2A3
2A3 has no equivalent designation confirmed by the archive. Completed sales put the typical price at $100.00 per tube.
Description
The 2A3 is a directly heated power amplifier triode with a coated filament rated at 2.5 volts AC or DC and 2.5 amperes. It is intended for use as a Class A1 amplifier.
Construction
The tube has a four-pin base with the following pinout: pin 1 is filament, pin 2 is plate, and pin 4 is filament. Direct interelectrode capacitances are approximately 16.5 pF from grid to plate, 7.5 pF from grid to cathode, and 5.5 pF from plate to cathode.
Ratings and Operating Characteristics
At typical operating conditions of 250 plate volts and −45 grid volts, the 2A3 exhibits an amplification factor of 4.2, a plate resistance of 800 ohms, a transconductance of 5250 micromhos, a plate current of 60 milliamperes, and a load resistance of 2500 ohms. Under these conditions, second harmonic distortion is 5 percent and power output is 3.5 watts. The maximum grid-circuit resistance is 0.05 megohm with fixed bias and 0.5 megohm with cathode bias.
| Measure | Per tube |
|---|---|
| Median | $100.00 |
| Typical range (25th–75th) | $66.30 – $166.50 |
| Most sales (10th–90th) | $48.43 – $315.00 |
| Extremes incl. outliers | $21.07 – $844.17 |
| Completed sales | 313 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| RCA | $107.22 | $72.90 – $179.97 | 135 |
| Sylvania | $104.53 | $78.00 – $193.05 | 36 |
| Ken-Rad | $133.60 | $73.02 – $199.47 | 19 |
| Raytheon | $140.39 | $90.01 – $290.35 | 16 |
| Tung-Sol | $92.07 | $56.95 – $121.95 | 14 |
| GE | $57.87 | $40.94 – $88.47 | 11 |
| National Union | $62.56 | $58.95 – $114.97 | 8 |
| Electro-Harmonix | $79.62 | $49.99 – $126.37 | 7 |
| Shuguang | $47.19 | $39.99 – $82.00 | 6 |
| Marconi | $94.75 | $88.69 – $101.35 | 5 |
| Westinghouse | $62.63 | $39.99 – $74.00 | 5 |
| Philco | $100.17 | $57.95 – $102.00 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $125.99 | 93 |
| used | $88.58 | 158 |
| current | $83.46 | 22 |
Per-tube prices from completed sales, 2026-04-04 to 2026-10-17. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 2A3, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| RCA (HB3) | 2A3 | PDF (193 KB) |
| Tung-Sol | 2A3 | PDF (166 KB) |
| RCA | 2A3 | PDF (139 KB) |
| Sylvania | 2A3 | PDF (19 KB) |
Documents held here and used to write this page.
- 2A3
1 further designation appears alongside 2A3 in the literature but below the evidence threshold used here, so it is not listed as equivalent.