OK, correct me if I'm mistaken, but a little googling appears to reveal that the CD-400 (but not the similar looking CD-400B) is basically a JVC 4DD-5 with an added auxiliary input. That given, I was able to find an instruction manual for a 4DD-5 and also rummaging through my as yet uncleaned/unfiled records the Marantz CD-4 calibration disc. Will it be obvious what I'm listening for with the 30 kHz adjustment? I will hook it back up later and report back... (don't want to do it now as everyone else is asleep and if I run the disc through the ultrasonic now I might be bludgeoned...)
Also, it sounds like I need to hook a pair of RCAs from the direct out to my receiver's phono stage to listen to 2ch, SQ, or QS. Can I leave the "DIRECT OUT" switch engaged all the time then without any ill effect in the "4CH AUTO" mode? (I understand that that will disable sound output in the "2CH" front panel switch position) Do I add a ground wire from the CD-400 to the receiver? Am guessing no as I see no mention of it in the booklet, but that seems counterintuitive to me. It does confirm that I should have "double stereo" in 4CH AUTO. Not clear whether that is supposed to be also true in 2CH or not.
Why am I doing this again...? this whole mess makes playing a simple LP seem so complicated.
I apologize if all of this is really basic for some of you, but please understand that I wasn't even in grade school yet when CD-4 died, and my parents were music lovers but neither wealthy nor audiophiles so I was not exposed to this stuff back in the day and I have literally no knowledge base other than what I've read online here and elsewhere.
As to the comment about PREFERRING double stereo - I get it. I just want to make sure that everything is working correctly and that my system can reproduce the sound exactly as intended. Then if I want to adjust that sound, sure, let's do it. Maybe even listen to a stereo disc with QS or SQ engaged. Coincidentally, I've noticed a similar issue with Spotify playback from my PC. Since I got this quad setup hooked up I changed my PC playback from a dedicated 2 channel DAC to a HDMI connection to my Oppo BDP-105 which then downmixes multi-channel sources to 4.0 and inputs into the (coming back around to topic) aux input of the CD-400. What I've found is, while the speaker check in my Linux sound preferences does exactly what I expect it do (that is, FL and FR play through FL and FR, center plays through both FL and FR, SL and SBL play through RL, SR and SBR play through RR, LFE plays through all speakers) when I actually play music over the HDMI connection, it plays through all speakers. Again, the effect is not unpleasant, but I really would like to have control of the situation.
Then, of course, once I get this all working, then I get to pull my QRX-7001 out of storage and test that. Then, see if my KR-9940 has been fixed yet... (no it was seriously not intentional to collect this much quad stuff)