{"type_number":"4689K","canonical_url":"https://tubeofile.com/tubes/4689K","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"Octal","description":"Output pentode with 18 W anode dissipation; Philips Rimlock (B8A/K8A) base variant of the 4689. The 'K' suffix denotes the Rimlock base instead of the P8A side-contact base of the original 4689. Electrically equivalent to the EL5/AL5 family but in Octal envelope. Designed for high-power audio output stages.","is_directly_heated":false,"completeness":"medium","notes":["The 'K' suffix indicates the Rimlock/Octal (K8A) base variant. The original 4689 uses the P8A side-contact base. These are genuinely different tubes despite identical electrical characteristics.","Brans Vademecum lists equivalents: EL37, N43, PEN4VB, PM22A.","Anode connection via top cap for high-voltage isolation.","Pa_max = 18 W. Suitable for single-ended (approx. 8 W output) or push-pull operation (approx. 20 W)."],"references":["https://tdsl.duncanamps.com/show.php?des=4689K","https://www.radiomuseum.org/tubes/?tube=4689K"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=4689K","radiomuseum":"https://www.radiomuseum.org/tubes/tube_4689k.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"4689","reason":"Electrically identical but P8A side-contact base — different base, not pin-compatible","has_detail_page":true},{"type_number":"EL35","reason":"Electrically similar Octal-based pentode in the same family","has_detail_page":true},{"type_number":"EL37","reason":"Related Philips power pentode — similar but higher-spec Octal type","has_detail_page":true},{"type_number":"EL5","reason":"Electrically identical Philips designation with P8A base — not pin-compatible","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"4","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"5","function":"Cathode","function_code":"k","notes":null},{"pin_number":"6","function":"Suppressor Grid (internally connected to cathode)","function_code":"g3","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","function":"Metallization","function_code":"ia","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":"1.35","numeric_value":"1.35","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":"275","numeric_value":"275","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":"18","numeric_value":"18","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":"275","numeric_value":"275","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-7.5","numeric_value":"-7.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"58","numeric_value":"58","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"25000","numeric_value":"25000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"8.5","numeric_value":"8.5","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"8.8","numeric_value":"8.8","unit":"W","param_group":"output"}]}],"synced_at":"2026-04-07T12:10:18.258Z"}