{"type_number":"KT8C","canonical_url":"https://tubeofile.com/tubes/KT8C","manufacturer":"GEC / M-O Valve Co. Ltd.","tube_type_key":"beam_tetrode","tube_type_display_name":"Beam Tetrode","base_name":"B5B","description":"Power beam tetrode designed for RF power amplifier and audio use, specified for RF service up to 100 MHz. British equivalent of the American 807, based on the KT66 design but with a longer electron path. Features a ceramic base cap for improved insulation in humid and aircraft environments.","is_directly_heated":false,"completeness":"medium","notes":["The KT8C is the ceramic-base variant of the KT8, intended for service in humid conditions and aircraft installations. CV1079 is the UK military designation assigned in 1941.","Top-cap anode connection — essential for the high-voltage insulation required in RF and transmitter service.","The r-type.org data lists operating parameters at maximum conditions (Va=600V, Vs=300V); typical AF operating points will be at lower voltages.","Described as 'a not very successful British attempt to emulate the American 807' — the longer electron path limits high-frequency performance compared to the 807 (65-100 MHz vs 125 MHz), though audio performance is considered excellent by some users.","Introduced in 1938. The KT8 family saw wartime RAF service as VT79 before being standardised as CV1079."],"references":["http://www.r-type.org/exhib/aab0080.htm","https://www.radiomuseum.org/tubes/tube_kt8c.html"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aab0080.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=KT8C","radiomuseum":"https://www.radiomuseum.org/tubes/tube_kt8c.html"},"raw_equivalents":["CV1079","VT79","KT807","KT8"],"equivalents":[],"similar":[{"type_number":"807","reason":"Electrically similar (same Pa_max, Va_max, Vs_max) but uses a UX5 base with different pin assignments — not pin-compatible","has_detail_page":true},{"type_number":"KT66","reason":"Related design basis — KT8C was derived from the KT66, but uses a B5 base with top-cap anode instead of the KT66 Octal base with internal anode","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"2","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Cathode","function_code":"k","notes":null},{"pin_number":"TC","function":"Anode (top cap)","function_code":"a","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":"1.27","numeric_value":"1.27","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Beam Tetrode","tube_type_key":"beam_tetrode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"600","numeric_value":"600","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"25","numeric_value":"25","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"600","numeric_value":"600","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"300","numeric_value":"300","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-100","numeric_value":"-100","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"85","numeric_value":"85","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"6.0","numeric_value":"6","unit":"mA","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"4.5","numeric_value":"4.5","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"38","numeric_value":"38","unit":"W","param_group":"output"},{"key":"freq","display_name":"Max Operating Frequency","value":"100","numeric_value":"100","unit":"MHz","param_group":"noise_rf"},{"key":null,"display_name":"Drive Power","value":"0.5","numeric_value":"0.5","unit":"W","param_group":null}]}],"synced_at":"2026-04-07T12:49:35.754Z"}