{"type_number":"6FD7","canonical_url":"https://tubeofile.com/tubes/6FD7","manufacturer":null,"tube_type_key":"compound","tube_type_display_name":"Compound (multi-section)","base_name":"Noval","description":"Dissimilar section double triode intended for the combined functions of vertical deflection oscillator (high-mu section) and vertical deflection amplifier (low-mu section). Features the T-9 bulb with integral wafer base fitting the standard 9-pin miniature socket.","is_directly_heated":false,"completeness":"high","notes":["10FD7 is identical to 6FD7 except for heater ratings (9.7V, 0.600A) and heater warm-up time. 13FD7 is identical except for heater ratings (13.0V, 0.450A).","Pin 2 and Pin 3 are both connected to the control grid of Section 2 (dual grid pins).","Maximum heater voltage range for the 6FD7 is 5.7-6.9V.","Originally designed for vertical deflection circuits in television receivers, but widely adopted by DIY audio designers (notably in Woo Audio WA6/WA6SE headphone amplifiers) as a combined driver/output tube in low-power amplifiers.","In stages operating with grid leak bias, an adequate cathode bias resistor or other suitable means is required to protect the tube in the absence of excitation."],"references":["https://frank.pocnet.net/sheets/201/6/6FD7.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=6FD7","radiomuseum":"https://www.radiomuseum.org/tubes/tube_6fd7.html"},"raw_equivalents":["10FD7","13FD7","1CFD7","6DA7"],"equivalents":[{"type_number":"6DA7","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"6DE7","reason":"Same 9HF pinout but Section 1 has much lower mu (17.5 vs 64). Section 2 is similar (mu=6, gm=6500). Not a drop-in replacement due to very different Section 1 characteristics.","has_detail_page":true},{"type_number":"6DR7","reason":"Same 9HF pinout and dissimilar double triode structure, but different electrical characteristics (Section 1: mu=68 vs 64, Pa_max=1W vs 1.5W; Section 2: gm=6500 vs 7500, Pa_max=7W vs 10W, Ih=0.9A vs 0.925A).","has_detail_page":true},{"type_number":"6EM7","reason":"Brans cross-lists in same group — Octal (8BD) vs Noval (9HF) base, different pin topology. Similar Section 1 (mu~64-68) but different Section 2 (ra=750 vs 800 ohms)","has_detail_page":true},{"type_number":"6EW7","reason":"Same 9HF pinout but Section 1 has much lower mu (17.5 vs 64). Uses T-9 bulb like 6FD7. Not a drop-in replacement due to very different Section 1 characteristics.","has_detail_page":true},{"type_number":"6FR7","reason":"Same 9HF pinout and dissimilar double triode structure, but different electrical characteristics. Sams Tube Substitution Handbook lists 6FD7 as substitute for 6FR7.","has_detail_page":true},{"type_number":"6GF7","reason":"Brans cross-lists — similar dissimilar twin triode with different characteristics","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Plate (Section 2)","function_code":"a2","notes":null},{"pin_number":"2","function":"Grid (Section 2)","function_code":"g1_2","notes":null},{"pin_number":"3","function":"Grid (Section 2)","function_code":"g1_2","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":"Plate (Section 1)","function_code":"a1","notes":null},{"pin_number":"7","function":"Grid (Section 1)","function_code":"g1_1","notes":null},{"pin_number":"8","function":"Cathode (Section 1)","function_code":"k1","notes":null},{"pin_number":"9","function":"Cathode (Section 2)","function_code":"k2","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":"0.925","numeric_value":"0.925","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"High-Mu 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":"1.5","numeric_value":"1.5","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":"200","numeric_value":"200","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"2.2","numeric_value":"2.2","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":"-3","numeric_value":"-3","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"1.4","numeric_value":"1.4","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"40000","numeric_value":"40000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1600","numeric_value":"1600","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"64","numeric_value":"64","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"4.5","numeric_value":"4.5","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"2.2","numeric_value":"2.2","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"0.4","numeric_value":"0.4","unit":"pF","param_group":"capacitances"}]},{"section_number":2,"section_label":"Low-Mu 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":"10","numeric_value":"10","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"50","numeric_value":"50","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"200","numeric_value":"200","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"2.2","numeric_value":"2.2","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-17.5","numeric_value":"-17.5","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":"800","numeric_value":"800","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"7500","numeric_value":"7500","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"6","numeric_value":"6","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"10","numeric_value":"10","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"6.5","numeric_value":"6.5","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"1.2","numeric_value":"1.2","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T19:03:48.581Z"}