{"type_number":"EL3","canonical_url":"https://tubeofile.com/tubes/EL3","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"P8A","description":"Output pentode for audio amplifiers; indirectly heated. Original Philips 'red series' design from 1936 with P8A side-contact base and top-cap anode. 6.3 V version of the AL3. Superseded by the EL3N (1938) which reduced heater current from 1.2 A to 0.9 A via improved profile-cathode design.","is_directly_heated":false,"completeness":"high","notes":["The EL3 is the original 1936 design with 1.2 A heater current. The EL3N successor (1938) reduced this to 0.9 A using a more efficient profile-cathode while maintaining the same electrical characteristics.","Only specimens with straight cylindrical bulbs are authentic EL3; dome-bulb variants are actually EL3Ns.","Anode connection is via top cap. The P8A side-contact base carries heater, cathode, grids, and metallization.","Cathode-bias only — fixed bias is prohibited per the Philips datasheet.","Screen dissipation: max 1.2 W at zero signal, max 2.5 W at maximum output power.","Class A SE: Va = 250 V, Vg2 = 250 V, Rk = 150 Ω, rl = 7 kΩ delivers 4.5 W.","Class AB push-pull (2x): Va = 250 V, Vg2 = 250 V, Rk = 140 Ω, Raa = 10 kΩ delivers 8.2 W."],"references":["https://tdsl.duncanamps.com/show.php?des=EL3","https://www.radiomuseum.org/tubes/?tube=EL3"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=EL3","radiomuseum":"https://www.radiomuseum.org/tubes/tube_el3.html"},"raw_equivalents":["3REP6","TEL3","VEL3"],"equivalents":[],"similar":[{"type_number":"AL3","reason":"4 V heater version — not interchangeable without heater modification","has_detail_page":true},{"type_number":"EL11","reason":"Electrically identical but Y8A steel base — not pin-compatible with P8A side-contact sockets","has_detail_page":true},{"type_number":"EL3/375","reason":"Factory-selected variant rated to 375 V — same P8A base, same EL3N heater current (0.9 A)","has_detail_page":true},{"type_number":"EL3G","reason":"Glass envelope variant with Octal base — not pin-compatible with P8A sockets","has_detail_page":true},{"type_number":"EL3N","reason":"Improved successor with reduced heater current (0.9 A vs 1.2 A) — same P8A base, electrically near-identical","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"2","function":"Cathode","function_code":"k","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"6","function":"Metallization (external shield)","function_code":"ia","notes":null},{"pin_number":"7","function":"Suppressor Grid (internally connected to cathode)","function_code":"g3","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":"6.3","numeric_value":"6.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.2","numeric_value":"1.2","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":"275","numeric_value":"275","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":"Ps_max","display_name":"Screen Dissipation (max)","value":"2.5","numeric_value":"2.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"55","numeric_value":"55","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"100","numeric_value":"100","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"1","numeric_value":"1","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":"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":"-6","numeric_value":"-6","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":"4","numeric_value":"4","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","numeric_value":"9","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"150","numeric_value":"150","unit":"Ω","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"7000","numeric_value":"7000","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:43:55.343Z"}