Amperex 6922 PQ, white label, made in USA, pinched waist (gold pins)
First version aver made. An absolutely gorgeous sounding tube with an unusual physical characteristic. The glass of the tube is actually slightly pinched at the about the point of the upper mica spacer. This reduces the tubes diameter at that point resulting in a subtle hourglass shape. The reason for this was for the bottle to actually clamp the upper mica space at its rounded corners resulting in a more rigid, less microphonic, structure. The result? A tube that defines the Amperex house sound: Lively, transparent & detailed with extended highs, yet absolutely no grain, with a punchy, dynamic bass. Mids lucid and palpable.