This months tube is a quite uncommon directly heated triode, the 183/483.
This tube exisits junder two designations 183 and 483. The photo above shows a pair 483s branded Marvin. apparently this tube was only manufactured over a short peroid. While the RCA RC13 receiving tube databook does not list it yet, the RC14 lists it as 'replacement type' which means it is not recommended to design new equipment for it. RC15 lists it as discontinued type. So probably only a few radio sets used this tube.
The 183/483 is very similar to the 45. It has the same UX4 base. It has an amplification factor of 3 while the mu of the 45 is 3.5. The plate resistance is 1750 Ohm at a 250V plate voltage and 30mA current. This is very close to the values of the 45: 1600 Ohms at 34 mA. So it would work in a circuit designed for the 45. Only the filament voltage differs. It is 5V, double the value of the 45. Filament current is 1.25A, slight.ly lower than the 1.5A of the 45, but at double the filament voltage this is a significantly higher filament power requirement. Both can provide a power output of about 2sw in single ended. I have not found any databook which shows plate curves of this tube, so I measured it on a curve tracer:
Very linear as one would expect from a directly heated triode designed for audio purposes.
Construction is quite similar to that of the 45. Only the size of the bottle is bigger. The 183/483 comes in the same bottle as a 2A3. below a photo which shows a 2A3, 483 and 45 in comparison.
The filament follows the same 'M' shape as that of the 45, with two filament support on the top:
A very interesting tube, but since not many seem to be available not really recommended for DIY use. If you have some in your stash. It might make sense to adapt the filament voltage in a 45 amp to allow to use these. I do not have many 183/483 myself, so I'll probably never use them in an amp. Since little can be read about this type, I found it worthwhile to give it a place in the tube of the month series. Maybe somebody with some more information about this tube can provide details about it's history and background.