It adopts the line of British famous music fax A1 and the line of volume control, which has the advantages of simple assembly, good impedance matching and smooth volume adjustment. In the sound performance, you can broaden the sound field, increase the dynamics, and improve the resolution.The circuit is divided into two levels, the first stage op amp is responsible for buffering, and the second stage is responsible for amplification and feedback volume control (each op amp is responsible for one channel). Its characteristic is that the input impedance does not change when the volume is adjusted.You can also adjust the sound trend by changing different dual op amps according to your preferences. Most of the dual op amps can be used directly.The new version strengthens the PCB board, Taiwan's six-ring resistors, the new JRC5532DD, ELNA, Nissei, P-HILIPS capacitors, the power part uses the ON 7815/7915, SEP 306 rectifier bridge.Supply power: Dula AC12-25V, 7815/7915 voltage regulator on the board.size: 10.0 times 5.3CMProcessing technology: KB-level board high-precision CNC machiningSheet thickness and specifications: 1.6mm KB Class A FR4 sheetColour:Photo ColorMaterial:ABSPackage Contents:1 x Tone Audio BoardOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.