two tube regen

A Two Tube Regenerative Set

This is a little battery broadcast set using two # 30 tubes. The first tube acts as a regenerative detector with a variable coupling feedback coil. The second tube is an audio amplifier driving headphones.

Again, I used solid Mahogany for the base and front panel with no stain, just the natural wood showing through the several coats of lacquer. I wanted to add a personal touch to the panel so I made two cutouts of a hummingbird in the upper corners. The left knob adjusts the regeneration and the right knob adjusts the filament voltage.

As you can see, the circuit is very simple. The B+ is 22 to 45 volts and the A+ is two "D" cells in series. You sometimes see this circuit with the "A" supply reversed. I couldn't tell any difference in operation. The transformer is an All-American 5 to 1 ratio which helps with the over-all gain. The headphones are vintage 2000 ohm.

Back view showing the nice globe shaped # 30's and the vintage binding posts with markings.

Left side view showing the coil assembly. It was in bad shape when I acquired it. I had to completely replace the green silk wire on all three windings. Also, notice the variable capacitor. It is another NOS AMSCO straight line frequency unit from my collection.

Top view showing the transformer and filament rheostat. You can't see much of the wiring, but I used # 16 solid tinned wire with black lacquered cloth spaghetti tubing I purchased from Antique Electronic Supply.