If your player has a low-impedance headset (the type found on many handsets) you know you can not use them on many projects that require sensitive high-impedance headphones, such as experimental radios, intercoms, galena or crystal radios, etc.
The solution presented in this article solves this problem by converting its low impedance headphone into a high impedance headphone with high sensitivity and amplification.
It is a simple circuit powered by two small batteries that converts the low-impedance handset into a sensitive handset with 100 k ohms of input impedance. The circuit can even be used as a sensitive signal follower.
The low current required by the circuit guarantees excellent durability for the batteries used in the power supply. In figure 1 we have the complete diagram of the handset amplifier.
Since few components are used, we can mount them on a terminal bridge, as shown in figure 2.
The jack should be according to the plug of the handset to be used. The transistor accepts equivalents. The connection to the signal source can be done by claws or by a cable with a plug.
Material list
Q1 - BC548 or equivalent - general purpose NPN transistor
R1- 1 M ohms x 1/8 W - resistor - brown, black, green
C1-10uF - electrolytic capacitor
C2- 100 uF - electrolytic capacitor
G1, G2- Alligator Claws
S1 – On-Off switch
B1- 3 V- 2 small batteries
X1 - 8 to 100 ohms earphone
Miscellaneous: terminal strip, battery holder, mounting box, wires, soda, etc.
