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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.

128x128zmann007
yakbob
449 posts
 

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.

johnss
564 posts
 

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. 

 

zmann007's avatar
zmann007 OP
8 posts
 

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.

 

 

zmann007's avatar
zmann007 OP
8 posts
 

Well, it appears I spoke too soon. The EVO 400 amp & pre developed a nasty ground loop hum / buzz that no amount of troubleshooting could cure. Indeed, the steady 20 - 25 dB bug zapper sound persisted, even after every source and peripheral was unplugged, including the sub. As soon as the amp came out of 'safe' mode, there it was.  Anyone experience anything similar?  Figure out a cure (short of installing a full solar array & getting off the grid)? I sent 'em back today, and am rolling the dice that I'll have better luck with the hybrid integrated EVO 300 Floyd. Fingers crossed....

atmasphere's avatar
atmasphere
11,629 posts
 

If the amplifier employs AC filaments for the voltage amplifier tubes, a cathode/filament short in a tube could cause that.

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