Tube Amps vs. Solid State: What's The Difference?

If you've ever been amp shopping, I'm sure you've heard the term "tube amp" tossed around quite a bit.  I remember looking around for a new amp when I was in high school and wondering why some amps were louder than others with the same wattage rating.  I was also confused about why some amps had standby switches while others didn't.  A salesperson at my local guitar shop let me know that these differences had to do with whether an amp had "tubes" or not.  To me, the obvious next question was, well... which is better?  The prevailing ideology from most guitarists has always been that tube amps are more desirable than those without tubes (referred to as "solid state amps"), but there are many guitarists who choose solid state amps for one reason or another.  In order to understand which is right for you, it is important to understand what tubes are and what they do to an amp, and what the differences between tube amps and solid state amps really are.

What Is A Tube?

As recently as the 1960's, vacuum tubes like the ones found in many modern guitar amplifiers were a common electrical component in just about every electrical circuit.  Telephones, tv sets, radios and just about everything else you can think of all used tube technology.  However, in 1947 the first transistor was developed, and this would eventually eliminate the need for tubes in many if not all of these devices.  The end of our dependence on vacuum tubes is a factor in the reduction of size of many household devices.  Perhaps you are old enough to remember how thick televisions were they still had tubes in the back.  Today, televisions are so thin and light we can mount a sixty five inch screen to our walls without thinking twice about it. 

There are a few different types of tubes, but the kind used inside your guitar amp is called a "triode".  A triode is simply a cathode and an anode placed inside of a glass vacuum at opposite ends.  The cathode releases electrons (negatively charged) when it is heated by a filament that is also inside the tube that has current flowing through it.  Since the anode has a positive charge, the negatively charged electrons are drawn to the anode, and can move freely because the tube is a vacuum.  A control grid (like a plate with holes that allow electrons to pass) exists between the cathode and the anode, and by controlling the voltage on the control grid it is possible to increase (amplify) the current that reaches the anode.  By placing a negative voltage on the control grid, the negatively charged electrons will be repelled from the plate and a reduced current will reach the anode.  By placing a positive charge on the control grid, more electrons will be drawn to the anode, amplifying the current that reaches the anode from the cathode. 

To illustrate:
Triode Tube Diagram 

If you're interested in learning more about how tubes work, check out this site which covers some of the history and the science, or this one that covers it from the perspective of a guitarist.  

The Pros of Tube Amps

Many of our favourite guitarists like Jimmy Page, Hendrix, Stevie Ray Vaughan and George Harrison used tube amps.  For some people, this alone is compelling enough to sway your decision making towards tube amps.  However despite the fact that tube amps were the first available on the commercial market and therefore more easily accessible during the height of many of our favourite guitarists' careers, there is a reason why so many of them decided on tube amps instead of using solid state.  Tube amps, when turned up real loud have a tendency to overdrive in a very musical way.  The practice of turning your amp up very loud and then controlling the level of gain with the volume on your guitar is much more effective when done using a tube amp.  This is because as the tube amp sees more or less signal from the guitar, the tone will change more drastically than with a solid state amp.  This makes tube amps far more dynamic and malleable than solid state amps.  

Additionally, the vast majority of overdrive pedals on the market today sound best when used in front of a tube amp.  This is because a great deal of overdrive pedals are built to be as tonally transparent as possible.  That is to say that these pedals are intended to push your amp and coax from it the sounds that are created when the amp is cranked, but at a bit of a lower volume.  A cranked tube amp sounds fantastic.  A cranked solid state amp just sounds like a louder version of a quiet solid state amp.  

Finally, tubes tend to compress your signal naturally, something that lots of guitarists really love.  Tubes can provide a little bit of sustain and compression in a way that doesn't squash your tone like so many compressor pedals tend to do.

