{"type_number":"D3a","canonical_url":"https://tubeofile.com/tubes/D3a","manufacturer":"Telefunken","tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"Noval","description":"Special quality frame grid pentode for wideband amplification. Extremely high mutual conductance (35 mA/V) with tight tolerances. Guaranteed 10,000 hour life. Developed for telecommunications; widely used in audio as a high-gain voltage amplifier in pentode or triode connection.","is_directly_heated":false,"completeness":"high","notes":["Pin 1 and Pin 3 are both cathode connections (internally connected per datasheet note).","Also manufactured by Siemens, Valvo, and Philips with identical specifications.","Two triode connection methods documented: (a) g2 to anode, g3 to cathode (standard, lower rp); (b) g2 and g3 both to anode (higher Ca/g1 feedback capacitance). Section 2 uses method (a).","If Ck > 10 µF, a bias resistor ≥ 1 kΩ must be provided to protect grid 1 on switching after short interruption in operation.","Vhk_max is asymmetric: 60 V (heater negative of cathode) / 120 V (heater positive of cathode). The 120 V figure is recorded.","Maximum bulb temperature: 190 °C."],"references":["https://tube-data.com/sheets/128/d/D3a.pdf"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aaa1543.htm","tdsl":"http://tdsl.duncanamps.com/show.php?des=D3a","radiomuseum":"https://www.radiomuseum.org/tubes/tube_d3a.html"},"raw_equivalents":["7721","CV10804"],"equivalents":[],"similar":[{"type_number":"E280F","reason":"Same Noval pinout; lower gm (26 vs 35 mA/V) and lower μg2g1 (60 vs 80)","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Cathode","function_code":"k","notes":null},{"pin_number":"2","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"3","function":"Cathode (connected to pin 1)","function_code":"k","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":"Internal Connection","function_code":"ia","notes":null},{"pin_number":"7","function":"Anode","function_code":"a","notes":null},{"pin_number":"8","function":"Suppressor Grid (shield)","function_code":"g3","notes":null},{"pin_number":"9","function":"Screen Grid","function_code":"g2","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":"0.315","numeric_value":"0.315","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"ss_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"220","numeric_value":"220","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"180","numeric_value":"180","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"absolute_max"},{"key":"Ps_max","display_name":"Screen Dissipation (max)","value":"1.1","numeric_value":"1.1","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"33","numeric_value":"33","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"120","numeric_value":"120","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.5","numeric_value":"0.5","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"190","numeric_value":"190","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"160","numeric_value":"160","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-10","numeric_value":"-10","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"22","numeric_value":"22","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"6","numeric_value":"6","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"120000","numeric_value":"120000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"35","numeric_value":"35","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"400","numeric_value":"400","unit":"Ω","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"≤0.035","numeric_value":"0.035","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"6.8","numeric_value":"6.8","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"<0.050","numeric_value":null,"unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"10","numeric_value":"10","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"2.1","numeric_value":"2.1","unit":"pF","param_group":"capacitances"},{"key":"NF","display_name":"Noise Figure","value":"7","numeric_value":"7","unit":"dB","param_group":"noise_rf"},{"key":null,"display_name":"raeq","value":"150","numeric_value":"150","unit":"Ω","param_group":null},{"key":null,"display_name":"μg2g1","value":"80","numeric_value":"80","unit":"—","param_group":null}]},{"section_number":2,"section_label":"Triode Strapped","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"220","numeric_value":"220","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"33","numeric_value":"33","unit":"mA","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.5","numeric_value":"0.5","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"160","numeric_value":"160","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-10","numeric_value":"-10","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"24","numeric_value":"24","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1900","numeric_value":"1900","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"41","numeric_value":"41","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"77","numeric_value":"77","unit":"—","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"470","numeric_value":"470","unit":"Ω","param_group":"typical_operating"},{"key":null,"display_name":"raeq","value":"65","numeric_value":"65","unit":"Ω","param_group":null}]}],"synced_at":"2026-04-22T14:42:24.837Z"}