Ninety years ago this month, these three Soviet radio experimenters were putting together what appears to be an audio amplifier, following the plans contained in the June 1929 issue of Радиолюбитель (Radio amateur) magazine.  Apparently, they’re either small experimenters, or they’re using a very large tube.

Unfortunately, the scan is rather low quality, but the word усилитель (amplifier) appears in the title.  There are headphones hooked to the plate, so it must be an audio amplifier.  The circuit is simple, with the only control being the rheostat on the front panel to control the filament voltage.  It’s likely that the input of the amp would be hooked to a crystal set, with the tube amplifying the volume to a more listenable level.

Not to be outdone, these Soviet girls are shown in the same magazine putting the finishing touches on another electronic project.