At your risk. Take all safety precautions. Any voltage or current can be dangerous. A suitable series fuse should always be connected with a battery.
It is just 2 one transistor stages.
A BC109 collector direct feeding an ACY21 pnp transistor base.
The ACY21 output stage is resistance capacitance coupled to an output transformer.
The simplest amplifier again.
The amplifier miracle.
In more detail:
There are 3 rails. +20V, 0V or ground and -20V.
Input terminal is connected to a 150KΩ resistor. Other side of resistor to ground line above the transistor. Ground line is above both transistors.
Music signal is coupled to base of first transistor though a 2.2μF non electrolytic capacitor.
Ground or 0V rail on top of both transistors is connected to a 180KΩ base bias resistor whose other side is naturally connected to BC109 base.
Base of said front end transistor is also connected to a 130KΩ resistor whose other side is connected to -20V. The potential at base should be around -11.6V.
Collector of BC109 is connected through a load resistor of 150KΩ to +20V. (It is amazing how these brilliant electronic engineers were designing transistor stages as if there were electron tube stages with high impeadnce, low current etc.
Emitter of BC109 at -12.3V potential is connected through a 820Ω resistor to -20V.
Collector of BC109 is directly connected to ACY21 base.
Emitter of said output transistor is directly connected to 0V or ground rail.
Collector of said pnp transistor at -6.2V is connected to a 680Ω whose other side is connected to previously mentioned 820Ω emitter resistor of BC109.
The common point of these resistors is connected through 300Ω and a series 3300pF again to output transistor collector.
The common point of said 2 resistors is also connected to a 11K resistor which is connected to collector. Ie 11KΩ is in parallel with 680Ω.
Collector is connected though a 200μF to output terminal. Output terminal has the positive side of this electrolytic capacitor.
Output terminal is connected to 1.6KΩ. Said resistor is connected in series to a 2.2KΩ resistor. Said 2.2KΩ resistor is connected to 0V ground and has a 1500p and a 33K, both components in parallel with it in either side. The bottom side of the 2.2K, 33K resistors is connected to VU meter out terminal.
The output transformer is connected between 0V and output terminal.
See a previous post for the microphone Front end amplifier.
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