rivera with EL34s and it can do a pretty convincing Blackface), EL34 amps are generally assumed to have that Marshall mid-rangy bark. For that reason, EL34 amps are my favorite for distorted guitar tones of the classic rock variety. That Rivera is amazing, and my Marshall JMP is a 50-watt box of pure attitude.
It’s worth noting that tube choice is just one component of a larger overall design, so much of the tonal variance comes from the general circuit and not just the tubes themselves. As you play more and amps with different tubes, you’ll start to hear commonalities and see where these lines can be drawn. As for me, I’ve learned to appreciate the difference between each type as a great excuse to “need” a new amp…