{"type_number":"EC8020","canonical_url":"https://tubeofile.com/tubes/EC8020","manufacturer":"Telefunken","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Noval","description":"Telefunken frame-grid triode designed for VHF/UHF amplifiers in grounded-grid configuration. Exceptionally high transconductance (60 mA/V) and low anode resistance (~917 Ohm) due to precision frame-grid construction with sub-100 micron cathode-grid spacing. Noval base, indirectly heated. Originally developed in the mid-1960s for PAL television UHF repeater stations. Highly sought after in high-end audio for phono preamplifiers and low-noise voltage gain stages.","is_directly_heated":false,"completeness":"high","notes":["Produced exclusively by Telefunken; no other manufacturer made genuine EC8020 tubes. First referenced July 1965 in Radio-Mentor #7.","Datasheet is marked 'Vorläufige technische Daten' (Tentative data). Telefunken document numbers 011164 (page 1) and 020165 (page 3).","Frame-grid construction: tungsten grid wire wound at extreme tension on a molybdenum frame, cathode-grid spacing under 100 microns.","Five grid pins (1, 3, 6, 7, 9) must all be connected to suppress UHF parasitic oscillation. Grid stopper resistors recommended at socket.","Designed for grounded-grid (common-grid) amplifier topology at VHF/UHF frequencies. In audio use, typically operated as common-cathode voltage amplifier.","Grid dissipation limit is only 30 mW; positive grid voltage limited to +1V. Max grid resistor 50 kOhm (cathode bias via Rk).","Heater-cathode voltage rating is +/-100V with max Rf/k of 20 kOhm, permitting elevated heater potential for hum reduction in audio applications.","Guaranteed life of 10,000 hours averaged over 100 tubes, provided heater voltage is held within +/-5% of 6.3V."],"references":["https://frank.pocnet.net/sheets/117/e/EC8020.pdf","https://www.phaedrus-audio.com/super_gm.htm"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=EC8020","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ec8020.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"3A/167M","reason":"STC high-gm triode electrically similar to WE437A; uses Loctal base — not pin-compatible","has_detail_page":true},{"type_number":"437A","reason":"Western Electric high-gm triode (gm=46 mA/V, ra=900 Ohm); similar electrical class but uses Magnoval base — not pin-compatible","has_detail_page":true},{"type_number":"6S45P","reason":"Soviet frame-grid triode (gm=45 mA/V, ra=1156 Ohm); same Noval base but different pinout — not drop-in compatible","has_detail_page":true},{"type_number":"EC8010","reason":"Philips/Mullard high-gm frame-grid triode (gm=28 mA/V, Pa_max=4.2W); same Noval base but different pinout and lower dissipation","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Grid","function_code":"g1","notes":null},{"pin_number":"2","function":"Cathode","function_code":"k","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","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":"Grid","function_code":"g1","notes":null},{"pin_number":"7","function":"Grid","function_code":"g1","notes":null},{"pin_number":"8","function":"Anode","function_code":"a","notes":null},{"pin_number":"9","function":"Grid","function_code":"g1","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":"0.28","numeric_value":"0.28","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"8","numeric_value":"8","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"70","numeric_value":"70","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":"0.05","numeric_value":"0.05","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"200","numeric_value":"200","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-2.5","numeric_value":"-2.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"40","numeric_value":"40","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"917","numeric_value":"917","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"60","numeric_value":"60","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"55","numeric_value":"55","unit":"—","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"62","numeric_value":"62","unit":"Ω","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"3.3","numeric_value":"3.3","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"12","numeric_value":"12","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"0.23","numeric_value":"0.23","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:38:19.491Z"}