I believe there have been two: roughly 1960-75 and 2010-present. Here's my reasoning.
Stereo was new in the mid-to-late 50's but by 1960, all of the primary manufacturers of the time - McIntosh, Harman Kardon, H. H. Scott, Fisher Radio, Sherwood - had multiple, fine-sounding components for sale. Good speakers ranged from AR-2's and KLH 6's to ginormous Bozaks and Klipschorns. The record companies had finally (almost) figured out how to record in stereo (still too many hard left/hard right/no center offerings). As time progressed, good stereo equipment became available to the middle-class. And that fostered the stereo boom of the late 60's/early 70's.
For most companies, stereo after 1975 became a commodity, so quality went down dramatically. Yes, there were the Audio Researches and, of course, McIntosh, to carry the flag for the audio aficionados. But, generally, the gear was lousy.
Now, although most aspiring audio aficionados can't afford the best (or even second-best), I believe we are in a new Golden Age. The incredible progress in speaker design and manufacture, new circuit topologies, the revitalization of vinyl and the advent of high-quality streaming has created this new age. Unfortunately, only the truly obsessed or the very wealthy can afford the great gear that's out there - which is the only tarnish on the gold.