GFA 545ii is an audio amplifier made by ADCOM uses the SANKEN 2SC3856/2SA1492 transistor which is capable of producing audio above 200Watts. The circuit using symmetrical sypply 56 VDC.
Many reviewer said that the amps is able to make 100 Watts audio power at 8 Ohm load.
SCHEMATIC DIAGRAM
This is an edited schematic diagram came from the original one:
From the above schematic, block diagram of the circuit is as follow:
Preamp. Its using 2SC2362 transistor.
Feedbcak limiter. Its using the OPAMP ADCOM3A. OPAMP located at input of the circuit.
Voltage Amplifier Stage. Its using 2SA1016K ( Q614) as Voltage Amplifier and 2SC2362K ( Q616 ) as Current Mirror.
NOTE
R632 must be connect with pin Base of Q606 and anode of D608. I think the drafter forget to make the joint wiring on this line wire.
The trimpot Q614 must be connect with pin Collector of Q614. Also its must be connet with collector of Q618. I think its something wrong with the wiring.
2SC3856 and 2SA1492 is a pairing Final Power Transistor which is able to reach audio power up to 130 Watts ( DATASHEETS ).
Therefore, the amplifier able to make the audio until 390 WDC ( 3 x 130W ) or 275 WRMS.
This means that at a load of 4 Ohm this power amplifier is still able to make better audio without overheating the power transistor.
