Question on PrimaLuna EVO 400 Amp: Fully Balanced (Differential), or No?


I've just taken delivery of new PrimaLuna (separates) EVO 400 amp & pre, and need some informed advice in re: hooking up my single REL S/812 sub. The REL manual shows different connection schemes for Differential (fully balanced), as opposed to standard.  I do have balanced (XLR) interconnects from DAC to pre, and from pre to amp, and there's a switch on the back to select for XLR connections, which I've engaged.

I've checked the PrimaLuna owner's manual, and searched online, but I can't find any indication of whether the EVO 400 amp is "Standard" or "Differential" (fully balanced). Does anyone know for sure? The REL cable has 3 terminations, and in standard amps, the black ground wire is connected, whereas in Differential, it hangs loose, or "floats."  Any insight on this would be greatly appreciated.

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I have the Evo 300 power amp and I've connected my REL 212SE as shown on the REL website:
https://relsupport.zendesk.com/hc/en-us/articles/360001493114-Tube-Amp-Connection-Methods

Although the 300 and 400 have XLR inputs I don't believe they are dual differential designs internally.

while the evo 400s have XLR connectors, they are not fully differential designs. 

still a traditional design. 

a pretty easy way to measure it compare the black speaker output terminals reference to ground. if its at same potential cannot be fully differential. 

 

Confirming the above -- I heard back from REL yesterday, after they had reached out to the PrimaLuna Mothership.  The EVO 400 is a standard (not Differential) amp, and so -- at least in single sub, non-monoblock (stereo) configurations, the black ground wire is attached to (either) negative / ground binder post.  The REL does want the 8 ohm posts, though; Upscale was quire clear on that, and it seems to be working fine.