Scoping the tuners

Marantz 2130 scope showing Kenwood L-1000T

Not long after I had the Kenwood L-1000T hooked up to my Sonos system, and was listening to it in the Kitchen (comparing it to the Marantz 2130 I just recently reinstalled in the kitchen) I decided I'd like to see the "Stereo" scope display of the Kenwood.  The Stereo display plots L vs R, so you see a diagonal line when there is mono, and something like a big fuzzy blob in stereo.  It's a visible measure of stereo separation.

So I hooked up the CD-R output of my Yamaha receiver to the scope inputs on the Marantz.  That lets me scope anything playing on my kitchen system, including the Marantz itself, using the EXT mode on the scope selector, but I can also view the Marantz itself using the Audio mode on the scope selector.

Marantz 2130 scope showing Marantz on EXT

It often seemed to me like the Kenwood might show less separation.  (Consider the pictures above for illustration only, they weren't taken simultaneously.)   The EXT Level controls on the Marantz scope are somewhat non-linear, but I adjusted the control so that the scope display looks mostly identical when switching between the EXT display when the Marantz itself is playing, and then to the AUDIO display which is showing the stereo display from the Marantz itself (not going through the Yamaha receiver).  I could get those two to look the same, but input from the Kenwood still looked different.

That is not how it sounds.  The Kenwood sounds like it has just as much separation, and has even more depth.  So is it that the Marantz is separating even what shouldn't be separated?  I'm thinking along those lines.

I believe the Sonos system is doing an accurate job of delivering the audio in 16 bits with no compression, which is how I have set it up (unless it got changed somehow).