RDL TX-AT1 Audio Isolation Transformer

Stan Java Lisco here with a quite crude schematic diagram showing a two-stage audio amplifier it's just a generic diagram various resistors and capacitors to provide the proper bias for these transistors the key here here's the input there's the output to NPN bipolar transistors how do we get the signal from one to the other well we can use what is known as capacitive coupling or we can use transformer coupling when you use transformer coupling as shown here and here is the transformer right there that transformer keeps the DC that makes this transistor work and the DC that makes that transistor work separate from each other it allows the alternating current audio signal to pass through from one transistor to the other but it prevents any DC interactions between these two stages in that sense it isolates the stages for DC so we might call that a DC isolation transformer even though no t