JBL EON15-G2 Technical & Service Manual page 17

LF Amplifier Stage
All Voltage measured with reference to audio ground with no input signal
The low frequency amplifier uses discrete components configured in a push-pull drive
architecture operating in the class AB region and have a measurable gain of 18.52 dB.
The voltage rails for the power amplifier are ±40 Vdc as rectified by bridge BR1 located in the Power
Supply Module. The output and driver transistors are driven by the preceding stages, which make use
of the bootstrap supply voltage of ±80Vdc.
The low frequency processed signal from pin 8 of U3-C enters the differential amplifier consisting of
Q4 and Q5 subject shutdown from Q6.
Physically attached to the heatsink, Q13 dynamically controls the bias for the output transistors and is
statically adjusted at VR1.