The Cons of Tube Amps

All of the negative aspects of owning a tube amp have to do with pragmatic concerns.  For instance, tube amps tend to be more expensive than solid state amps.  That said, in more modern times many of the digital solid state amps on the market are beginning to challenge that norm.  Systems such as the Kemper or the Helix by Line 6 or even Axe FX can be more expensive than a decent tube amp.  

Tube amps are often heavier than solid state amps.  This can be difficult for gigging musicians who often need to take their equipment up a flight of stairs to get to the stage, or for anyone who has ever lived in an apartment.  

Another con is that tube amps are fragile.  Glass tubes are liable to shatter if the amp is dropped or carelessly handled.  Tubes also need to be replaced after a certain amount of regular use, and replacing them involves a process known as "biasing" the tubes which can be challenging to anybody who has little experience with working on electronics.  Tubes can also break in the middle of a gig (although its rare if everything has been set up correctly).  For this reason, anyone who owns a tube amp must eventually incur the cost of replacing tubes.  

There are lots of brands to choose from, but I usually buy JJ Electronics tubes because I've found them to be very reliable and long lasting.  When you're replacing your tubes, you need to make sure that you purchase the correct model of tube for your amplifier.  The three above models are all 12AX7 tubes, which is an extremely common preamp tube.  You need to check and make sure you know how many pre amp tubes you need, and double check that they are 12AX7's.  Preamp tubes usually do not need to be changed as often as power tubes.

EL84 power amp tubes are a common model, known for their use in Vox AC30 and AC15 models, as well as the Fender Blues Jr.  

EL34 power amp tubes are often associated with the "British" sound.  These model of power tubes can be found in Marshall amps such as the JCM800 and JCM900 as well as other British amps by Orange and Hiwatt. 

6V6 power tubes have been often associated with the "American" sound, and can be found in many popular Fender amp models including the Deluxe Reverb and the Champ. 

Make sure when you're buying tubes to buy the correct amount that you need for your amp as well as the correct model of preamp and power amp tubes.

The Pros of Solid State Amps

Although lots of guitarists will tell you that they prefer the sound of tube amps, there's lots of redeeming qualities of solid state amps that make them an appealing choice for many people.  The technology behind solid state amplifiers allows them to be built much smaller and compact than tube amps.  These days, some solid state amps can fit in your gig bag or even on your pedal board.

Quilter is a company that makes tons of really fantastic sounding solid state amplifiers, and this Interblock 45 model is really mind blowing.  This 45 watt head is the size of a pedal, and it can power a 4x12 cabinet and sound great doing it!  I own one of these and I use it all the time for practicing with headphones, as well as a reliable backup for any amp at a gig.  

As well as being portable, solid state amps also embrace all sorts of new technology.  

this amp, called the BOSS Katana is not only compact but it is also wireless.  This amp also includes up to 50 BOSS effects.  This kind of technology can make solid state amplifiers an ideal choice for anybody who is new to guitar playing, because it allows you to learn about effects and signal chains before actually throwing a whole ton of money into that aspect of your playing.  

The Cons of Solid State Amps

In the past, a common grievance about solid state amps involved the way that they sound when overdriven.  While this certainly may have been true years ago, as time moves on I have noticed that the sound of overdriven solid state amps has been improving and I think that in the future this may not be so big of an issue.  It is true though that currently there really isn't anything like an overdriven tube amp.

One significant issue with solid state amps is that history just really isn't on their side.  What I mean by this is that no matter how good the technology behind solid state amps become, no matter how convenient they become or how good they sound in the future, Jimi Hendrix played tube amps.  The internet is full of photos of the best guitarists in history flanked on stage by a wall of Marshalls and mentally we all project ourselves onto that image.  All of our heroes used tube amps.  In a way, solid state amps are like the electric car of the guitar world.

Thank you as always for allowing me to be a super small part of your journey with the guitar, its something that I never take for granted.  If you've got any questions or concerns about this article or anything else guitar related, please don't hesitate to reach out or comment!

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