KT170 — Beam Tetrode, Octal | Tubeofile

KT170

Beam Tetrode — Octal

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Tung-Sol

↗ Radiomuseum

Known Equivalents & Substitutes

No known equivalents. If you know of any, use the ⚑ Report Issue button above.

Similar Tubes (Not Drop-In Compatible)

KT120

Same Tung-Sol octal beam tetrode family. KT170 has much higher Pa_max (85W vs 60W). Same pin functions but different operating points and heater current.

KT150

Same Tung-Sol octal beam tetrode family. KT170 has higher Pa_max (85W vs 70W). Same pin functions but different operating points.

Electrical Specifications

Absolute Maximum

Anode Dissipation (max)Anode Dissipation (max)85W

Screen Dissipation (max)Screen Dissipation (max)11W

Cathode Current (max)Cathode Current (max)300mA

Heater-to-Cathode Voltage (max)Cathode-Heater Voltage (max)300V

Max Grid ResistorMax Grid 1 Circuit Resistance0.51MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)400V

Screen Voltage (typical)Screen Voltage (typical)225V

Grid 1 Bias VoltageGrid 1 Bias Voltage-14V

Anode CurrentAnode Current155mA

Screen CurrentScreen Current (max)

Output

Output PowerOutput Power (SE)24W

Load ImpedanceLoad Impedance3,000Ω

other

First Grid Reverse Current (max)First Grid Reverse Current (max)1.2µA

First Grid Alternating Voltage (efficacious)First Grid Alternating Voltage (efficacious)9.9V

First Grid Cut-off VoltageFirst Grid Cut-off Voltage-60V

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current1.85A

Notes

The Tung-Sol datasheet is notably incomplete: no explicit Va_max or Vs_max ratings are specified. The operating conditions limits section lists Pa_max, Ps_max, Ik_max, Vhk_max, and Rg_max but omits maximum plate and screen voltages. The plate characteristic curves extend to 500 V.
The datasheet specifies only a single SE operating point (Va=400 V, Vg2=225 V). No push-pull operating conditions are provided despite the 300 W PP claim.
Pin 1 is the outer metal screen (electrostatic shield). Pin 6 is empty (no physical pin). Pin 8 is cathode with beam-forming screen connected internally.
Heater current is specified as a range of 1.75–2.0 A. Radiomuseum.org lists a typical value of 1.85 A.
First grid cut-off voltage is −60 V (at Va=400 V, Vg2=225 V).
No triode-strapped operating data is published by the manufacturer. A diyAudio user (KoitoYuu) traced triode curves but did not publish mu, gm, or ra values. The user measured interelectrode capacitances in triode mode: Ck-g1=25 pF, Cg1-g2=18 pF, Ck-g2=20 pF.

Pin Layout — Octal

1Outer Metal Screen

2Heater

3Plate (Anode)

Socket-Compatible Tubes ⚠ Not electrically compatible

6L6 KT120 KT150 KT63

References