If you have challenging impedance speakers such as electrostats and panel speakers this is a great accessory to have to broaden your options for amplifiers. The Autoformer options worked pretty well for me as I have Sandersound 10b speakers and with Autoformers, I was able to pair up good tube amps such as my Audio Research Ref 110 to drive these speakers.
Without the autoformers, it would be wicked load for the Ref 110 to drive as the impedance of the Sandersounds drop to 1/2 ohm at high freqs.
Here’s a link for more info…
Paul’s products have all been well reviewed and you can find a load of feedback; reviews on it.
I have perfect feedback on Audiogon and ebay, just check for the same username as I have here; so buy with confidence.