{"type_number":"CV4086","canonical_url":"https://tubeofile.com/tubes/CV4086","manufacturer":"Mullard","tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"Noval","description":"British military (CV) designation for the EF86/6267 — low-noise sharp-cutoff pentode in Noval envelope. Designed for high-gain, low-noise audio preamplifier stages. The CV4086 is the premium military-grade version with tighter specifications and lower microphonics.","is_directly_heated":false,"completeness":"medium","notes":["The CV4086 is the British military specification version of the EF86 with tighter parameter tolerances, improved microphonic performance, and ruggedised construction.","The EF86 is one of the most popular audio preamplifier pentodes, widely used in guitar amplifiers (Vox AC30) and hi-fi equipment.","Typical operation at Va=250V, Vg2=140V, Vg=-2V: Ia=3mA, Ig2=0.6mA, gm=1800 umhos, Rp=2500kΩ, mu=4500. Extremely high mu and plate resistance characteristic of a low-noise audio pentode."],"references":["https://tdsl.duncanamps.com/show.php?des=EF86"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=EF86","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ef86.html"},"raw_equivalents":["EF86","6267","Z729","M8195","CV4085","8225"],"equivalents":[{"type_number":"EF86","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"5879","reason":"Similar low-noise pentode but different pinout and slightly different characteristics — not pin-compatible","has_detail_page":true},{"type_number":"6AU6","reason":"Similar sharp-cutoff pentode on Noval base but higher noise, different pinout","has_detail_page":false},{"type_number":"EF806S","reason":"Telefunken premium version of EF86 — same electricals, even tighter specs and lower microphonics","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Internal shield","function_code":"shell","notes":null},{"pin_number":"2","function":"Anode","function_code":"a","notes":null},{"pin_number":"3","function":"Grid 3 (Suppressor)","function_code":"g3","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 2 (Screen)","function_code":"g2","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","notes":null},{"pin_number":"8","function":"Cathode (connected to pin 7)","function_code":"k","notes":null},{"pin_number":"9","function":"Grid 1 (Control 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":"0.2","numeric_value":"0.2","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":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"1","numeric_value":"1","unit":"W","param_group":"absolute_max"},{"key":"Vg2_max","display_name":"Screen Voltage (max)","value":"200","numeric_value":"200","unit":"V","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":"-2","numeric_value":"-2","unit":"V","param_group":"typical_operating"},{"key":"Vg2","display_name":"Screen Voltage","value":"140","numeric_value":"140","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"3","numeric_value":"3","unit":"mA","param_group":"typical_operating"},{"key":"mAg2","display_name":"Screen Current","value":"0.6","numeric_value":"0.6","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"2500000","numeric_value":"2500000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.8","numeric_value":"1.8","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"4500","numeric_value":"4500","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:37:11.588Z"}