The LD-777 really belongs in the Invisibilia section of TVK but since it was (somewhat) (once) advertised in a catalog, like Alpine's DAT-8200, one can assume JVC really intended to market its ELCASET recorder. At least for a short while.
As proof is the existence of the VELD-1 prototype shown at the Japan Audio Fair in october 1977 : a monster two-box item, the first part being the EL recorder itself with eq/bias, levels and VUs, the second being the programming, dual digital displays and transports keys.
A rapidly gone prototype, visually very different than the LD-777(SA), which was probably planned for broadcast uses.
The LD-777 high-end recorder should have been available in two yet again different flavors : either as a two-box component (drive in one, electronics and i/os in another) or as a complete item.
The first possibility was retained for the one (and only ?) (last ?) (presumed ?) pre-production sample : the two boxes are separated but fit into a single enclosure.
Technics and Teac also hesitated between formulas (the two RS-7900 prototypes vs. the final RS-7500) and, at JVC, the remaining part of this hesitation is the dual name LD-777 and LD-777SA.
Inside are all the late 1970s JVC goodies : Sendust-Alloy heads, ANRS and Super-ANRS noise reduction system and ID mechanism (Independent Drive).
Super ANRS mainly deals with high frequencies, above 1Khz : compressing them during recording, expanding them at playback, lowering distortion along the way (less than 3% at +5VU and 10Khz, and eliminating bias vs. signal beating as well.
ANRS works automatically during playback, even on tapes recorded with another NR system.
The electronics allow left & right 400Hz sensivity and bias calibration, 400Hz and 15Khz test signals, MIC/line mixing and, of course, tape/source monitoring.
Tape type selection is automatic as planned on Sony's EL-7 but carried over to the EL-4 only.
The drive part allows memory play/stop and the switching of LED peak indicators, à la Luxman M-6000.
Build-quality seems to have been more than excellent, the least one could do for this ultimate cassette format, but since only one single image was ever published and no specifications at all... it is difficult to asses in detail !
Like the VELD-1 prototype, the ELCASET LD-777 almost made it, too late, and went.