| Model ID | Williamson Type Amplifier W-4A, W4-AM |
| Signal Path | Analog Hardware |
| Dimensions | 38.7 × 17.8 × 22.4 cm (W × H × D) |
| Weight | 23.25lbs (Net), 28lbs (Shipped) |
| Power | 105-125VAC, 50/60Hz 115W |
| Frequency Response | 10Hz-100kHz ±1dB |
| Output Power | 20W |
| Maximum Average Output | 27W |
| Peak Power | 36W |
| THD (1kHz, 20W) | 1% |
| IMD (60Hz:3kHz, 20W) | 2.7% |
| SNR (0.25W) | 76.2dB |
| SNR (20W) | 95.2dB |
| Impedance Load | 4/8/16Ω |
| Feedback Factor | 22.6dB |
| Damping Factor | 28.5dB |
| Input Sensitivity (5W) | 1V |
| Output Tube | 5881 |
| Tube Complement | 6SN7GT (x2), 5881 (x2), 5V4G |
| Output Transformer | Chicago Standard Transformer |
| MSRP (1955) | $39.75 |
| Channels | 1 Channel |
