6F8G
6F8G has no equivalent designation confirmed by the archive. Completed sales put the typical price at $48.00 per tube.
Description
The 6F8G is a general purpose twin triode voltage amplifier containing two completely independent triode units in one bulb. It has a glass bulb and a small 8-pin octal base with a G-8G bottom view.
Ratings
The heater is rated at 6.3 volts at 0.6 ampere, AC or DC. Maximum plate voltage is 300 volts, and maximum plate dissipation per unit is 2.5 watts. The minimum control grid voltage is 0 volts.
Characteristics
At a plate voltage of 90 volts and a control grid voltage of 0 volts, each unit has a plate current of 10.0 mA, a plate resistance of 6700 ohms, a transconductance of 3000 µmhos, and an amplification factor of 20. At a plate voltage of 250 volts and a control grid voltage of -8 volts, the plate current is 9.0 mA, plate resistance is 7700 ohms, transconductance is 2600 µmhos, and amplification factor is 20.
Capacitances
For triode unit 1, interelectrode capacitances are: grid to cathode 3.2 μμf, plate to cathode 3.2 μμf, and grid to plate 4.0 μμf. For triode unit 2, they are: grid to cathode 3.0 μμf, plate to cathode 3.8 μμf, and grid to plate 3.6 μμf. With an external shield connected to cathode, capacitances between units are: grid 1 to grid 2 0.2 μμf, plate 1 to plate 2 0.4 μμf, and grid 2 to plate 1 0.1 μμf.
Construction Notes
Triode 1 is identified as the triode having its grid brought out to the base pin, while triode 2 has its grid brought to the top cap.
| Measure | Per tube |
|---|---|
| Median | $48.00 |
| Typical range (25th–75th) | $38.46 – $75.83 |
| Most sales (10th–90th) | $24.99 – $132.13 |
| Extremes incl. outliers | $2.00 – $355.00 |
| Completed sales | 109 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| RCA | $41.50 | $36.22 – $57.92 | 34 |
| Sylvania | $49.97 | $42.00 – $96.50 | 24 |
| Raytheon | $48.78 | $40.70 – $70.00 | 13 |
| Tung-Sol | $140.00 | $114.65 – $194.00 | 9 |
| National Union | $47.00 | $36.95 – $85.83 | 7 |
| GE | $38.65 | $36.00 – $42.00 | 5 |
| Mullard | $127.01 | $94.55 – $132.13 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $56.84 | 66 |
| used | $41.00 | 31 |
Per-tube prices from completed sales, 2026-02-12 to 2026-10-18. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 6F8G, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Tung-Sol | 6F8G | PDF (111 KB) |
| Sylvania | 6F8G | PDF (99 KB) |
| Ken-Rad | 6F8G | PDF (71 KB) |
| RCA (HB3) | 6F8G | PDF (41 KB) |
Documents held here and used to write this page.
- TYPICAL OPERATING CONDITIONS AND CHARACTERISTICS