{"type_number":"4BZ8","canonical_url":"https://tubeofile.com/tubes/4BZ8","manufacturer":null,"tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Noval","description":"High-frequency twin triode with 4.2 V heater, designed for use as a cascode RF amplifier in television tuners. Noval (B9A) base. The two triode sections have different characteristics optimized for grounded-cathode (high-gm) and grounded-grid (high-mu) stages in a cascode configuration.","is_directly_heated":false,"completeness":"high","notes":["4.2 V / 600 mA heater — designed for parallel heater operation from a 4.2 V supply.","The two triode sections have dissimilar characteristics, optimized for cascode RF amplifier operation.","GE Essential Characteristics lists: Pa_max 2.2 W, Va_max 250 V, gm 6200 µmhos, ra 5300 Ω, mu ~33."],"references":["https://tdsl.duncanamps.com/show.php?des=4BZ8","https://www.radiomuseum.org/tubes/?tube=4BZ8"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=4BZ8","radiomuseum":"https://www.radiomuseum.org/tubes/tube_4bz8.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"6BK7","reason":"Brans lists as equivalent — verify pin compatibility","has_detail_page":true},{"type_number":"6BZ8","reason":"Identical electrically but with 6.3 V heater — different heater voltage","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Anode (Unit 1)","function_code":"a1","notes":null},{"pin_number":"2","function":"Grid (Unit 1)","function_code":"g1","notes":null},{"pin_number":"3","function":"Cathode (Unit 1)","function_code":"k1","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":"Anode (Unit 2)","function_code":"a2","notes":null},{"pin_number":"7","function":"Grid (Unit 2)","function_code":"g2","notes":null},{"pin_number":"8","function":"Cathode (Unit 2)","function_code":"k2","notes":null},{"pin_number":"9","function":"Internal Shield","function_code":"ia","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4.2","numeric_value":"4.2","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.6","numeric_value":"0.6","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (Unit 1, grounded-cathode)","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"2.2","numeric_value":"2.2","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"9","numeric_value":"9","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"5300","numeric_value":"5300","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"6.2","numeric_value":"6.2","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"33","numeric_value":"33","unit":"—","param_group":"typical_operating"}]},{"section_number":2,"section_label":"Triode (Unit 2, grounded-grid)","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"2.2","numeric_value":"2.2","unit":"W","param_group":"absolute_max"}]}],"synced_at":"2026-04-07T12:10:29.062Z"}