I asked the makers of Powerpax a few questions and the second half of their answer was illuminating.
I bought the PowerPax because it was supposed to help load Tsunami's. This is obviously incorrect.
The bit about NMRA standards is indeed interesting and the suggestion is that the Tsunami is also not up to these standarrds?
The reason for the warning is that many people end up connecting the
program track to the main. This WILL damage the Power Pax. Using it
on an isolated piece of track is fine. The Power Pax cannot be used
to drive the locomotive. It meets the NMRA standard for program
track which requires that it not output more than 250mA. Any current
in excess of this will trip the Power Pax off requiring a reset.
This is to protect your decoder from damage in the event that there
is a mis-wire. If you are using the PR3 or the Sprog2, you do not
need the Power Pax. These units DO NOT meet NMRA program track
standards, so they have enough output power by themselves. The Power
Pax is designed to provide a boost to the normal program track
output without violating the 250mA requirement. Frankly, for
Soundtraxx decoders, you probably want to use the Sprog2. The reason
is that the program track on Digitrax is only on for a short time.
This on time is not long enough to get the decoder up and running,
and as a result, it is very difficult to correctly program
Soundtraxx decoders with Digitrax equipment.
Tony's Train Exchange