Basics Of Power Attenuator
A power attenuator is designed to dissipate excess or unneeded power in the electric guitar amplifier. This will lessen the volume of sound generated by the speaker. With a guitar amplifier, distortion can be produced by overdriving the output stage. The amplifier will produce this distortion at or near its maximum output power. By reducing the power delivered to the speaker, the power attenuator can lessen the volume of sound generated by the amplifier to the user’s desired level.
There are several approaches to power attenuation. The “power soaker” approach is the most common method. In this approach, the attenuator absorbs part of the power while the remaining portion of the power is directed to the speaker. Another approach utilizes a Variac or a power scaling circuit to reduce the B+ supply voltage available to the power tubes. This Variac-based approach generates power tube distortion in a way that an adjustable power level is provided to the speaker. Meanwhile, the power dampening method uses a potentiometer and a phase inverter to control the output level.
Basically, the device has two components: a dummy load and a variable wattage-splitter control. A dummy load is referred to as equipment that is used for simulating an electrical load. Power attenuator may be purely resistive, mostly resistive, or partly reactive. The device maybe packaged as amp-top, rankmount or built into the head. It is also often packaged with full dummy load ability and a cabinet simulation filter. The device usually contains heat dissipation parts such as a fan, a vented case or a heat sink. The device may also include a line-level output jack which is used for sending the distortion-processed signal through an effects chain, or to a recording console. The line-level output jack may also be used to re-amplify the signal through a smaller or larger amplifier. There is a current debate on whether reactive-based attenuators are better in preserving the tone of the guitar amplifier as compared to other types of attenuators.
The Altair Attenuator is the original attenuator for guitar amplifier. It is primarily resistive and it uses a toaster coil with low inductance windings. The most popular power attenuators available in the market are the Marshall Power Brake, THD Hot Plate, Weber MASS and Scholz Power Soak.
The Marshall Power Brake adds some capacitance or inductance to the electrical load. The manufacturer of the Marshall Power Brake claims that it is the ultimate digital attenuator because it delivers great sound. Meanwhile, the THD Hot Plate features a dedicated line out with level control, treble and bass boost switches, and variable attenuation. The THD Hot Plate also absorbs majority of the amplifier’s signal and passes only small amount of the signal to the speaker, with the remaining power being converted to heat. The Weber MASS attenuator, just like other Weber attenuator products, is available in various models for different power handling applications. On the other hand, the Scholz Power Soak attenuator is purely resistive. This power attenuator allows the production of great sound at low volumes.
