I want to make a power amplifier again. I took out a few domestic LM1875s from the bottom of the box and made a power amplifier. I took the time to open source them. . .
LM1875, TDA2030 are both available. It’s still the same shell and panel. . . . . .
About 10W*2, maximum.
Use XL6019 SPICE topology to generate positive and negative power supplies, PD or DC power supply.
The voltage of plus and minus 13.6V generated here is used by LM1875 after LC filtering, and 7809 and 7909 generate plus and minus 9V for use by the pre-amplifier.
Using positive and negative voltages can remove the output coupling capacitor and reduce the impact on sound quality. The sound is still okay, after all, it is loud.
Theoretically, 5V-24V power supply is acceptable, and 12V is recommended. Just use a 20W QC charger to power it. The relay closes with a delay of 1S after powering on, and closes immediately when powering off. No POP sound is produced.
Disadvantages: The no-load current is not small, the DCDC efficiency is not high, and the heat is large. The temperature of the empty shell is about 40 degrees Celsius.
The inductor uses three wires of 0.6 enameled wire wound in parallel. One wire is about 50CM long. Be careful not to mistake the ends with the same name.
When debugging and installing, do not solder the power amplifier block first, and then proceed to the next step after the power supply is normal.
LM1876, after shaping the pins, insert it into the board, use thermally conductive silicone sheet, nylon screws and the shell to connect, and then solder the board on.
I made a new translucent front panel, but haven't soldered it yet. . . . . . . . .
Will update again when I have time. . . . . .
------------------Above 2021.10.24------------------------------ --------------------------------
I took the time to weld the front panel, and the LED can be a side-emitting 0805. Ordinary LEDs can also be soldered vertically.
Found a bug, the switch on and off positions are reversed.
R13 can be soldered with magnetic beads or directly short-circuited.
------------------Above 2021.10.27------------------------------ --------------------------------
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