{"type_number":"ECC33","canonical_url":"https://tubeofile.com/tubes/ECC33","manufacturer":"Mullard","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Octal","description":"High slope, low impedance double triode with low heater consumption, primarily intended for use in flip-flop, scaling and computer circuits. Also widely used as an audio voltage amplifier and phase splitter.","is_directly_heated":false,"completeness":"high","notes":["The heaters of the two cathodes are connected in series. When operating from a 6.3V supply, the heaters are in parallel internally; when from 12.6V, they are in series.","Despite sharing the same Octal base and pinout as the 6SN7, the ECC33 has significantly higher mu (35 vs 20) and gm (3.6 vs 2.6 mA/V), making direct substitution inadvisable without circuit recalculation. Many amplifier manufacturers list both as acceptable alternatives where the circuit can tolerate the difference.","Maximum anode voltage is only 300V — considerably lower than the 6SN7's 450V rating. Circuits designed around 6SN7 max ratings may over-stress an ECC33.","Mullard ECC33 tubes are highly sought after by audio enthusiasts, commanding premium prices. Production ran approximately 1949–1960s."],"references":["https://frank.pocnet.net/sheets/084/e/ECC33.pdf","https://frank.pocnet.net/sheets/129/e/ECC33.pdf","http://www.r-type.org/exhib/aaa0474.htm"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aaa0474.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=ECC33","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ecc33.html"},"raw_equivalents":["CV2821","CV3986","6SN7"],"equivalents":[{"type_number":"6SN7","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"ECC32","reason":"Same Octal base and same pinout, but electrically different: ECC32 has mu=20 and ra=5 kOhm. More similar to 6SN7 than to ECC33.","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid (section 2)","function_code":"g1_2","notes":null},{"pin_number":"2","function":"Anode (section 2)","function_code":"a2","notes":null},{"pin_number":"3","function":"Cathode (section 2)","function_code":"k2","notes":null},{"pin_number":"4","function":"Control Grid (section 1)","function_code":"g1_1","notes":null},{"pin_number":"5","function":"Anode (section 1)","function_code":"a1","notes":null},{"pin_number":"6","function":"Cathode (section 1)","function_code":"k1","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","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":"0.4","numeric_value":"0.4","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (each section)","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":"2.5","numeric_value":"2.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"20","numeric_value":"20","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":"1.5","numeric_value":"1.5","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":"Vg","display_name":"Grid 1 Bias Voltage","value":"-4","numeric_value":"-4","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"9","numeric_value":"9","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"9700","numeric_value":"9700","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"3.6","numeric_value":"3.6","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"35","numeric_value":"35","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"2.5","numeric_value":"2.5","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"3.5","numeric_value":"3.5","unit":"pF","param_group":"capacitances"},{"key":null,"display_name":"Rh-k max","value":"20","numeric_value":"20","unit":"kΩ","param_group":null},{"key":null,"display_name":"Vg(h) max","value":"550","numeric_value":"550","unit":"V","param_group":null},{"key":null,"display_name":"Anode-to-Anode Capacitance (Ca-a')","value":"0.75","numeric_value":"0.75","unit":"pF","param_group":null}]}],"synced_at":"2026-04-07T19:07:06.077Z"}