BIG Update:
Short Version:
The ELP can playback CD-4 LPs with all of the high frequency information in tact.
Long Version:
Boy, did it take me a while to get to this point. Back when I ordered my ELP in late April 2020, I ordered a passive inverse RIAA board from a company called Motronix out of Israel. (For those of you who haven't read this entire thread, my turntable only supplies a line out, but CD-4 dedmodulators need a phono level signal to work their magic.) Due to COVID-19 restrictions, the board was taking an inordinate amount of time to get to me, so I tried a number of workarounds that are documented elsewhere in this thread. None of the workarounds was particularly satisfying to me, so I decided to take matters into my own hands and build my own passive inverse RIAA adapter.
Fortunately, I'm not the only person crazy enough to have attempted this, so someone else had already gone through the trouble of creating the parts list and the gerber files for the PCB:
Side Project: Stereo Accurate Inverse RIAA from HIFISonix - Build - Muffsy Phono Kits . I ordered PCBs from PCBWay (who manufactured them extremely quickly and inexpensively) and ordered the caps, resistors, and miscellaneous parts from Mouser. Once the first wave of parts came in, I started assembling my board....no trivial task, since it involves surface mount soldering of many teeny tiny parts with my very non-steady hands. You all can probably guess what happened next:
The original fully-assembled board that I ordered in April finally arrived from Israel, more than two months from my original order date.
So, I excitedly hooked it up to my Marantz demodulator and shook with joy when the ol' RADAR light lit up like a Christmas tree. Alas, my enthusiasm was short-lived as things were not quite right. Separation on the left channels was good, but non-existent on the right channels. I was eventually able to determine (after much hair-pulling and swearing) that the Motronix anti-RIAA board was allowing the 30k carrier to pass through its left channel, but not its right. Big bummer!
After licking my wounds, I got back to my workbench and completed the assembly process of my homemade anti-RIAA adapter. Once complete, I hooked it all up to my Marantz demodulator and...hmmmm...something still isn't right. There's separation, but not to the degree I'd expect. No amount of adjustment is making a tangible improvement. In a last ditch effort, I connected everything up to my JVC demodulator that I thought was broken...and it worked! Channel separation is good, and overall sound quality is good. I've listened to a handful of CD-4 LPs so far and they all seem to be working and sounding great.
So, can an ELP laser turntable be used to playback CD-4 records with the high-frequency carrier information in tact? YES!