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A1178

 
    
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The A1178 is a low noise audio triode designed for microphone pre-amplifiers. The base is Ct4.
The Osram paper label.
The Ct4 base.
The grid connects to the top cap and there looks to be a screen above the top mica.
The grid has side shields so that only the central section is active. The white coated cathode can be seen in the centre.
The classic envelope is 30 mm in diameter, and excluding the Ct4 base pins is 80 mm tall.
Reference: 1043. Type A1178 was first introduced in 1939. See also 1939 adverts.

 

Pin Connections
Ct4
1
2
3
4
tc
a
k
h
h
g1

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
4.0
0.25
150
-
-
9,000
2.8
Updated May 08, 2022.
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