As a lover of sound, I’m guilty of tunnel vision when it comes to guitar and bass amplifiers, often emitting a low groan when I arrive at a stage with backline gear not to my liking. It’s discriminatory and, in fact, my judgmental eyeballs do this with almost every object on the planet.
So, I decided it’s time to make an attempt to break out of my comfort zone and preconceptions, and let my ears decide what’s best for a given stage or studio situation—while giving my biased peepers a rest. To help me get a fresh perspective and possibly reinvent my concept of what sounds good, I enlisted two colleagues, Jamie Stillman and Ben Vehorn of EarthQuaker Devices, to shed a little light on my otherwise dark and singular path. I also work at EarthQuaker, and I’m a pedal and amp builder. Jamie is the genius behind some of the coolest effect pedals out there, while Ben has worked in studios for years, earning a unique perspective on the audio-capture end. I also enlisted a half-dozen intriguing examples of vintage transistor titans and tiny terrors. Our goal: to open my heart and mind—and maybe yours, too—to some great sounding solid-state amps.
Enter the Wayback Machine
Before we get cracking, let’s take a trip back through time to get some footing in amplifier topologies. In 1906, Lee de Forest—the self-described “Father of Radio”—improved the basic valve diode by including a separate, third electrode, thereby inventing the main building block of early tube amplification. Fifteen or so years later, this starts getting called the “triode,” sensibly enough. Sounds science-y and cool, right? And as we approach the middle of the 20th century, the pentode (with five working elements) starts to show up and becomes a mainstay in the world of vacuum tubes. These new devices were perfect for the requirements of wartime, with lower manufacturing costs and greater versatility. They were also great for amps, because with each new element in the tube, bandwidth, tone, and feel characteristics improved.
Then along came transistors. The first patent for a transistor was issued in 1925, but things began to get serious in ’47, when Bell Labs in New Jersey started experimenting with germanium crystals made in a lab, and discovered their ability to create output power greater than their input. That led to the first practical transistors for mass-production, based on those lab-cultivated crystals. (Yep, that’s right. Fuzztone was born in a petri dish!)
Bell Labs was quick to slap a patent on this new wonder, and the first transistor radio appeared in 1954 with germanium diodes—the first solid-state semiconductors on the scene—inside. Later, as with tubes, a third electrode was added to the mix, and the germanium transistor you know from “Purple Haze” was born.
One commonly known limitation of germanium transistors is temperature instability. They get hot and start performing shoddily with regards to linearity and gain. To combat this phenomenon inherent to germanium, silicon was used for its abundance and better performance characteristics under metaphorical fire. Silicon is also the second-most-copious element on Earth, next to oxygen. And it conducts electricity excellently, and that only gets better with heat. Silicon transistors operate by passing electrons through a solid material—silicon crystals—which act as a semiconductor. Sometimes silicon transistors are referred to affectionately as “sand-state” because sand is composed of silicon. Tubes are sometimes referred to as “hollow-state” because they are either gas-filled or—like amp tubes—have a vacuum inside. This open space is where all the aforementioned elements of the tube do their magic.
Once silicon became the new champion of transistors, solid-state amplifiers were off and running. In fact, solid-state became the go-to status for all kinds of products. Another appealing advantage of solid-state technology is that it requires much lower operating voltages than high-voltage, high-impedance tubes. The low-impedance signals typically spit out by transistors are also great for driving low-impedance speakers, while tubes need an output transformer to take the tubes’ high-impedance output and match the signal with speakers.
Since solid-state amps don’t need an output transformer, they have a much lower weight than tube amps. That’s a win for maker and end-user alike. The power transformer is also slimmed down. Since transistors operate at much lower voltages, they make it easy for lightweight power transformers to supply the DC voltage to fire up an amp.
Think of it this way: The wall at my house puts out 117 volts AC. To feed the tubes, I gotta step that voltage up inside the amp at least a couple of times to get what I need. That takes a big power transformer. Then there’s the heater winding of the tube amp power transformer, adding yet more weight. But a solid-state amp is taking the 117V AC from my wall and stepping it down to around 50V DC after rectification. This less taxing exchange typically makes the power transformer smaller in solid-state amps. So, the less iron an amp has inside, the easier it can be lifted.
This simpler construction also means less can go wrong. And solid-state amps also have less of a shock hazard. Tube amp operating voltages are significantly higher than what exits in the wall, and they have high levels of DC voltage, which can really zap you and keep zapping you, since there is no rise and fall through the zero crossing, which happens with the AC voltage that powers solid-state designs.
That Other Tube Bias
So cool—those are the basics. What about the differences in sound?
Tube amps are said to be “warmer” and solid-state (aka transistor) amps are typically called “flatter.” When I ask most of my pals about the sonic differences between tube and solid-state amps, that’s the consensus. But why have these generalizations become common?
I think it stems from each device’s saturation characteristics. Tubes are slow and unpredictably predictable—the way a tube distorts and produces harmonic non-linearity, the way it interacts with other tubes later in the circuitry. Transistors, on the other hand, take what you give them and barely wince. They do a tip-top job of not imparting additional color to the sound going through them. They are also much faster devices than tubes, which translates to a more immediate sound and feel. This isn’t to say that tubes and transistors can’t sound just like one another, because they totally can and often do! If you give musicians a blind listening test of different tube and transistor audio circuits, there’s gonna be some crossover in the answers. Well, at least in my own.
But generally speaking, I’m with the crowd on the difference-in-sound debate. If I want a pushed guitar sound that only gets more unhinged as I crank the amp up, it’s tubes. If I want a balanced, even sound for my new guitar no matter what venue I’m in and where the volume knob is set, that’s solid-state.
It’s not really this cut and dry. When considering your own options, use your ears to find your sound—even if it’s just for today. You can always change amps again tomorrow.
So, armed with all that, let’s bring one of our experts, Jamie Stillman, into the conversation.