{"type_number":"12SX7","canonical_url":"https://tubeofile.com/tubes/12SX7","manufacturer":"RCA","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Octal","description":"Medium-mu twin triode amplifier designed for use with 12-cell storage battery supply. Each section is electrically independent except for the common heater. Useful as an audio amplifier, oscillator, converter, and multi-vibrator. Low B voltage rating (design center 26.5V).","is_directly_heated":false,"completeness":"high","notes":["Originally designed for battery-operated equipment using a 12-cell storage battery, hence the 12.6V heater and the unusually low design-center plate voltage of 26.5V. The tube works fine at normal B+ voltages up to 300–330V.","The Tung-Sol datasheet rates Pa_max at 2.75W and Va_max at 330V, while the RCA datasheet rates Pa_max at 2.5W and Va_max at 300V. The higher Tung-Sol ratings reflect compliance with EIA standard RS-239.","Same ratings and characteristics per unit as the 6SN7GT (except heater: 12.6V/0.3A vs 6.3V/0.6A). The curves under types 6J5 and 6SN7-GT also apply to each unit of the 12SX7-GT.","Heater voltage variants: 12SX7/12SN7 use 12.6V/0.3A heater, 6SN7 uses 6.3V/0.6A heater. Same pinout and pin functions on all variants."],"references":["https://frank.pocnet.net/sheets/049/1/12SX7GT.pdf","https://frank.pocnet.net/sheets/127/1/12SX7GT.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12SX7","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12sx7.html"},"raw_equivalents":["12SX7GT","12SN7GT","12SN7GTA","1633","CV3697","6SN7GT","6SN7GTA","6SN7GTB","6SN7W","VT-231"],"equivalents":[{"type_number":"1633","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"13D1","reason":"Electrically similar Noval double triode — different base (B9A vs Octal), not pin-compatible","has_detail_page":true},{"type_number":"6F8G","reason":"Twin triode with identical per-section electricals but top-cap grid on section 2 — different pin topology","has_detail_page":true},{"type_number":"6J5","reason":"Single triode with identical per-section electricals but completely different pinout — not a drop-in for a twin triode socket","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid (section 2)","function_code":"g1_2","notes":null},{"pin_number":"2","function":"Plate (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":"Plate (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":"12.6","numeric_value":"12.6","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.3","numeric_value":"0.3","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":"330","numeric_value":"330","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"2.75","numeric_value":"2.75","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","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":"Vg","display_name":"Grid 1 Bias Voltage","value":"-8","numeric_value":"-8","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":"7700","numeric_value":"7700","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.6","numeric_value":"2.6","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"20","numeric_value":"20","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"3.6","numeric_value":"3.6","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"3.0","numeric_value":"3","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"0.8","numeric_value":"0.8","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:05:49.190Z"}