Some attenuators are resistive, others are reactive, but most of them are passive.
Passive means that the attenuator’s electronics does not require a power supply.
Resistive means that the power out of your amplifier is tamed by the presence of one or several resistors along the signal path. The load impedance plays a huge role on the sound, and a resistive attenuator will make the tone somewhat darker, with losses in the high and low frequencies.
Reactive means that reactive elements (transformers, coils and/or capacitors) are used instead of resistors. With this technology, the damping factor will decrease with the level of attenuation. Some of the time, a reactive attenuator means losses in character and fidelity, “muddy” sound and other unwanted effects.
Another downside of passive resistive/reactive attenuator is the way the listening level is controlled, usually by some stepped potentiometer, which does not allow for precise volume setting, and limits you to a set of fixed attenuations.
RE-ACT™ stands for “Reactive-Active Attenuator”, which means it uses a reactive load and active overall schematics. In effect, the RE-ACT™ can be described as the conjunction of two elements :
a reactive load-box inherited from the critically acclaimed Torpedo series, followed by
an ultra-low-distortion, wideband, low-noise solid-state amplifier based on a widely used HiFi architecture.
The role of this system is to present a speaker-like impedance to your amplifier, get rid of the power, then re-amplify it to the desired volume. This design offers a number of advantages over resistive/passive ones:
the amp is always connected to a fixed impedance, which is as close as possible to a real speaker impedance;
as the impedance does not change with the attenuation, the tone of your amp stays the same;
the volume you hear in the room can be set continuously, you get REAL master-volume control (SPEAKER parameter), after your amplifier’s master volume;
the speaker-output impedance of your amplifier is independent from the speaker impedance of the actual speaker cabinet you plug on the Torpedo Reload. This opens up a great many fun possibilities of cabinet mixing.