Voltage Pentode ·Pentode
6BK8
Low-noise miniature audio pentode designed specifically for the early stages of high-gain audio amplifiers.
- Sections
- 1
- Base
- -
- Socket code
- B9A
- Base pins
- 9
- Nominal heater
- 6.3 V / 200 mA
Description
Miniature A.F. pentode; low-noise pentode for early high-gain audio-amplifier stages. The source explicitly describes it for the early stages of high-gain audio amplifiers.
Socket description
Small-button Noval 9-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- -
- Socket code
- B9A
- Base pins
- 9
- Nominal heater voltage
- 6.3 V
- Nominal heater current
- 200 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
1 physical section, each with unique specifications.
Section 1
Pentode
- Plate resistance
- 5000000 Ω
- Transconductance
- 0.00185 S
- Max plate voltage
- 300 V
- Max screen voltage
- 200 V
Amalgamated Wireless 6BK8 miniature internally screened low-noise audio-frequency pentode for input stages of high-gain microphone and tape amplifiers. Heater 6.3 V 0.2 A (corrected from parent 0.3 A), nine-pin E9-1 base with 9BJ basing. Published maximum anode 300 V, screen grid 200 V, cathode current 2.6 mA; heater-to-cathode peak maximum 150 V. Approximate plate resistance 5 MΩ at anode 250 V/screen 140 V, and gm 1850 µmhos (0.00185 S) at plate current 3 mA. Typical low-noise service at anode 175 V with high-value anode loads and cathode bias. Cold unscreened interelectrode capacitances published; suppression of hum/microphony crucial. AC heater winding center tap recommended for low hum, internal screen and optional external shield. Typical input-referred hum <=1.5 µV under stated conditions.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.