The opa2604 is good, the sound quality is not bad. The OPA2604 is an 8-pin dual op amp, that is, two op amp modules are integrated in a chip, and the use of positive and negative dual power supplies can complete the amplification work of stereo dual channels. The op amp has mellow, round tone, neutral warm, and strong gallbladder taste. It is known as an op amp with vacuum tube tone.