{"type_number":"12B4A","canonical_url":"https://tubeofile.com/tubes/12B4A","manufacturer":null,"tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Noval","description":"Medium-mu single triode with indirectly heated cathode on Noval base. Designed for vertical deflection output and as a general-purpose audio driver. Features 12.6V/0.3A heater, low plate resistance (1030 ohm), and high transconductance (6.3 mA/V). Widely used in television vertical output stages and hi-fi audio circuits.","is_directly_heated":false,"completeness":"high","notes":["The 12B4A is an improved version of the 12B4 with tighter specifications. TDSL lists 12B4 as a different-rating substitute.","TDSL ratings: Va_max=550V, Pa_max=5.5W, Ik_max=30mA, Va_peak_max=1000V.","TDSL application data for frame (vertical) output: Va=150V, Vg=-17.5V, Ia=34mA, ra=1030 ohm, gm=6.3 mA/V.","Also available with 6.3V/0.6A heater — operated in series-string heater configurations in TV sets at 12.6V.","Mu is approximately 6.5 (derived from gm x ra = 6.3 x 1030/1000 = 6.5).","Popular in DIY audio as a low-impedance line-stage driver or headphone amplifier due to its low ra and high gm."],"references":["https://frank.pocnet.net/sheets/127/1/12B4A.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12B4A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12b4a.html"},"raw_equivalents":["12B4"],"equivalents":[],"similar":[{"type_number":"6C4","reason":"Medium-mu single triode on B7G base — similar amplifier/driver application but 6.3V heater, higher ra (7700 ohm), and different base","has_detail_page":true},{"type_number":"6EM7","reason":"Dual dissimilar triode on Noval base with 6.3V heater — power section has similar low-ra characteristics, used in similar vertical output service","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"7","function":"Grid","function_code":"g1","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"9","function":"Cathode","function_code":"k","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"12.6","numeric_value":"12.6","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":"550","numeric_value":"550","unit":"V","param_group":"absolute_max"},{"key":"Va_peak_max","display_name":"Peak Anode Voltage (max)","value":"1000","numeric_value":"1000","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"5.5","numeric_value":"5.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"30","numeric_value":"30","unit":"mA","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":"-17.5","numeric_value":"-17.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"34","numeric_value":"34","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1030","numeric_value":"1030","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"6.3","numeric_value":"6.3","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"6.5","numeric_value":"6.5","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"4.8","numeric_value":"4.8","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"5.0","numeric_value":"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":"2026-04-07T12:04:35.922Z"}