With the "IC-705 meets KPA-500" configuration from last weekend's DX contest still in place - and the Hardrock-50 in series - I couldn't help but wonder if I could use one amp to drive the other.
A quick check of the Hardrock-50's manual mentions one way of doing it:
In my case, I'm keying the HR-50 with its built-in COR function. The KPA-500 is keyed via a direct PTT cable from the IC-705 and I have a 20mS delay dialed in to the IC-705 to prevent the KPA-500 from being hot-keyed.
It works quite well.
On most bands, 1 watt of drive is required from the IC-705 to produce a 500 watt output. 20 and 30 meters require 2 watts drive.