6K7

6K7 is also designated 6K7G. Completed sales put the typical price at $8.52 per tube.

Description

The 6K7 is a variable-mu (remote cut-off) pentode amplifier intended for RF and IF amplifier stages in radio equipment, where it is suitable for use with automatic volume control (AVC) and minimizes cross modulation. The Tung-Sol datasheet describes the 6K7 and 6K7GT as variable-mu pentode amplifiers in octal metal (glass) construction; the Brimar datasheet describes the 6K7G and 6K7GT as indirectly heated pentodes of the vari-mu type. The 6K7 has a glass bulb, while the 6K7GT has a metal sleeve; the 6K7GT has pin 1 connected to the metal shell. The tube uses a small wafer 7-pin octal base and may be operated in any mounting position. The cathode is coated and unipotential.

Ratings

The heater is rated at 6.3 volts and 300 mA, AC or DC. Maximum ratings include a plate voltage of 300 volts, a grid #2 voltage of 125 volts, a grid #2 supply voltage of 300 volts, a plate dissipation of 2.75 watts, a grid #2 dissipation of 0.35 watts, and a maximum heater-cathode voltage of 90 volts.

Capacitance

For both the 6K7 and 6K7GT, the maximum grid-to-plate capacitance is 0.005 μμf (also given as 0.005 pF for the 6K7GT). The output capacitance (P to H+K+G2+G3+S+IS) is 12 μμf for both types. The input capacitance (G4 to H+K+G2+G3+S+IS) is 7 μμf for the 6K7 with shell connected to cathode, and 4.6 μμf (4.6 pF) for the 6K7GT. For the 6K7GT, capacitance measurements use an external shield #308 connected to pin 1 and pin 8.

Typical Operation

Characteristics are given at several operating points. At a plate voltage of 100 V, grid #2 voltage of 100 V, and grid #1 voltage of −1 V, the plate resistance is approximately 0.15 megohm, transconductance is 1650 µmhos, plate current is 9.5 mA, and grid #2 current is 2.7 mA. At a plate voltage of 250 V, grid #2 voltage of 100 V, and grid #1 voltage of −3 V, the plate resistance is approximately 0.8 megohm, transconductance is 1450 µmhos, plate current is 0.7 mA, and grid #2 current is 1.7 mA. At a plate voltage of 250 V, grid #2 voltage of 125 V, and grid #1 voltage of −3 V, the plate resistance is approximately 0.6 megohm, transconductance is 1650 µmhos, plate current is 10.5 mA, and grid #2 current is 2.6 mA. The grid #1 voltage required for a transconductance of 2 µmhos is approximately −38.5 V at the first point, −42.5 V at the second, and −52.5 V at the third.

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.

Per-tube prices from completed sales, 2026-08-21 to 2026-09-24. Matched pairs and quads are divided out. See the price index for how these move over time.

Original manufacturer datasheets for 6K7, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• - TUNG-SOL -
• VARI-MU R.F. PENTODES (filed under 6K7G)

1 further designation appears alongside 6K7 in the literature but below the evidence threshold used here, so it is not listed as equivalent.