{"type_number":"AL4","canonical_url":"https://tubeofile.com/tubes/AL4","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"P8A","description":"Output pentode with 4 V indirectly-heated cathode. Philips P8A side-contact base. The AL4 is the 4 V heater version of the EL3N. Designed for audio output stages in European AC mains receivers with 4 V heater transformers.","is_directly_heated":false,"completeness":"medium","notes":["For full data and characteristic curves, see type EL3N (per Philips datasheet).","The 'A' prefix in the Philips naming convention indicates a 4 V heater tube.","P8A side-contact base ('Sockel: P').","Heater: Vf = 4.0 V, If = 1.75 A, indirect, parallel supply."],"references":["https://frank.pocnet.net/sheets/030/a/AL4.pdf"],"source_urls":{"r_type":null,"tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_al4.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"EL11","reason":"Related power pentode — different characteristics","has_detail_page":true},{"type_number":"EL33","reason":"Octal-base equivalent — different base, not pin-compatible","has_detail_page":false},{"type_number":"EL3N","reason":"6.3 V heater version — electrically identical except heater, see EL3N for full data and curves","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Suppressor Grid (g3)","function_code":"g3","notes":null},{"pin_number":"2","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"3","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"4","function":"Cathode","function_code":"k","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"Heater","function_code":"h","notes":null},{"pin_number":"7","function":"Metallization","function_code":"ia","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"TC","function":"Anode (top cap)","function_code":"a","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4","numeric_value":"4","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.75","numeric_value":"1.75","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"power_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"9","numeric_value":"9","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-5.8","numeric_value":"-5.8","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"36","numeric_value":"36","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"5","numeric_value":"5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"50000","numeric_value":"50000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"9.5","numeric_value":"9.5","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"145","numeric_value":"145","unit":"Ω","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"3.8","numeric_value":"3.8","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"8000","numeric_value":"8000","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:35:35.847Z"}