What is a Rectifier?
Due to the popularity of our Dual Rectifier® amplifiers, the term rectifier has become a bit synonymous with the performance these legendary high gain amps but what exactly is a rectifier and how can knowing more about this part of your amplifier be of benefit? A “rectifier” is a basic building block of all power supplies, and a “power supply” is a basic building block of all amplifiers (and most other electronics devices). The “power supply” takes AC (alternating current) voltage, arriving via the power transformer, and transforms it into usable DC (direct current) voltage needed to run an amp’s circuits. This job can be performed by “diodes” (small components on a circuit board that look somewhat similar to resistors), or by a “rectifier tube”.
With the invention of solid-state diode rectification in the early 1950s, diodes, being smaller, less expensive and more efficient (therefore providing a tighter response or “feel” for a player) became a common choice for rectification and the use of rectifier tubes in amp designs was somewhat phased out. However, when rectifier tubes are used instead of diodes, the power supply has more “sag” (and a slower response) and this can be felt by the player as a more vintage “string-feel”. As more power is consumed (you turning the amp up) an increased voltage drop occurs, resulting in the time-honored tube-rectified feel. The overall response is ‘spongier’ and causes the strings of your guitar to feel more elastic and often easier and ‘more juicy’ to play.
What if you would like to have the option of choosing from either type of rectifier, allowing you to customize the feel to suit your playing style? This has actually been a feature on a number of MESA/Boogie® amplifiers, since we patented the idea of Dual Rectification in the early 1990s and released the first Dual Rectifier® Head. Built into a Dual Rectifier design, we offer guitarists a means to choose between both types of rectifiers - Vacuum Tube or Silicon Diode.
Once again, keep in mind that while the choice of rectifier does have an effect on the responsiveness of the amp and therefore plays a role in arriving at your tone, rectifiers are not actually located in the audio path.
Also, don’t be alarmed that your rectifier tubes don’t glow as brightly as your audio tubes. While they may not glow as brightly as audio tubes, because they are conducting power, they will get hot and it is pretty easy to determine that they are working. If you switch an amp to its “Vacuum Tube” rectifier setting and it performs well, it is safe to assume the rectifier tubes are good. If at that point though the amp’s performance is weak or you blow a fuse, a rectifier tube is one possible suspect. They will wear out over time.