There are four models of transformers selectable on a 4-way Voicing rotary switch. There is an emulation of the ubiquitous and classic United Transformer Corporation's UTC 108 X and then the super rare German-made Malotki E4M 4001B transformers that can sell for $600 a pair and used in Neumann recording/mastering consoles. Positions 3 and 4 are the super-expensive Haufe v 178 transformer and the Western Electric WE111c.

There are few controls. The Strength knob is for control over the transformer's linearity--it dials in the "color" of the process without loss of headroom. There is the ability to change the Input impedance between Unity (default) with no throughput gain increase and then Boost with an emulated level increase only possible with hardware transformers with multiple primary windings. The Morph switch enables harmonic structure morphing when changing the main Strength control.

Hardware transformers do not have these parameters available--they are passive devices and you get what you get. Before True Iron, you would have to buy a collection of different transformers old and new and connect them individually for a particular sound quality.

Other controls include a Wet/Dry control, Crush and Crush x2 for warm overdrive all the way up to distortion and breakup. This is the same as the sound of transformers pushed beyond their intended operating range. True Iron's controls finish with complete A/B facilities, preset save/recall management plus an Output level control in the lower right corner for dialing back radical levels often encountered when using Boost and/or Crush.

I installed and launched True Iron in a current mix session in Pro Tools 2018.12 HDX. I've been having trouble with the sound of a direct recording of a bass guitar given to me. Without the pleasure of just re-recording it, I had to make the best of it!

I ended up using the 4001B transformer mode that gave me cool sounding lower octaves. But I also liked the UTC 108 X transformer and used the Wet/Dry to dial back the increased mid-range "bark" I picked up. This sound ended up working better within the busy track to make the bass part speak out a little more! I ended up duplicating the track and using a mix of the two.