The lines behind the circuits

History

A documented circuit is one moment in a line that ran for decades. This section places each amp in its family — the chain of revisions it came from and the ones that followed — as a dated, sourced era timeline. Most entries are history-tier: the model is placed and cited but its circuit isn't drawn yet. A few link straight to the fully documented circuit page. 8 lines, 49 models, 10 with a documented circuit.

History-tier entries record a model's place, era, tube complement and the change that defined it, with sources — but no redrawn schematic, verified operating point, or parts list yet. Those are the documented circuits, earned one at a time. Want to move an entry from history-tier to documented? Here's how to contribute a circuit.