{"type_number":"46","canonical_url":"https://tubeofile.com/tubes/46","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"UX5","description":"Dual-grid directly heated power amplifier tube. Can operate as Class A triode (both grids tied together), Class B triode, or Class B with grids tied (tetrode-connected). Introduced by RCA circa 1931 on a UX5 (UY) base with 2.5V/1.75A filament.","is_directly_heated":true,"completeness":"low","notes":["MIL-HDBK-213A lists as VT-63 with service classification 'Class B amplifier'.","The 46 has two grids; for Class A triode operation both grids are tied together to form a single control element.","Class B push-pull operation with grids tied yields up to 20W output at 400V (per pair).","TDSL lists CV2531 as a close or identical substitute.","Radiomuseum classifies as 'Double Grid Power Amplifier' (ID 2835).","Commonly found in 1930s radio receivers and early audio amplifiers."],"references":["https://frank.pocnet.net/sheets/127/4/46.pdf"],"source_urls":{"r_type":"https://www.radiomuseum.org/tubes/tube_46.html","tdsl":"https://tdsl.duncanamps.com/show.php?des=46","radiomuseum":"https://www.radiomuseum.org/tubes/tube_46.html"},"raw_equivalents":["VT-63","CV2531"],"equivalents":[],"similar":[{"type_number":"2A3","reason":"Directly heated power triode on UX4 base, same 2.5V filament — higher power (3.5W SE) and lower ra","has_detail_page":true},{"type_number":"45","reason":"Directly heated power triode on UX4 base, same 2.5V filament — similar Class A power (1.6W) but true triode with no second grid","has_detail_page":true},{"type_number":"47","reason":"Directly heated power pentode on UX5 base, same 2.5V filament — pentode rather than dual-grid design","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Grid 1 (Control Grid)","function_code":"g1","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"Grid 2","function_code":"g2","notes":null},{"pin_number":"4","function":"Filament (f+)","function_code":"h","notes":null},{"pin_number":"5","function":"Filament (f-)","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"2.5","numeric_value":"2.5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.75","numeric_value":"1.75","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (Class A, grids tied)","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"10","numeric_value":"10","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-33","numeric_value":"-33","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"22","numeric_value":"22","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"2380","numeric_value":"2380","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.35","numeric_value":"2.35","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"5.6","numeric_value":"5.6","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"1.25","numeric_value":"1.25","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"6400","numeric_value":"6400","unit":"Ω","param_group":"output"}]},{"section_number":2,"section_label":"Class B push-pull (grids tied, per pair at 300V)","tube_type_key":"power_triode","specs":[{"key":"Va","display_name":"Anode Voltage (typical)","value":"300","numeric_value":"300","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"0","numeric_value":"0","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"8","numeric_value":"8","unit":"mA","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"16","numeric_value":"16","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"5200","numeric_value":"5200","unit":"Ω","param_group":"output"}]},{"section_number":3,"section_label":"Class B push-pull (grids tied, per pair at 400V)","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"400","numeric_value":"400","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"400","numeric_value":"400","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"0","numeric_value":"0","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"12","numeric_value":"12","unit":"mA","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"20","numeric_value":"20","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"5800","numeric_value":"5800","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:10:05.626Z"}