{"type_number":"30","canonical_url":"https://tubeofile.com/tubes/30","manufacturer":"RCA","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"UX4","description":"Directly heated triode for detector and audio amplifier service in battery-operated receivers. 2V/0.06A filament for dry-cell operation. Introduced in the early 1930s as a lower-power replacement for the 01A in portable and battery sets. UX4 base (4-pin), glass bulb (ST-12).","is_directly_heated":true,"completeness":"medium","notes":["DHT tube: the filament serves as the cathode; there is no heater-cathode isolation.","Designed for 2V dry-cell (battery) filament supply at 0.06A — extremely low filament power for portable sets.","TDSL lists operating data at Va=135V: Vg=-9V, Ia=3mA, ra=10300 Ohm, gm=0.9 mA/V. GE Essential Characteristics lists the same ra and gm at Va=180V with Vg=-13.5V, Ia=3.1mA.","Radiomuseum lists typical operation at Va=90V: Ia=2.5mA, Vg=-4.5V, gm=0.85 mA/V.","No Pa_max or Rg_max is specified on known datasheets."],"references":["https://frank.pocnet.net/sheets/121/3/30.pdf","https://frank.pocnet.net/sheets/127/3/30.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=30","radiomuseum":"https://www.radiomuseum.org/tubes/tube_30.html"},"raw_equivalents":["VT-27","VT-67","CV604"],"equivalents":[],"similar":[{"type_number":"01A","reason":"Same UX4 base DHT triode with similar mu (~8-9) but 5V/0.25A filament instead of 2V/0.06A; not interchangeable due to different filament supply","has_detail_page":true},{"type_number":"31","reason":"Companion 2V battery DHT with same filament voltage and UX4 base, but designed as power output tube with lower mu (~3.8) and higher current (12mA vs 3mA)","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Filament (f-)","function_code":"h","notes":null},{"pin_number":"2","function":"Plate (Anode)","function_code":"a","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament (f+)","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"2","numeric_value":"2","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.06","numeric_value":"0.06","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":"180","numeric_value":"180","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"180","numeric_value":"180","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-13.5","numeric_value":"-13.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"3.1","numeric_value":"3.1","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"10300","numeric_value":"10300","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.9","numeric_value":"0.9","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"9.3","numeric_value":"9.3","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"6","numeric_value":"6","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"3","numeric_value":"3","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"2","numeric_value":"2","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:08:44.755Z"}