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There are two basic kinds of amplification, vintage-style vacuum tube, and newer solid-state. While vacuum tubes and transistors can also be used for electronic switching, it is in terms of amplification, for the purposes of this section, that we're most interested.

Vacuum Tube Amplifiers

Vacuum tube amplification dates back to 1906, when Lee De Forest, the son of an Alabama Congregationalist minister, created the first "audion", or vacuum tube sound amplification device. As such, the vacuum tube of the 20th century actually shares a common lineage with the incandescent light bulb. De Forest accomplished the creation of the audion when he inserted a "grid" into a vacuum tube, and then applied a high-voltage electric current to the anode.

While we've done our best to explain the Thermionic Effect in plain English, the following may be a little technical for some, and it may take several readings to make sense. Please feel free to access other sources:

There are at least two poles to every electronic device. There is the Cathode, an area where electrons accumulate that becomes negatively charged, and the Anode, an area devoid of electrons. This lack of electrons causes the Anode to become positively charged. Any basic physics course will tell you that in an atom, electrons are negatively charged and protons are positively charged. You should keep in mind the convention that current direction is according to where a positive charge would move, not a negative charge. So, if electrons do the actual moving in a device, then current runs the opposite direction. So in discussing electrics and electronics, positive and negative refer to flow, not to the real atomic charge that physicists have assigned to the various atomic particles and the direction in which those particles are flowing.

So that having been said...

If a cathode is heated within reasonable proximity to an anode, an effect called "thermionic emission" takes place. This results in a stream of electrons from the cathode to the anode. When another component, called a "grid", is put in between the cathode and the anode, we're ready to get our amplification started. Finally, once a fluctuating electric current (for example, an electrical signal from a guitar or a microphone) is placed on the grid, that fluctuation causes the anode to see a corresponding variation in the thermionic emission effect from the cathode.

The thermionic emission effect in and of itself, is constant. In other words, the negatively charged cathode is always trying to stream electrons to the anode. With a fluctuating musical, or electrical signal on the grid, the voltage changes occurring on the grid cause corresponding polarity swings, both positive and negative. These polarity swings, in turn, cause moment-to-moment variation in the flow of electrons from the cathode to the anode. This is the amplified signal.

Creating Variations in the Thermionic Effect 
When the grid becomes negatively charged, the electrons flowing from the cathode to the anode encounter more resistance (or repulsion) at the also-negatively-charged grid. This resistance or repulsion must be overcome before those electrons can make their way to the anode. Conversely, when the grid becomes positively charged, the electrons not only flow from the cathode to the anode, but are even influenced to do so due to the corresponding attraction of the momentarily-positive field. This causes more electrons to be attracted and flow to the anode.

It was the genius of De Forest, whose insertion of a grid in a vacuum tube enabled variation in the thermionic effect (from the cathode to the anode) and in doing so, created the first electronic amplifier.

To be perfectly transparent, this website and company are called "Thermionic Studios" because of our appreciation of, and preference for, tube amps. While we might be amp snobs, we believe first and foremost that great music is made by great artists. Great equipment doesn't make a great artist. Great equipment supports great artists.

Vacuum Tube Amplifier Manufacturers

(Presented in alphabetical order)

Solid State Amplifiers

Solid state amplification refers to the fact that the transistor does not operate using any kind of vacuum nor does it require an emission of electrons. The transistor operates with semiconductors - everything is completely "solid" in a single block of material. There is no heating, there is no "emission". The transistor was first invented in 1948 at Bell Labs by John Bardeen, Walter Brattain, and William Shockley. Most solid state amplifiers are considered less-interesting because the nature of solid state components and electronic architecture usually render solid state amplifiers less accessible, and therefore less modifiable. Solid state amplification is also considered "less-musical" sounding due to odd-order harmonics being created as an effect of the nature of solid state componentry.

However, there are many things about solid state amplifiers that can make them more attractive:

  1. Solid state amplifiers tend to have a lower price than their vacuum tube counterparts.
  2. Solid state amplifiers tend to use less electrical power (not having to heat vacuum tubes) than their vacuum tube counterparts.
  3. Solid state amplifiers do not hold lethal voltages in their capacitors.
  4. Solid state amplifiers tend (again, due to the nature of the componentry) to be more durable and road-worthy than their vacuum tube counterparts.
  5. Solid state amplifiers tend to be lighter weight due to not having to need heavy iron electric transformers.
  6. Solid state amplifiers tend not to be as vulnerable to temperature or humidity changes as vacuum tube amplifiers.
  7. Certain brands and models of solid state amplifiers are highly respected by many significant artists.

Solid State Amplifier Manufacturers

(Presented in alphabetical order)


Yes, we are aware that there is a whole selection of other manufacturers that these lists do not touch upon. We are not necessarily against inclusion of other manufacturers. The criteria for inclusion on this list is when a piece of equipment is identified with and can be attributed to a sophisticated, interesting, musical, and/or popular artist (or piece of music) - a piece of music or artist that individual musicians, well-known, or amateur, are going out of their way to emulate.

We do not expect these lists to be exhaustive, and we do not claim to have perfect knowledge. We do expect these lists to be informative, and we readily accept input so as to make these lists more informative. If there are amps for which documentation is available for use with an artist or on a piece of music that is significant (our decision), we will be more than happy to include it.