2SC828 is an NPN, Silicon-based AF Amplifier Transistor that is mainly used in AF based audio equipment for amplification and switching. It has a Collector-Emitter Voltage of 45 Vdc with a Collector-Base voltage of 45 Vdc.
The 2SC1061 is a NPN Power Transistor in To-220 package. It has a DC current gain from 35 to 320 and transition frequency of 5MHz. It is commonly used in high power amplifier application along with its complementary PNP part 2SA671.
The BC546 is a high frequency NPN Transistor commonly used in low noise amplifier designs. It has a maximum gain value of 800 and a high collector to emitter voltage of 65V making it also suitable for high voltage audio amplifier applications.
The MPSA18 is a General Purpose NPN Transistor which can operate with low noise and high gain. The transistor has a gain value of 500 to 1500 and can operate at a voltage of 45V with 200mA load current.