IN THIS era of hybrid analog/digital recording (and full-blown retro analog-only projects), vintage gear has never been more prized—or more expensive. It seems as though music enthusiasts, engineers and producers of every age group today, enamored of the warmth and power of classic recordings of the ’50s, ’60s, and ’70s, are still looking to capture that mysterious, hard-to-define, sonic je ne sais quoi ( a pleasing quality that cannot be exactly named ) that gives old recordings so much life and presence.