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ID = 3654
United States of America (USA)
Developer: RCA (RCA Victor Co. Inc.); New York (NY) 
Tube type:  Triode, vacuum   Universal 
Identical to 01A = 201A = D401A = 201 = ER201A = C509A = C509 = 301A = VT-30 = DC201A_UV = CV750 = 401A_UX = LS201A = FX201A = CX201A = X-201A = 4600 = RH201A = MX201A = HF201A_perfectron = KD01A = TSX201A = LB-201A = P201A = NU-01A = SX01A = SLX201A = PA201A = T01A = D201A = G&R201A = NX-201A = ZP201A = BG-201A = RayX-201A = D-201A = EX201A = Z201A = S01A
Similar Tubes
Other shape (e.g. bulb type):
  AX201A ; DX-235 ; EX-1A ; M01A ; UX-201-A_Japan ; UX201A
Normally replaceable-slightly different:
  01AA ; 38001 ; AX ; A_UX-base ; C-201A
Other base:
First year 1925 -- Other type before this -same/similar characteristics - see exchange. as UX201A but "Dome form" 01A in 1932
Predecessor Tubes UX201A   CX301A   GX201A  

Base UX-Base (4 Pins (2 thick, USA 1924, UX) (Codex=Bo)
Was used by Radio/TV-reception etc.
Filament Vf 5 Volts / If 0.25 Ampere / Direct / Battery =

Tyne page 308ff brings the details of history. Here the main points only: The first tubes RCA is marketing in 1920 are the detector tube UV200 with argon gas filling and the UV201 Amplifier. Manufacturer was General Electric (GE).

In 1922 GE replaces the UV201 with the UV201A, having now a thorium filament.

In 1925 this tube comes with a new base and standardised construction (of 1923) for neutrodyne apparatus and is then called UX201A. Cunningham is naming the tube CX301A.

By having the tube with a shoulder type glass envelope (dome type) in 1932 the designation is changed to 01A.

The 01-A or 01A as we write it is a storage battery triode used as detector or amplifier.

Operating as grid-resistor detector are: plate volts = max. 45, grid resistor 2 or 3 megohms, grid capacitor 250 pF and grid return to filament plus. As biased detector, type 01-A has plate volts of 135 max, bias fo approx. - 13,5 volts. As amplifier, it has plate volts of 135 max., bias of - 9 volts. Filament takes 5 volts with 0.25 amperes.

Text in other languages (may differ)
Dimensions (WHD)
incl. pins / tip
x 108 x 45 mm / x 4.25 x 1.77 inch
Weight 46 g / 1.62 oz
Tube prices 6 Tube prices (visible for members only)
Information source Essential Characteristics, GE 1973   
Taschenbuch zum Röhren-Codex 1948/49   
Babani, International Radio Tube Encyclopaedia

01A: MK-Röhrentabelle
Daniel Consales

s_217_g.gif 01A: W.Sprick: Austausch-Röhren-Lexikon 1947
Günther Stabe † 19.8.20

More ...

Just Qvigstad
01A: Sylvania Rec. Tubes Manual 1944
Daniel Consales

More ...
Usage in Models 3= 1925? ; 2= 1926? ; 1= 1926 ; 7= 1927? ; 2= 1927 ; 3= 1932?? ; 4= 1932? ; 8= 1932 ; 2= 1933?? ; 1= 1934?? ; 4= 1934 ; 1= 1935?? ; 1= 1935? ; 2= 1935 ; 2= 1936 ; 1= 1937?? ; 2= 1937 ; 1= 1940?? ; 2= 1940?

Quantity of Models at with this tube (valve, valves, valvola, valvole, válvula, lampe):49

Collection of




Variant in blue made by Arcturus USA.Same electrical characteristics of base model 01A, same pin arrangement and UX base.

Metal coated cylindrical glass version. Complete name: M01A. The letter "M" appears only on the boxes and enclosed paperwork, not on the tubes. Please klick here: M01A

Forum contributions about this tube
Threads: 1 | Posts: 1
Hits: 5612     Replies: 0
Short Illustrated History of the 01A (01A)
Konrad Birkner † 12.08.2014
  1 RCA

UV200 (Argon-gas filled at 0,05 mm Hg), and UV201 (vakuum) had brass base and tip; 1 amp @ 5 volt filament.

  Marketed by RCA. announced in November 1920 and advertised for sale in December 1920.
UV201A (vakuum) from October 1922, brass base, tipped. 
Filament took .25 anp @ 5 volt.
From mid 1924 on bakelite base, no more tip.
     both types UV201A


The new UX based tubes were throughout untipped and used a Bakelite base.

(vakuum) from August 1925; .25 amp @ 5volt, and
UX200A (caesium vapor) from April 1926; .25 amp @ 5 volt.

 UX200A       UX201A

distributed the same tubes types but under different denomination: C in place of UV  and CX instead of UX. Furthermore the 20x numbers became 30x. 
Consequently C300 = UV200  und  CX301 = UX201.

  Cunningham CX301
Soon an abbreviated name came into everydays use for the practically identical tubes having different names. They were simply called the 01  or '01. That can be found even printed on schematics etc. It was kind of a generic name.
Officially this name 01A appeared around 1932 for the shoulder or dome type glass envelopes.

  '01A with "shoulder" (dome type)

RCA had initially no tube manufacturing. They marketed tubes made by Westinghouse or General Electric as a distributor, but under their own brand "Radiotron". Cunningham was also involved in that nearly monopolistic business.
In 1930 RCA eventually established the "RCA Radiotron, Inc." as their own manufacturing subsidiary.

since the 01A is a perfect functional replacement for a.m. tubes, it is not really an error if it is called for a radio before 1932. But anyway we should always try to state the coincident tube types for the models.

Ref.: Saga of the Vacuum Tube
Photos: Authors collection
End of forum contributions about this tube

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