what does this mean?

It just means that neither are connected to the case ground or each other.

You can’t pad them down to unbalanced (3 wire) headphones. You’d need all four in an unbalanced config.

I have know exp, just interest, please report impressions.

My Pass Xa-25 amp is also DC coupled. Pass warns to unplug the amp when attaching speaker cables. Shorting either side to ground (case) could cause unspecified damage.

DC coupling has nothing to do with an output stage being bridged. You should always shut down fully when attaching cables. Shorting cables is the worst thing you can do to a live solid state amp. Although I wasn't aware the XA25 was a bridged design.

When an amp is bridged both binding posts carry signal (hot), neither is grounded. Shorting to ground will blow the amp. This may be a problem with some subwoofers if one speaker level is grounded.

@mcanaday  Margot will be very interested to see how you like your system! 

Yeah. I've written the guidebook book on what NOT to do with Leo's old BOSC Amplifiers. Personally, I prefer the Ultra Amplifier. More WPC and Tons of protection.

Yes, leave the Amp on all the time is fine if your Preamp or Line out from an AVR/ AV Preamp is also left on all the time. Those loud 'Pops" when you hot swap stuff on those little Amps can and in my case, will fry a driver (or two). Not to mention cause the Amplifier to go up in smoke.

While I love the sound those little 150W Wonders make. They couldn't drive my Series 1 901's. But the Ultra does !

Let's decouple the various things in that sentence - and push DC coupling to the side.

But the balanced modulator and differential power stage are linked and relevant.  A class-D (digital) amp is basically a big honkin' DAC that drives your speakers, with the speakers as part of the final low pass ("reconstruction") filter.

99% of amps are unbalanced which means that the power is created between oen speaker terminal ( the red one) and ground ( the black or green one).  A balanced interface (regardless of whether it is low level interconnect or to the speaker) is differential with two mirror-image signals. The load (speaker in this case) sees + and - versions of the same thing. NEITHER is ground. While one is going high, say to +10V the other is going low to -10V. So, if you ground either one by mistake, you have shorted your amp.  Since the speaker has no ground and is an insulated (wood) box, it floats.  No issue.

You do need to ensure that you maintain proper polarity which can be more confusing - but i expect this amp is marked clearly.

So unless you are doing something unusual (bi amping for example) - not much to concern yourself with.

G

Not to be technical, simply hookup the speakers, observing all polarity markings, and play. Avoid speaker selector switch boxes, and don’t try to play headphones off  the amps speaker outputs, not that it’s likely you would.  Any normal audiophile setup is perfectly OK.  If you want to use a REL sub, do not connect the black wire to anything, just tag the red and yellow to the amps’ + terminals. 

@mcanaday 

Both speaker output hot, it no different than any other differential output amplifier. The output of the amplifier is bridged.

Thanks for the reassurance, everyone.  I've placed an order!  Everything is back-ordered so it will be a while, but I'll report back when I have it set up.

cheers,

Margot