This is a circuit schematic Audio Tone Control , this Tone Control very compatible with Amplifier using TDA 2003. Below the schematic of Tone Control :
If you can't see the component's you can click to view larger or you can tell me about it. Transistor using C828.Which Potentio from left Bass then Treebel and last right Volume. Voltage for this Tone Control need about 12VDC - 25VDC.