4 amps in the archive
The matching circuits, with the neighbouring topology choices shown for contrast.
| Circuit | Era | Output | Tubes | Output-stage bias | Rectifier | Tone stack |
|---|---|---|---|---|---|---|
| 5D3 | 1954–1955 | 12 W | 12AY7, 12AX7, 6V6GT, 6V6GT, 5Y3GT | cathode | 5Y3GT | single-knob |
| 6161 | 1960–1968 | 14 W | 12AX7, 12AX7, 12AX7, 6973, 6973, 5Y3GT | cathode | 5Y3GT | single-knob |
| B15N | 1961–1964 | 25 W | 6SL7, 6SL7, 6SL7, 6L6GC, 6L6GC, 5AR4 | fixed | 5AR4 | per-channel-tb |
| GA40 | 1956–1962 | 15 W | 5879, 5879, 6SQ7, 12AX7, 6V6GT, 6V6GT, 5Y3GT | cathode | 5Y3GT | single-knob |