The top of the D-series at the end of the 1970s - a large valve unit with three documented revisions (D-79A, D-79B, D-79C MKII).
Valve equipment: 400-500 V is present on the plates and stored in the supply after switch-off. ARC units are valve-matched at the factory - replacement sets must be bought as matched quads/pairs.
Marks that can be entered for this maker: Model / catalogue number, Model / catalogue number, British capacitor code (Hunts, Mullard), Japanese capacitor code (Nichicon, Chemi-Con, ELNA), EIA component code.
Nothing predates 1979; components only push the date later.
Sold-listing reading: fair EUR 3,300, good EUR 3,300, excellent EUR 6,000 EUR · 5 sold listings (thin sample — indicative only) · as of 2026-10-17. Asking prices only - these are live listings, not completed sales. 5 listing(s) in EUR observed on 2026-10-17 via the HiFi Shark marketplace aggregator; min/median/max of the observed asks are used as fair/good/excellent, which is a reading of the ask spread, not a condition grading. Listings in other currencies were seen and counted for the spread but are not converted here (see the journal): USD x1.
Evidence: ARCDB — Audio Research model database · HiFi Shark — live listings aggregator