{"type_number":"ECH4","canonical_url":"https://tubeofile.com/tubes/ECH4","manufacturer":"Philips","tube_type_key":"triode_hexode","tube_type_display_name":"Triode-Hexode","base_name":"P8A","description":"Triode-hexode frequency converter with European side-contact (P8A) base, designed by Philips for use as combined oscillator and mixer in superheterodyne receivers. The triode section provides the local oscillator; the hexode section acts as mixer. Introduced January 1940, widely used in European radio receivers. The 'E' prefix denotes 6.3V heater, 'C' denotes frequency converter, 'H' denotes hexode section.","is_directly_heated":false,"completeness":"high","notes":["Uses the European side-contact P8A base — this is a spring-loaded contact system, not a pin system.","Predecessor was the ECH3; succeeded by the ECH21 (Rimlock) and ECH41.","ECH4N is a variant with different bulb shape but identical electrical characteristics.","Extensively used in European radio receivers from 1940-1950 with peak adoption around 1949.","The hexode section has three grids with the oscillator triode grid coupled to hexode grid 1."],"references":["https://tdsl.duncanamps.com/show.php?des=ECH4","https://www.radiomuseum.org/tubes/?tube=ECH4"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=ECH4","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ech4.html"},"raw_equivalents":["ECH4N"],"equivalents":[],"similar":[{"type_number":"ACH1n","reason":"Heater variant — same structure but different heater specification","has_detail_page":false},{"type_number":"ECH21","reason":"Successor triode-hexode converter with Rimlock base — different pin configuration","has_detail_page":false},{"type_number":"ECH41","reason":"Successor with Rimlock base (1941) — same functional design, different construction","has_detail_page":false},{"type_number":"ECH81","reason":"Later Noval successor — same triode-hexode concept but completely different base and pinout","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Hexode Plate","function_code":"ah","notes":null},{"pin_number":"2","function":"Hexode Screen Grid (g2)","function_code":"g2h","notes":null},{"pin_number":"3","function":"Triode Grid","function_code":"g1t","notes":null},{"pin_number":"4","function":"Triode Plate","function_code":"at","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"Cathode","function_code":"k","notes":null},{"pin_number":"7","function":"Hexode Signal Grid (g1h)","function_code":"g1h","notes":null},{"pin_number":"8","function":"Heater","function_code":"h","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":"0.35","numeric_value":"0.35","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (Oscillator)","tube_type_key":"small_signal_triode","specs":[{"key":"Va","display_name":"Anode Voltage (typical)","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"6","numeric_value":"6","unit":"mA","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"3.5","numeric_value":"3.5","unit":"mA/V","param_group":"typical_operating"}]},{"section_number":2,"section_label":"Hexode (Mixer)","tube_type_key":"hexode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Vg2_max","display_name":"Screen Voltage (max)","value":"150","numeric_value":"150","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"3.5","numeric_value":"3.5","unit":"mA","param_group":"typical_operating"},{"key":"Vg2","display_name":"Screen Voltage","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"mAg2","display_name":"Screen Current","value":"5","numeric_value":"5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"500000","numeric_value":"500000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.7","numeric_value":"0.7","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:39:59.225Z"}