6AJ8
6AJ8 is also designated ECH81. Completed sales put the typical price at $18.50 per tube.
The 6AJ8 is a triode-heptode vacuum tube with a coated unipotential cathode, intended for use in F.M., AM/FM, A.M., and television receivers.
Construction
The 6AJ8 is mounted on a small button noval 9-pin base. Its maximum overall length is 2 5/8 inches, with a maximum seated height of 2 3/8 inches. The bulb length excluding tip is 2 3/32 inches, and the maximum diameter is 7/8 inch. The tube may be mounted in any position.
Ratings and Characteristics
The heater requires 6.3 volts at 0.3 ampere. The basing connections follow the JETEC designation 9CA. Pin 1 connects to heptode grids No.2 and 4; pin 2 to heptode grid No.1; pin 3 to the cathode, heptode grid No.5, and internal shield; pins 4 and 5 to the heater; pin 6 to the heptode plate; pin 7 to heptode grid No.3; pin 8 to the triode plate; and pin 9 to the triode grid.
Interelectrode capacitances include 4.8 picofarads from heptode grid No.1 to all other elements, 7.9 picofarads from heptode plate to all other elements, and 5.8 picofarads from grid No.3 to all other elements. Maximum capacitances are 0.01 picofarad from heptode plate to grid No.1, 0.3 picofarad from grid No.1 to grid No.3, 0.1 picofarad from grid No.1 to heater, and 0.08 picofarad from grid No.3 to heater.
The N.V. Philips' Gloeilampenfabrieken datasheet gives an equivalent noise resistance of 8500 ohms and an input damping at 100 Mc of 1600 ohms for the 6AJ8.
| Designation | Evidence | Confidence |
|---|---|---|
| ECH81 | 73 independent documents | strong |
Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.
| Measure | Per tube |
|---|---|
| Median | $18.50 |
| Typical range (25th–75th) | $13.95 – $38.94 |
| Most sales (10th–90th) | $11.95 – $48.24 |
| Extremes incl. outliers | $7.25 – $67.54 |
| Completed sales | 35 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Telefunken | $17.77 | $16.95 – $47.03 | 8 |
| Philips | $11.97 | $11.95 – $17.90 | 4 |
| Valvo | $41.64 | $41.28 – $54.39 | 4 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $22.10 | 15 |
| used | $15.50 | 14 |
Per-tube prices from completed sales, 2026-06-29 to 2026-09-18. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 6AJ8, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Philips | 6AJ8 | PDF (745 KB) |
| Hitachi | 6AJ8 | PDF (83 KB) |
| Tesla | ECH81 | PDF (8830 KB) |
| Mazda-Belvu | ECH81 | PDF (510 KB) |
| Philips | ECH81 | PDF (496 KB) |
| RFT | ECH81 | PDF (184 KB) |
| La Radiotechnique | ECH81 | PDF (106 KB) |
| Philips | ECH81 | PDF (97 KB) |
Documents held here and used to write this page.
- 6 A J 8
- Mezní hodnoty: (filed under ECH81)
2 further designations appear alongside 6AJ8 in the literature but below the evidence threshold used here, so they are not listed as equivalent.