{"type_number":"350A","canonical_url":"https://tubeofile.com/tubes/350A","manufacturer":"Western Electric","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"UX4","description":"Western Electric power triode; directly heated thoriated tungsten filament. Originally designed for telephone repeater and audio amplifier service. Known for linear characteristics and smooth sound in single-ended amplifier applications.","is_directly_heated":true,"completeness":"high","notes":["The 350A was designed by Western Electric for use in telephone repeaters and public address systems. The 350B is a later version with improved construction.","Directly heated thoriated tungsten filament with 5V/2A rating. Medium-4 pin (UX4) base."],"references":["https://tdsl.duncanamps.com/show.php?des=350A"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=350A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_350a.html"},"raw_equivalents":["350B","WE350A","WE350B"],"equivalents":[{"type_number":"350B","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"2A3","reason":"Similar power triode with UX4 base but different operating point — 2A3 has lower mu (4.2 vs 3.8) and different filament voltage (2.5V vs 5V)","has_detail_page":true},{"type_number":"300B","reason":"Higher-powered WE triode with same UX4 base but higher plate dissipation (36W vs 20W) and different operating conditions","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Filament","function_code":"f","notes":null},{"pin_number":"2","function":"Grid","function_code":"g","notes":null},{"pin_number":"3","function":"Anode","function_code":"a","notes":null},{"pin_number":"4","function":"Filament","function_code":"f","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"5","numeric_value":"5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"2","numeric_value":"2","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":"400","numeric_value":"400","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":"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":"-51","numeric_value":"-51","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":"1400","numeric_value":"1400","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.7","numeric_value":"2.7","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"3.8","numeric_value":"3.8","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:08:59.819Z"}