The production of a "local cannon" sound

The sound source was an existing radio cassette player. During the audition, it was found that when receiving FM stereo broadcast, the sound intensity and resolution were quite good, but
when playing tape, it was not humiliating, and there was distortion when the volume was turned up. The reason is analyzed: the dynamic range of FM stereo
broadcast is better than that of tape, and because the power supply of the front and rear stages of the power amplifier share a transformer , the power reserve is insufficient (25W). So I decided to add an additional transformer.
I found a zoow iron core and wound it into a transformer to supply power to the subsequent stages separately. The secondary wires were thicker to reduce the internal resistance. Later, I ordered the dynamic expander
in bulk from Guilin Wendi Technology Service Company by mail. After assembly, I tried it. When playing the tape, the effect was refreshing as described in the introduction of the dynamic expander : the entire sound field was extended, and the sound field was extended. The stereo level of high and midrange sounds is more obvious , and the bass is majestic and powerful. A piece of Strauss's "Vienna Wood Story Waltz" is so refreshing. Using a friend's MD911 laser record player as the sound source, the sound is even more beautiful.