{"type_number":"417A","canonical_url":"https://tubeofile.com/tubes/417A","manufacturer":"Western Electric","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Noval","description":"Medium-mu triode for use in high-gain audio preamplifiers and telecommunications equipment. Known for very low plate resistance and high transconductance.","is_directly_heated":false,"completeness":"high","notes":["Originally designed by Western Electric for telephone repeater amplifier service.","The 5842 is the RETMA/JAN designation for the same tube as the 417A.","Single triode despite the Noval base; pins 4, 5, 7, and 8 are all connected to the grid for low inductance.","Very low plate resistance (1700 ohms) and high transconductance (25 mA/V) make it suitable as a low-impedance driver.","Widely used in high-end audio preamplifiers and microphone preamps.","Coated unipotential cathode; may be operated in any position.","RCA datasheet dated March 1962."],"references":["https://frank.pocnet.net/sheets/049/5/5842.pdf"],"source_urls":{"r_type":"https://www.radiomuseum.org/tubes/tube_417a.html","tdsl":"https://tdsl.duncanamps.com/show.php?des=417A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_417a.html"},"raw_equivalents":["5842","WE417A","1547"],"equivalents":[],"similar":[{"type_number":"12AT7","reason":"Noval medium-mu triode (mu=60) but twin triode with higher ra (10900 ohms); different pinout","has_detail_page":true},{"type_number":"6AK5","reason":"Noval miniature tube used in similar telecom/instrumentation applications but is a pentode","has_detail_page":true},{"type_number":"6C45Pi","reason":"Single noval triode with very high gm and low ra; similar high-current low-impedance design philosophy","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Plate","function_code":"a","notes":null},{"pin_number":"2","function":"No Internal Connection","function_code":"nc","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Grid","function_code":"g1","notes":null},{"pin_number":"5","function":"Grid","function_code":"g1","notes":null},{"pin_number":"6","function":"Cathode","function_code":"k","notes":null},{"pin_number":"7","function":"Grid","function_code":"g1","notes":null},{"pin_number":"8","function":"Grid","function_code":"g1","notes":null},{"pin_number":"9","function":"Heater","function_code":"h","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":"0.3","numeric_value":"0.3","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"200","numeric_value":"200","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"38","numeric_value":"38","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"55","numeric_value":"55","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-9","numeric_value":"-9","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"25","numeric_value":"25","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":"25","numeric_value":"25","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"43","numeric_value":"43","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"1.8","numeric_value":"1.8","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"9","numeric_value":"9","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"0.55","numeric_value":"0.55","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:09:44.477Z"}