For using 5.1 V USB voltage. Speeker may be 4, 8 or 16 Ohms. Excelent to increse Small TV or computer sound. Not necessary volume control. Volume may be controled by device you are conected. For estéreo you need 2 amp. Transistors may be BC series or equivalents. NPN BC338, 548, 639. PNP BC328, 558, 640. Not necessary heat seek. For diodes do not use 1N4148. Use 1N 4001, 2.4 or 7 because Vm.
