This is an absolute gem of a plugin! I've never owned a separate guitar poweramp but I image this must be a really good approximation of how it would sound. My normal use for this is with a ampsim plugin that don't have a built in poweramp, Ignites own The Anvil and Mercuriall SS-12 are examples of this. It's also great to use on ampsims where you can bypass the built-in poweramp simulation.
Note that this one is not supposed to be used on it's own but in a signal chain after the preamp but before the speaker cabinet emulation. A typical scenario would be something like this:
On the front panel you have controls for volume, depth and presence. Increasing the volume gives you that nice poweramp saturation that to my ears sound really pleasing. Depth controls low-frequencies and presence (as usual) high frequencies.
Looking at the back of the plugin you find controls for:
tube bias voltage.
amount of sag.
feedback level (the amount of signal that goes from the output back to the input).
choice between different models of power amp tubes (EL34/6L6/KT88).
feedback (a model of the interaction between poweramp and speakers) and.
overall output level.
Tweaking the bias, sag and feedback controls allows you to have very detailed control of the poweramp characteristics and also how it feels to play.
Feedback control settings are dependent on what type of IRs you use - your really should read the manual for best results here :).
This is a great sounding power amp simulation with an outstanding level of tweakability. As far as I know there are no other dedicated VST powerampsims, so there is really no competition to compare it to. Hopefully someday someone will model a MESA 2:Ninety or something similar. But the lack in choice is not a problem when the only choice you have is as good as the TPA-1. Big thanks to Ignite for giving this away for free.
Ignite Amps updated a number of plugin to a new major version in 2018 at the same time incorporating newer modelling technology - I'm very much hoping that this plugin receives the same treatment.