3.5mm input interface uses a 4-pole jack, with output connection for headset with microphone, compatible with mobile phones for standard voice calls. Additional terminal with莲花 (lotus) interface available. Control range: 7-band equalization circuit with ±12dB adjustment range at frequencies of 60Hz, 150Hz, 400Hz, 1kHz, 3kHz, 6.5kHz, and 15kHz, utilizing TI or ST TL074 operational amplifiers. Basic parameters: 7-band sound equalizer with pre-amplification gain; classic 4580 op amp provides 5x amplification (14dB); input impedance 20k ohms, output impedance 600 ohms. Compatible with headphones: sound equalizer ear amplifier section uses NE5532 and 47-type headphone driver circuit, capable of driving various headphone types with adjustable high and low frequencies. Constructed from aluminum alloy for high strength, corrosion resistance, and stable performance. Operates on DC 5V–12V power supply with dual-channel audio output.