{"type_number":"3A/167M","canonical_url":"https://tubeofile.com/tubes/3A%2F167M","manufacturer":"Standard Telephones and Cables (STC)","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Loctal","description":"Indirectly-heated single-ended wideband repeater triode developed by STC for coaxial carrier system amplifiers. Features very high transconductance (47 mA/V) and low plate resistance (1000 ohms). Electrically identical to the Western Electric 437A but uses Loctal (B8G) base instead of Magnoval.","is_directly_heated":false,"completeness":"high","notes":["Manufactured by STC (an ITT associate company) in the UK. Designed for wide band repeater amplifier service in coaxial carrier telephone systems.","Also found use in high-quality audio applications, particularly as a cathode follower stage for matching condenser microphones to low-impedance mixing desk inputs.","Uses Loctal (B8G) 8-pin base. Pins 2 and 6 are internal connections; pin 3 is no connection.","Typical operating point: Va = 150 V, Vg = -1.5 V, Ia = 40 mA. At this point gm = 47 mA/V, ra = 1000 ohms.","The STC datasheet states this tube is identical with the American type 437A."],"references":["http://www.r-type.org/pdfs/3a167m.pdf","https://tdsl.duncanamps.com/show.php?des=3A167M"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aao0004.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=3A167M","radiomuseum":"https://www.radiomuseum.org/tubes/tube_3a167m.html"},"raw_equivalents":["CV5112"],"equivalents":[],"similar":[{"type_number":"437A","reason":"Western Electric equivalent — electrically identical per STC datasheet, but uses Magnoval (B9D) base instead of Loctal (B8G). Not pin-compatible.","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Heater","function_code":"h","notes":null},{"pin_number":"2","function":"Internal Connection","function_code":"ia","notes":null},{"pin_number":"3","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"4","function":"Plate","function_code":"a","notes":null},{"pin_number":"5","function":"Cathode","function_code":"k","notes":null},{"pin_number":"6","function":"Internal Connection","function_code":"ia","notes":null},{"pin_number":"7","function":"Grid","function_code":"g1","notes":null},{"pin_number":"8","function":"Heater","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"6.3","numeric_value":"6.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.45","numeric_value":"0.45","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"350","numeric_value":"350","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"7","numeric_value":"7","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"45","numeric_value":"45","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-1.5","numeric_value":"-1.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"40","numeric_value":"40","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1000","numeric_value":"1000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"47","numeric_value":"47","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"47","numeric_value":"47","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"4","numeric_value":"4","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"11","numeric_value":"11","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"2.5","numeric_value":"2.5","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:09:23.033Z"}