Class A and B headphone power amplifier implemented by OPA2188+2SC4672

This amp is modified from the failed OPA2197.

Code name: MZY7-R1KA

Production process video: [Hu-Fi] How to make a 250mW portable headphone amp with 50 yuan? -Bilibili

Changes:

• Changed from 47 headphone amp structure to large loop feedback Class A and B amplifier
• Give up TPS65131 (I really have no connection with this chip, the ripple cannot be suppressed) and change to SGM6601+TPS63700
• Replace the hard-to-find genuine OPA2197 with the easier-to-buy genuine OPA2188
• Add a headphone protection circuit, the action threshold is when the DC component exceeds 0.5V
• Enhanced EMI control of input and output

The overall structure is a Class A and B power amplifier composed of an op amp with a non-inverting amplifier connection and a large loop feedback. The picture shows the setting of the static operating point determined by Multisim simulation. At the same time, you can see that about 250mW of power can be obtained on 16-ohm headphones (1Vrms input, gain = 2), which must be enough to drive Shuiyueyu SSR.

After BOM calculation, you can get a Class A and B headphone amp with good sound quality for about 50 yuan. The panel is made of aluminum substrate. The Gerber file has been attached and you can proof it yourself at the aluminum substrate proofing factory. It can also be used as a single-layer PCB proofing, but the shielding performance will be lost.

The circuit has basically been adjusted and finalized. When welding, weld the positive and negative power supply parts first, and only after confirming that the voltage is about 6.5V can weld the subsequent amplification circuit. As expected, it can be used as soon as it is powered on.