{"type_number":"6B4G","canonical_url":"https://tubeofile.com/tubes/6B4G","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"Octal","description":"Directly heated (coated filament) power triode designed for single-ended Class A audio output service. Electrically equivalent to the 2A3 and 6A3 but on an Octal base with 6.3V/1.0A filament. Ratings and characteristics are similar to those of the 2A3 and 6A3.","is_directly_heated":true,"completeness":"high","notes":["The 6B4G is the Octal-base version of the 2A3 with a 6.3V coated filament instead of the 2A3's 2.5V thoriated tungsten filament. This makes it more practical for standard 6.3V heater supplies.","Class A1 single-ended: 3.2W output at 250V plate, -45V grid, 60mA, into 2500Ω load with 5% second harmonic distortion.","Class AB1 push-pull (two tubes): 15W output at 325V plate, fixed bias -68V, into 3000Ω effective plate-to-plate load with 2.5% THD.","Grid circuit resistance max: 0.05 MΩ with fixed bias, 0.5 MΩ with self (cathode) bias.","The 6S4S (6С4С) is the Soviet equivalent with the same Octal base and 6.3V filament.","Brans Vademecum lists the 2A3, 2A3W, 6A3, AC042, and ZA3W as equivalents in the power triode Class B table (IIIb)."],"references":["https://frank.pocnet.net/sheets/127/6/6B4G.pdf","https://tdsl.duncanamps.com/show.php?des=6B4G"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=6B4G","radiomuseum":"https://www.radiomuseum.org/tubes/tube_6b4g.html"},"raw_equivalents":["6S4S","CV1831"],"equivalents":[],"similar":[{"type_number":"2A3","reason":"Same electrical characteristics (mu=4.2, 3.5W SE) but UX4 base and 2.5V/2.5A filament — different base and filament voltage","has_detail_page":true},{"type_number":"2A3W","reason":"Ruggedized 2A3 on UX4 base — same electricals but different base and filament","has_detail_page":false},{"type_number":"300B","reason":"Directly heated power triode, higher power (8W SE), different base and filament (5V/1.2A)","has_detail_page":true},{"type_number":"45","reason":"Directly heated power triode on UX4 base, lower power (1.6W SE), 2.5V/1.5A filament","has_detail_page":true},{"type_number":"6A3","reason":"Same electrical characteristics and 6.3V filament but UX4 base — not Octal compatible","has_detail_page":false},{"type_number":"6A5G","reason":"Single-plate 2A3 variant on Octal base — similar application but verify electrical compatibility","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Filament","function_code":"h","notes":null},{"pin_number":"3","function":"Plate","function_code":"a","notes":null},{"pin_number":"4","function":"Grid","function_code":"g1","notes":null},{"pin_number":"5","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"6","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"7","function":"Filament","function_code":"h","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","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":"1.0","numeric_value":"1","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"power_triode","specs":[{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"15","numeric_value":"15","unit":"W","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.05","numeric_value":"0.05","unit":"MΩ","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":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-45","numeric_value":"-45","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"60","numeric_value":"60","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"800","numeric_value":"800","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"5.25","numeric_value":"5.25","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"4.2","numeric_value":"4.2","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"3.2","numeric_value":"3.2","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"2500","numeric_value":"2500","unit":"Ω","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"16","numeric_value":"16","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"7","numeric_value":"7","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"5","numeric_value":"5","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:17:16.540Z"}