The debate raged from the 1950s through the ’80s and into the early ’90s: tube amplifiers verses solid-state amps. These days, the clear winner in the working musician’s marketplace is tube amps. Even high-priced emulating amps rely on tubes for at least a portion of their tone sculpting — the preamp. And among boutique amp manufacturers it is clear that the tube is king.
Why is tube driven sound so important to so many guitar players? Here’s the lowdown.
In the 1940s when guitar amplifiers became widely available all amps were tube amps. So when you hear Muddy Waters’ incredibly rich and filthy tone on his 1948 Chess recording of “I Can’t Be Satisfied,” that’s a first generation tube amp — low wattage pushed to the glorious maximum. In the 1950s transistors became available and yielded the solid-state amp — and the debate mentioned above began.
Generally speaking, tubes have a softer attack. Try hitting a barre chord while plugged into a solid-state amp and then try it with a tube amp. The difference is audible. The solid-state amp will have a faster response and a sharper edged tone, which is perfect if that’s what’s desired. Tubes, on the other hand, give notes pumped through amps a softer edge and tend to enhance their bass frequencies, which translates to the ears of most experienced guitar players as a more desirable sound.
Tubes also have natural distortion, verses the clean and accurate reproductive qualities of solid-state amps. On paper that seems like a negative, but listening to that early Waters recording, its obvious that’s where the juice is for many of us. The more electrical energy that’s channeled into tubes, the hotter and more distorted they become. Some solid-state amps and all modeling amps compensate for this with circuit design. How well they succeed is a matter of personal taste. For my money, I am very happy with the low-volume tones generated by some of the least expensive modeling amps on the market, which retail for about $100. They can yield excellent results for recording and are superb for practicing in an apartment.
In engineering circles, what exactly makes a tube amp sound warmer is also debatable. Some say it’s due to clipping — a distortion of waveforms that occurs when an amp is overdriven. Others say it’s the harmonic distortion that tubes produce. Then there’s preamp tube and power tubes, which both color your guitar’s sound in different ways.
Weighing all of that is confusing. And then there’s the issue of selecting an amp on the basis of the tubes it comes with, or choosing replacement tubes for an amplifier. To help with the latter, here’s a guide to the basic types of tubes available on the market and their ideal applications:
• Preamp tubes: These tubes are the easiest to replace. It’s just a matter of plug and play. They’re also an important part of coloring guitar tones. Some manufacturers, like Mesa-Boogie, make their own tubes, but GE, RCA, Sovtek and several others are also in the game.
Tubes differ by the materials and elements used in their construction, and are identified by a combination of letters and numbers. So when you stride into a guitar shop, be prepared to order by that combination. Generally, if you’re looking for tubes for an acoustic guitar amp, consider 12AY7, 5751 and 12AT7 tubes. For blues and ’60s and ’70s rock tones, 12AX7s are the most commonly used. Punk, grunge and old-school metal players tend to like 12AX7s and 12AX67s. And for extreme music tones, 12AX7LPS, 12AX7s and ECC83S are frequent fliers. Overall, tubes within the AX family will provide a nice overdriven sound.
Of course there are vintage tube specialists and high-end tubes makers in the marketplace. If you’ve got the time and interest, speak with your local music dealer about what makes the best sense for your gear and your style.
• Power tubes: After the preamp tubes do their tone sculpting, it’s the business of the power tubes to get that sound out into the world. EL84s are a good foundational power tube. They do a solid job of pushing out what goes into them with minimal tone coloring. EL34s tend to have a little more distortion, making them blues and classic rock favorites. 6L6 tubes also fall into that category, but produce a warmer bottom. And KT88s are good for all applications, but especially sweet for bass amps.
Preamp tubes can be switched out without a care, but power tubes are trickier. If you’re switching to a new type of power tube you should have your amp re-biased, so it is set to run with those tubes as efficiently as possible. It’s a simple job that any decent amp tech will be able to do a minimal cost.