Pass Labs “House Sound” vs. McIntosh “House Sound”

Not sure what might be causing that.

If the analog jumpers are set for too high an output the symptom would be distortion, not hum, and only when the combination of the volume of the music and the setting of the DEQX’s volume control is too high.

I assume that you don’t have the analog main outputs of the DEQX disabled in the configuration, and that you disconnected the XLR cables from the amps when you connected the RCA cables.

Beyond that, I see the following statement on page 160 of the latest version of the DEQX manual, regarding the 75 ohm specification of the output impedance of the unbalanced analog outputs:

[The unbalanced analog output impedance is 75 ohms] into an earth-referenced amplifier i.e. one where the RCA ground pin connects to mains ground. This is normally the case. The precise output impedance is 75 ohms, plus 75 ohms in parallel with whatever the amplifier puts in series between its RCA connector and mains ground. If the latter is open, then the impedance can be as high as 150 ohms (such as may happen with a two-pin power connector).

I’m not quite sure what to make of that, but perhaps there is some kind of incompatibility between the internal grounding schemes of the DEQX and the amps. Which in turn may only manifest itself when unbalanced interconnections are used between the two components, since balanced receiver circuits can be designed (and ideally should be designed) to ignore ground.

That’s about all I can think of at this point.

Best regards,
-- Al

I own a Pass Labs X 250 for LR Focal floorstanding speakers a X260.5 for my center channel and large Focal Rear speakers that I Run with my X5. I know that your are asking about A Pass Labs XP 20 however In my opinion McIntosh does not come close to the build quality and sound reproduction of almost anything Pass Labs makes. Pass Labs CS is the best they STAND behind what they sell 
My AV is a Krell 707

I've never heard a Pass Labs but I might comment on McIntosh.  McIntosh's 'house-sound' might best be described as exceptionally smooth with a wide soundstage yet not too forward.   McIntosh has excellent build quality, resale value and often understated fact that all of their component visually match in terms of color scheme.  Nothing like having a full rack of matching gear.  Personally I don't care about those features and I've found other gear that sounds better to my personal tastes.  McIntosh is like the Apple of audiophile gear, well built and respected but not doing anything extraordinary.   An excellent well-rounded setup could include a Pass Labs X25, Schiit Yaggi DAC, and your choice of tube preamp (my preference would be Prima Luna premium or Conrad Johnson classic depending on budget).

I´ve not heard the mcintosh but have had the xp20 for some years now and also the same c4s you own. My experience is that most of the time break in is crucial, more so for this preamp.
Out of the box the sound was closed in ,dull and lifeless. So much so, that I felt I had made a mistake in upgrading ? from the pass xp1 after having achieved the performance I was already satisfied with.
But being forewarned by the dealer I reluctantly exercised patience and after what I believe to be several hundred hours ( the dealer advised 500 !) the sound opened up beautifully and have been content ever since. In fact it may be the only piece of equipment that I´ve  never felt the urge to change. At least until now and it has been with me for more than 5 years. 
The xp20 is a fine piece of equipment, dead quiet, with few if any rivals within its price range.

IMO