The Tone King Ironman II is a 100w precision compensated reactive power attenuator with a sophisticated design that allows you to reduce the volume level at the speaker(s) while allowing the amplifier to operate at full output power.  The Ironman II preserves every ounce of the tone and feel of your amplifier, for natural power-tube overdrive and distortion. The 18 distinct attenuation settings let you choose the amount of output power that is being sent to the speakers, while the rest of the amplifier's power dissipates within the Ironman II.

What makes the Ironman II work unlike any other attenuator is the tuned reactive load and the transformer coupled power division circuitry.

Ideally, the load seen by an amplifier should have the appropriate complex impedance curve so that it responds as it does to a real speaker load.  A real speaker load varies greatly with frequency. For example, the impedance of a typical "8 ohm" speaker may rise to 60 ohms or more at its resonant frequency (usually around 60-80Hz), and then rise again to many tens of ohms at high frequencies.   An amplifier responds a lot differently when driving a complex load like this, compared to a simple resistive load (as is used in most attenuators).   Tone King developed the Ironman's reactive load circuit by matching the results of impedance curve measurements, ran on an actual speaker and then tweaked the resulting design through an empirical method in order to create a load circuit that is most effective at preserving the tone and feel of your amplifier.

The second part of the equation is the circuitry that divides the power from your amplifier between the speaker and the load.  In other attenuators, this is often done with a resistor ladder.  There are two problems with this approach - first, the resistor ladder itself can become a part of the load, which means that the amplifier sees a simple resistive load.  Second, in dividing the power this way, a voltage divider is effectively formed between the dividing network and the speaker.  Since the speaker has a complex impedance that varies with frequency, the result is that the frequency response at the speaker is altered, usually dulling the top end and muddying the sound.  To address this, the Iron Man II uses 100% transformer coupling via a set of custom audio transformers, so that the connection between the amplifier-to-load and between the amplifier-to-speaker is purely transformer coupled at every step of the attenuation dial.  This is an expensive and elaborate design (each step of the dial requires its own tap on one of the custom transformers), but is significantly more effective at preserving the tone and feel of your amplifier than other methods.