KUSTOM PC703 POWER AMP

INFO

KUSTOM SOUND OF OSWERTRY launched custom PC703 Power Amp at 70s.

The Amp was able to make 70 Watts audio output at 4 Ohm load but need 40VDC symmetrically.

In this amp there is a tone control for guitar amplification and uses 2 x 10 inch speakers for monitoring guitar audio results.

However, in this article I will only show the schematic of the power amp.

YOU CAN DOWNLOAD THE SCHEMATIC DIAGRAM BY CLICK HERE

SCHEMATIC DIAGRAM

This is an edited and cropped schematic diagram of KUSTOM PC703.

If you look into the schematic diagram, it can be split in some block:

Firstly, The PreAmplifier that using simple differential amplifier system with both 2N4249 ( Q701 & Q702 ).

Next, Q703 as Voltage Amplifer Stage.

Third, Double Driver Transistor. Meanwhile there is 2 piece of transistor act as driver for the final power transistor.

They are Q704 & Q708 pairing with Q705 & Q709 for driving out the Final Power Transistor.

Finally, The Final Power Transistor Q1 until Q4 using part number 36892.

36892 equivalent with NTE130 transistor. It mean the transistor has the output until 115 Watts ( SOURCE ).

NOTE

The transistor able to make until 230 Watts of DC Output or 160 Wrms . But my calculation its can be reaching up to 144 Watts at 4 Ohm load if the Amp using 40VDC simetrically.