{"type_number":"801A","canonical_url":"https://tubeofile.com/tubes/801A","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"UX4","description":"R-F Power Amplifier, A-F Power Amplifier, Modulator. Directly heated thoriated-tungsten filament triode designed for use as an RF power amplifier, audio-frequency power amplifier, and modulator.","is_directly_heated":true,"completeness":"high","notes":["Grid resistor must not exceed 0.5 MΩ with cathode bias or 0.1 MΩ with fixed bias.","Filament is thoriated tungsten and may be operated on AC or DC.","Originally designed for RF transmitter service; also widely used in audio SE amplifiers. The 801A is an uprated version of the earlier 801/10/10Y with improved plate dissipation (20W vs 12-16W).","Shares the same UX4 pinout as the 45, 2A3, and 300B directly-heated triodes.","Mounting position: vertical with base down, or horizontal with plane of plate vertical (on edge)."],"references":["https://frank.pocnet.net/sheets/049/8/801A.pdf","https://vinylsavor.blogspot.com/2014/04/tube-of-month-801a.html"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=801A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_801a.html"},"raw_equivalents":["801","VT62","CV621","202A","VT-25A"],"equivalents":[{"type_number":"VT-25A","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"10Y","reason":"Same basic structure but lower plate dissipation (12W vs 20W); not a direct replacement at full 801A ratings","has_detail_page":false},{"type_number":"205D","reason":"Similar directly heated triode with different ratings per RCA interchange","has_detail_page":false},{"type_number":"268A","reason":"Similar directly heated triode with different ratings per RCA interchange","has_detail_page":false},{"type_number":"310","reason":"Similar directly heated triode with different ratings per RCA interchange","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Filament +","function_code":"h","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament -","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"7.5","numeric_value":"7.5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.25","numeric_value":"1.25","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":"600","numeric_value":"600","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"20","numeric_value":"20","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"85","numeric_value":"85","unit":"mA","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.5","numeric_value":"0.5","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"425","numeric_value":"425","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-40","numeric_value":"-40","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"18","numeric_value":"18","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"5000","numeric_value":"5000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.6","numeric_value":"1.6","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"8","numeric_value":"8","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"1.6","numeric_value":"1.6","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"10200","numeric_value":"10200","unit":"Ω","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"6.0","numeric_value":"6","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"4.5","numeric_value":"4.5","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"1.5","numeric_value":"1.5","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T19:05:36.997Z"}