It’s Tube Time
Welcome back to Andy’s Corner! Last week, we took a look at some small ways that you can tweak and improve your tone. This week we’re looking under the hood of your tube amp to take an overview of power tubes and how the various vacuum tubes that are used affect your tone.
The Tiny Backstory
The quick history: in the late 1800s, scientists were experimenting with gas-discharge and electrical-discharge tubes. Edison and Tesla are among some notable scientists who experimented with tube technology and helped lay the groundwork for the modern vacuum tube. The tube amp as we know it was popularized in the 30s and as we all know—guitarists took those things and ran with them, discovering that by pushing the tubes they could get a crazy new tone: overdrive! Rock and roll is born.
The Four Tube Groups
When you do the requisite research, you’ll notice that most of the popular tube amps on the market today use a few common tube types (each associated with a certain tone). The typical tubes in use today are:
EL84: This tube is most associated with the “Vox chime.” It is used predominantly in Class A tube amps—where the amp runs all hot, all the time. The EL84 has sparkling highs and a crunchy midrange that responds very well to being pushed—just like in an AC30.
EL34: Marshall Stack. That is all. The EL34 is the wall-of-rock sound that we all grew up with—whether you grew up with Plexis or JCM800s, you grew up with EL34s. They are known for their ability to produce distortion at lower power, making them desirable and essential for amps that are chasing that full stack sound. Some players are experimenting with swapping out EL34s for KT77s or 6CA7s, often reporting that the 6CA7s offer a good cross between the EL34 and 6L6 tones.
6L6: The big, clean tone that Fender is known for comes from the 6L6. This tube is what gives the Twin and the Super Reverb their power, allowing rich full bass and sparkling highs. The tone of this tube is typically considered an “American” voiced tone, frequently used in Fender-styled combos and many more-modern American amps. KT66s are sometimes used as a replacement for the 6L6 with many players considering them to be the smoother overdrive of the two.
6V6: The 6V6 is the old timer of the group—known for providing that sweet tweed tone to smaller vintage combo amps from the 50s and 60s, such as the Fender Champ and the old Gibson GA-40. 6V6s fell out of favor (to be honest, they fell out of manufacturing) for many years and are currently experiencing a resurgence due being available on the market again.
Changing your tubes can have a drastic affect on your tone. Even simply changing brands of tube can produce a stunning result in your amp. Unfortunately, the only way to know how a brand will sound in your amp is to: put those tubes in your amp. However, the good news is that most of us guitarists are die-hard tinkerers and you’ll probably have a lot of fun experimenting. You typically should not simply swap power tubes in and out—as most tubes are going to have unique or incompatible circuit/voltage/bias specs. We recommend always taking your amp to a pro, unless you are yourself a pro—manufacturing and quality-control variations across brands mean it’s safer for you and your amp to have a tech swap out the tubes and perform any necessary tweaking/biasing/re-wiring necessary to make the jump. If you’re simply replacing a tube with one of the same variety, we recommend handling the tube with a clean, dry cloth; finger oil residue on the tube can linger and create a hotspot, almost ensuring that tube will blow faster than others.
As with any aspect of guitarland, your mileage may vary. There are a ton of manufacturers manufacturing a ton of different types of tubes that will yield: a TON of different tones in your amp. With plenty of resources available online, you can start to hone in on a few choices that might yield you an improvement in your stock tone. You’ll need to actually make the leap and get the tubes installed to know for sure, but when you arrive at that glorious moment when you hit a power chord and the sound you’ve been dreaming of comes right back at you—it’ll all be worth it.
One of the best resources online is YOU—if you’ve got anything to share about swapping tubes out, let us know in the comments and let’s discuss. Thanks for reading and see you next week!