{"type_number":"845","canonical_url":"https://tubeofile.com/tubes/845","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"UX4","description":"Directly heated transmitting triode with thoriated tungsten filament and graphite anode. Developed by GE/RCA for Class A and Class B RF and audio-frequency power amplification. Jumbo 4-pin bayonet base (UX4). Widely used in high-end single-ended triode (SET) audio amplifiers.","is_directly_heated":true,"completeness":"high","notes":["DHT tube: the thoriated tungsten filament serves as the cathode; there is no heater-cathode isolation.","Graphite anode permits 100W plate dissipation (ICAS). CCS rating is 75W.","Class A1 amplifier at Va=1000V: Vg=-98V, Ia=65mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=5600 Ohm, Po=15W.","Class A1 amplifier at Va=1250V: Vg=-123V, Ia=80mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=6600 Ohm, Po=23W.","Class B audio push-pull (2 tubes): Va=1000V, max-signal Ia per tube=120mA, Po=50W; Va=1250V, max-signal Ia=150mA, Po=78W.","The 845W is the ruggedised variant with identical electrical characteristics."],"references":["https://frank.pocnet.net/sheets/049/8/845.pdf","https://www.radiomuseum.org/tubes/tube_845.html"],"source_urls":{"r_type":null,"tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_845.html"},"raw_equivalents":["UV845","VT-43","CV735","545","C845","38145","845W","R845","T845"],"equivalents":[],"similar":[{"type_number":"284A","reason":"WE transmitting triode listed as similar to 845 in RCA interchange guide; different filament and operating conditions","has_detail_page":false},{"type_number":"384D","reason":"WE transmitting triode listed as similar to 845 in RCA interchange guide; not pin-compatible","has_detail_page":false},{"type_number":"945","reason":"Transmitting triode listed as similar to 845 in RCA interchange guide","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Filament (f-)","function_code":"h","notes":null},{"pin_number":"2","function":"Plate (Anode)","function_code":"a","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament (f+)","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"10","numeric_value":"10","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"3.25","numeric_value":"3.25","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"1250","numeric_value":"1250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"100","numeric_value":"100","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"150","numeric_value":"150","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"1000","numeric_value":"1000","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-98","numeric_value":"-98","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"65","numeric_value":"65","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1700","numeric_value":"1700","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"3.1","numeric_value":"3.1","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"5.3","numeric_value":"5.3","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"15","numeric_value":"15","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"5600","numeric_value":"5600","unit":"Ω","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"6.5","numeric_value":"6.5","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"7.5","numeric_value":"7.5","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"3.3","numeric_value":"3.3","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:34:03.459Z"}