Tube vs. Solid-State Amplifiers - What's the Difference?

Posted by Greg on Aug 10, 2016

 

Tube vs. Solid-State Amplifiers - What's the Difference / Which is Better?

By Ben Bodine - MCM Electronics Product Manager for Pro Audio 

Solid-State vs Tubes?

Picking out the right guitar amplifier can be a confusing task. There is a lot of conflicting information out there and debates rage between players that prefer either the rugged reliability of a solid-state amplifier, or the rich responsiveness of a tube amp. So which one is better? Before we tackle that question, let’s take a look at the pros and cons, and the differences of each type.

What's the Difference?

All major guitar amplifier manufacturers build their amplifiers using either vacuum tube technology, solid-state technology, or some combination of both. You might also hear solid-state amplifiers referred to as “transistor” amplifiers, and hear tubes referred to as “valves” (mainly in Europe). But don’t worry, they’re just different words for the same thing. Physically, the main difference between solid-state and tube amps, is how they amplify the signal. Solid-state guitar amplifiers use solid-state electronics (diodes, transistors, etc.), while tube amps use one or more vacuum tubes to amplify the signal.

 

So what’s the difference in tone between the two? The main difference comes from overdriven tones (gain, distortion, break-up). Tube overdrive tends to be much smoother, richer and more responsive than solid-state. With a tube amp, even how hard or soft a player picks can influence the tone. Tube amps tend to be louder as well.

Even compared to a solid-state amp of the same wattage, a tube amp will be louder. This is important when trying to be heard and cut through the mix of a live band, but it has another benefit as well. Tube overdrive happens when the tubes are pushed hard. That means that the higher the volume, the harder the tubes are pushed. The harder the tubes are pushed, the more tube saturation you get. And tube saturation is what gets you that sweet tube tone that everyone strives for. This has caused a trend in the last few years for guitar players to switch to lower wattage tube amplifiers. Why? Because the point of break-up and tube saturation happens much quicker on a 30-watt amplifier, than it does on a 100-watt amplifier. So it allows you to achieve that saturated tube tone without ruining the hearing of yourself and everyone else in the general vicinity. Many guitarists are using this approach both for recording in the studio, as well as in live performance situations. Preferring to close-mic their amplifier to capture the overdriven sound of a small, low wattage tube amp, and send that signal to the recording console or PA mixing board.

 

Clean tones on a tube guitar amplifier have been described as being warmer and more organic than that of a solid-state guitar amplifier. But this is one area where the two types are very closely matched. So with all the great tones that you can get from a tube guitar amplifier, why would you want to get a solid-state guitar amplifier? There are actually many benefits to solid-state amplifiers. In the past, to get even close to the tones of your favorite professional player you had little choice but to purchase a tube amp. But today, solid-state amplifier technology has all but caught up to the tube market. Modeling amplifiers can now let you dial in tone from a specific brand, model, and even year of tube amps. Solid-state amps now also have sophisticated circuitry designed to emulate and act like tubes. But just like anything else, some are better at it than others.

Solid-state guitar amplifiers are generally less expensive to purchase than tube amplifiers and are also less expensive to maintain. Tubes have a limited life span. Much like light bulbs, they can go out at any time and will need to be replaced. Solid-state amplifiers can go years without little to no maintenance at all. Tubes are also fragile. When the guy helping you load your gear into the next gig accidentally drops or bangs your amp on the way to the stage, you will be left trying to figure out why your amp suddenly doesn’t want to work.

Which One is Better?

Can you hear the difference between a solid-state guitar amplifier and a tube guitar amplifier? Maybe. Maybe not. It really depends on your ear and what kind of tone you are trying to achieve. But which one is better? There’s really no right answer here. Good tone can be achieved with both solid-state and tube amplifiers. In the end, it comes down to 3 things. What sounds good to you, what works for your situation, and what you can afford.

