Breadboard-only schematic for an ESP32-based LC electromagnetic response visualizer using a handmade coil oscillator, LM339 comparator, GPIO27 frequency input, SSD1306 I2C OLED, and calibration button. No PCB layout is included.
Compact 5 V-12 V mono audio amplifier with stereo 3.5 mm summed input, 10 kOhm log volume control, LM386 power stage, speaker output, power LED, and 2-layer 50 mm x 50 mm layout target.
Stereo 3‑Band Active Audio Equalizer and Mono Preamplifier using TL072 and LM386 with Right‑Angle PCB‑Edge CUI SJ1‑3535NG TRS Jacks for Jack Sensing and Routing
