Primare 928 Monoblock design

Hi,
Is anyone on this forum familier with the Bo Christensen designed Primare 928 amplifiers, and if so can you answer a question for me?

Are the Primare 928 Monoblocks a 'differential' design or not? The answer to this question is critical to my approach when adding a pair of subs to my system.

I have received some good advice on another thread about things I can do to safely connect in the event that the amps are a differential design, but it would be useful to know one way or the other.

I bought these amps on Audiogon many years ago, but don't have the manuals and can't find them on the internet.

Any help appreciated