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Comments (7) -

jtking@zoho.com
jtking@zoho.com
8/11/2016 8:52:05 AM #

I was an engineer at still famous amplifier manufacturer back in the 70's when we studied the difference in sound between solid state and tube amplifiers. You can throw out the gobbledygook talk because what was found was that tube amps have higher 2nd harmonic distortion when driven hard which provides a warm mid bassy sound. None the less distorted. Transistors do not over drive as easy and reproduce the sound more accurately (What you put in is what you get out.) Second harmonic distortion is actually pleasing to the ear - that is why we like stringed instruments after all. It is also why many guitarists like the tube distortion sound. The great news is that you can reproduce the same distortion in transistor amps by using Field Effect Transistors as they can be operated like tubes in a properly designed circuit. So, if you know what you are doing, you can have both worlds, the low cost and dependable solid state with lots of 2nd harmonic distortion.
JT  

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jmobley947
jmobley947
8/11/2016 10:58:07 AM #

Good analogy on harmonics. I've been professionally repairing both types of amps since the mid 60's. I might add this observation: tubes have a resonant quality at certain frequencies (frequency response) that most transistor amps lack.This is due to harmonics but also the internal construction of tubes by nature themselves have a tendency to reverberate. They kind of lengthen tones for a few nanoseconds that adds to "ear response", especially to musicians. Bose made his fame on "dithering" selected frequencies so the ear can detect them more easily because they exist longer.
Jim Mobley
Patrickselectronics.com

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FurryOne
FurryOne
8/11/2016 9:02:21 AM #

Even compared to a solid-state amp of the same wattage, a tube amp will be louder.

Not unless Ohm's Law changed!  More than likely you are referring to differences in how tube vs solid state amplifiers are rated for wattage - Tube Manufacturers have a tendency to be more "conservative" with their power ratings.  All this Tube vs SS was hashed out back in the late '70's by Bob Carver who, in his 4th Company has decided to pander to the tube aficionados.

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kwilliams538
kwilliams538
8/11/2016 9:39:49 AM #

As a retired electrical engineer specializing in analog electronics, I feel qualified to explain why a tube amp sounds louder than a SS amp of the same power out (watts). The undistorted outputs are equally loud, but most SS amps sound harsh when overdriven. Thus you don't push the SS amp to its limits. When a tube amp is overdriven to its limits, there can easily be 40-50% more power in the harmonics, but you have to like the sound of overdrive. As an electric-acoustic guitar player, I strive to have the amplified sound reproduced exactly like the guitar sounds unamplified. That requires no overdrive. So for those of us with that goal, the SS amp is the clear choice. Rugged, clean, distortion free, and never even close to overdrive. This means I need an amp with up to twice the power of the overdrive musician to achieve the same loudness, but distortion free.

It also means I need really good pickups in the acoustic, and I say pickups, PLURAL, as only the high end electric-acoustics combine different PU technology to achieve a sound comparable to playing through the best condenser microphone. Now if only I had one of those high end guitars....... and could play like Clapton "Unplugged."

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edwag3560
edwag3560
8/11/2016 2:45:49 PM #

Actually, it all breaks down to rough and smooth.  Analog signls use a smooth waveform that can reproduce EVERY tone and all in between.
Digital signals are rough.  All being based on 0's and 1's a square wave can not produce EVERY tone.  The nature of having to turn on and off instead of a ramped approach which is close, but still not true analog.
The same goes for digital cameras in case you care.  A digital image is made up of 0's and 1's each with an edge so halftones etc are not possible, wheras with film grain, or an analog TV signal, there is no end to the possible colors.  That is why the higher definition a picture is shown in, the more real it looks, but can not re-produce the range of analog.

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FurryOne
FurryOne
8/11/2016 3:21:48 PM #

Actually, it all breaks down to rough and smooth.  Analog signls use a smooth waveform that can reproduce EVERY tone and all in between.  Digital signals are rough.  All being based on 0's and 1's a square wave can not produce EVERY tone.

Ummm, I think you forgot Class A, AB, B, & C, and went directly to D through T without stopping to collect $200.  Tong

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kwilliams538
kwilliams538
8/11/2016 9:34:20 PM #

FurryOne makes a good point about the square waves not reproducing every tone. But if the sampling speed (as in digital recordings) or clock speed in a class D amplifier, is fast enough, and if the filters after the digital to analog conversion are sharp enough, low distortion 20 Hz - 20 kHz is achievable. That covers the lowest notes or tones, to the highest notes with all their harmonics. (Most people do not hear harmonics above 20 kHz.)

When Sony and Philips got together to standardize the compact disk, they fell short of achieving 20 kHz with no distortion. Blind tests have proven that trained ears can hear the improvement when the sample frequency is about double the compact disk sample frequency. Yes it is still a series of square stair steps before it hits the final filter, but proper filtering can make HD digital audio sound as good as analog.

Funny that this discussion started with tube vs. SS guitar amps, including talk about overdrive, to a discussion of analog vs. digital as it relates to high fidelity. Overdrive is low fidelity. It is distortion. But much of pop music is dominated by feedback, distortion, and overdrive. Go figure.

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