M400 plus is a new upgraded series based on M400. From appearance to circuit architecture, it uses AKM’s new DAC chip-AK4499, and focuses on the power supply. It is equipped with 8 Panasonic 330UF E-type tantalum capacitors, 4 OPA1612 is used as IV conversion, full firepower, each 4499 has 4-channel output, each channel has an IV conversion, non-castration design (some products only use 2 IVs for each 4499), and finally merged. To achieve a very high level of sound quality, the volume control adopts Texas Instruments PGA2311UA, 2 pieces, combined into a 4-channel synchronous adjustment, no dynamic compression, no partial sound, long life, secondary screen display volume, gain, DAC filter Wait, the balanced output uses the 4.4 output port, retaining the grounding function. Compared with M400, M400plus is upgraded as follows: 1. The shell technology is greatly improved, the glass is changed to 2.5D, and the texture is better. 2. On the premise of retaining the original high-definition asynchronous USB input, a new Bluetooth input is added, using the CSR8675 main control, supporting LDAC, APTX-HD, APTX-LL, APTX, AAC, SBC and other protocols. 3. Add AK4118 for digital processing 4. The battery capacity is increased to 5000mah, and the battery life exceeds 7 hours. 5. Bluetooth mode supports call function. 6. Newly added wireless charging function, Qi standard, supports 7.5W wireless fast charging without interference. 7. Improve the problem of USB input interface protruding too much and easy to loose. 8. Optimize the IV circuit, LPF circuit, coupling capacitor, reduce the current sound, make the sound low and clean, improve the high frequency, human voice, low frequency, better transparency, and solid low frequency. 1. Parameter listUSB chip-asynchronous SA9227 32bit/384KHZ & DSD256Bluetooth chip---CSR8675Bluetooth protocol---LDAC, APTX-HD, APTX- -LL, APTX, AAC, SBCDecoding chip---AK4499EQIV conversion op amp-0PA1612*4LPF op amp----0PA1612*2AMP------Customized op amp two +8 power tubesVolume control - -2 PGA2311UA+TI positive and negative power supply + TTC encoderOp amp working voltage-10V differential pressureInput interface---Type-C inputOutput interface---3.5 L0 output, 3.5 P0 output, 3.5 coaxial output, 4. 4 balanced outputOutput level value-single-ended MAX: 4. 25VRMS balanced MAX: 8.5VRMS no loadSignal-to-noise ratio ----- single-ended 125DB, balanced 130DB, 1KHZ 32 2THD+N distortion--. Single-ended 0.0007%, balanced 0.0006% 1KHZ 32?Output impedance---single-ended 29, balanced 12Power-----Single-ended 32 Q 380mw, balanced 1250mwBattery------3.7V 5000mah lithium batteryCharging-----5V 3A, MAX: 15W; wireless charging: MAX: 7.5W QI standardBattery life--USB mode: about 7.5h, Bluetooth mode: about 7hBody size---120mmX75mmX18mmWeight-210 grams