Tube Amps vs. Solid State Amps
Ever since solid state amplifiers emerged in the 1960's the debate has raged over which is better for bass, tube amps or solid state amps?
For us bass players the choice isn't quite as volatile as it is for guitar players, many of whom would rather drink poison than play through a solid state amp. Still, there are those bassists that swear by that natural warm, fat tone that a tube amp delivers.
So the question is, what's the difference between them and what's best for you? Oh yeah....there's also a third option.
The vacuum tube amplifier or valve amp as it's sometimes called was for many years the only way an amp was powered. At it's most basic it is a piece of audio equipment that increases the amplitude of a signal using vacuum tubes, or valves.
Amplitude is normally measured in peak-to-peak amplitude, which is the amount of change between the highest part of a wave, the peak, and the lowest part of a wave, the trough. This is the aspect of a signal that the amplifier increases. Tube amps use a "push-pull" system also called a class AB output section that splits the audio signal at the tubes and then rejoins them at the output transformer for greater efficiency and longer tube life. This also contributes to the tube amps unique tone.
Amplifiers based on vacuum tubes, or valves, were introduced in the early part of the 1900's and dominated the market up through the 1970's. When transistors became popular due to their lower cost, lighter weight and higher reliability, tube amps saw a huge decline and the solid state amplifier took over as the favorite choice for most bass players. The 1980's in particular saw an enormous increase in solid state bass amplification and stayed that way until the early 1990's when grunge emerged and the shift back to all things vintage including the tube amp sound started.
Virtually every style of music employed tube amps prior to the 1970's, from Jazz and Rock, to Pop and Funk. The warm fuzz of 60's psychedelic rock and the fat bass tones of 70's funk is an unmistakable product of those circuits.
Most musicians and studio technicians who use tube amplifiers do so because they love the warm, natural sound produced by tubes as opposed to solid state circuits, which can sound artifical or sterile to some. A tube amp will have more pleasing harmonic ovetones than a solid state amp due to it's smoother transition into clipping ranges (overdrive). Tube amps also will sound louder than a solid state amp set at the same volume. Although technically solid state circuits have higher fidelity than tube circuits, lovers of tube amps swear that there is a huge difference in the quality of sound produced by all tube equipment. The tone that they produce is pretty much the only benefit, but it is obviously an important one when it comes to music. Oh, and there's also that really cool tube glow you get from a warm valve.
Tube amps are generally much heavier, much less reliable and much more expensive than their solid state counterparts. Tubes can break or blow out, and they tend to get very hot. Companies today that produce new tubes are often only found in Asia and Eastern Europe, and sound quality can vary from tube to tube. Although this last point is a benefit for some people who enjoy that randomness from their sound as something more natural to work with. Then there are others who will search everywhere and pay heavily for new old stock American and British tubes.
Solid State Amps
The solid state amplifier has been around since the 1960's. They're called solid state because the electricity moves through solid material rather than a vacuum like in tube amps. The amp uses transistors instead of tubes to amplify signals.
In the early days these new transistor amplifiers were much maligned among bass players. The main problem was that unlike tube powered amps a solid state amp will cut off the signal at it's peak rather than pull it back like a tube amp will. This created an unpleasant distortion and somewhat dry, sterile sound. In recent years however the solid state amp has become much more musical sounding due to newer technology and a better understanding of how to replicate tube circuits within a solid state design.
Using solid state amps is much less controversial in the bass community than it is with guitar world. With bass players the choice is more about the sound they're after rather than the actual quality of the signal. Many bassists prefer the clean uncolored tone of the solid state sound, not to mention the greater power and lighter weight. The reality is that solid state amps are here to stay and are getting better every year. While some bassists will always prefer the tube amp sound, the solid state amp is still king in the marketplace.
Solid state amplifiers are lighter and generally less expensive than tube amps. They are also much more reliable and require very little maintenance. A solid state amp can produce far more output (watts) than a tube amp of similar size. They also offer faster transient response times and a clean, transparent sound favored by some bassists and producers. Many solid state amps have more tone options than a tube amp, especially on the higher end models.
If you're after the old school tone of a tube amp, a solid state amp just won't do, and a tube amp is what you need. While there are many convincing solid state tube simulators on the market, for many bassists nothing can replace the warmth and pleasing natural distortion of a real tube amp. Solid state amps will clip more abruptly than tubes which can sound harsh to the ears. Even the highest end solid state amps will not give you that soft, warm compression and overdrive that only vacuum tubes can produce.
In the last decade or so there has been another amp option, the hybrid amp. It's basically an audio device that uses both transistors and vacuum tubes to amplify a signal. Hybrid bass amps have become extremely popular in recent years mainly because they combine solid state reliability with that warm tube sound.
Most hybrid bass amps use a solid state power amp stage with a tube pre-amp section feeding it. This design allows for more power without the need for an output transformer like in a classic all tube powered amp. Essentially the solid state power section does the heavy lifting, dramatically boosting the signal and driving the speaker. The pre-amp section usually contains only one or two tubes (some have more) that basically color the tone of the signal, giving more warmth and tube flavor to the sound.
Most hybrid amps will never sound as warm and fat as an all tube amp, but the hybrid is the perfect compromise for those bass players who want a real tube sound without all the heavy lifting and maintenance than comes with an all tube amplifier. Hybrids usually cost less and are easier to maintain than an all tube bass amp. For most situations a hybrid amp will work well because by using the settings you can achieve either a clean solid state sound or a warm tube sound. This is especially useful to bass players that play many different styles and need as many tone options in their amp as possible.
Hybrid amps tend to be more expensive than solid state amps of the same power rating. Because hybrid amps have pre-amp tubes they will require more maintenance than solid state amps and will also be more likely to break down. Hybrid amps are usually a little heavier than a solid state amp of similar size due to the extra components in the tube section.
The bottom line is that you have to choose what's right for you, and not just because your favorite bass player uses a particular amp. In fact many bassists have both tube and solid state amps for different situations. I personally prefer the all tube amp sound but usually play through a solid state amp for convenience. Then there's also a fourth option, the digital amplifier...but I won't go into that now.