Page 33 of 36
R12 provides DC bias current for the positive input.
R7 and R8 set the power amp’s midband gain.
C4, C9, and R16 civilize the behavior of the protection circuits when the amp is
heavily loaded.
R9 unmutes the power amplifier when adequate voltage is present.
C7 and C8 provide power supply bypassing that aids the amplifier’s stability.
R11 and C3 form the Zobel network that helps stabilize the output stage.
The output of the amplifier goes off the board to the clamp mounted C7 via the
C7LPOS pin. The output of that capacitor returns to the board via C7LNEG.
That signal passes through the parallel L1-R10 combination that helps assure the
amp’s stability in the presence of capacitive loading.
K3 helps assure the absence of turn-on/turn-off pops and clicks. Assume that the
amp has been off for a while. Now, when the amp is turned on, K3 remains de-
energized until DC voltage is good, AC input is present, and the time delay
expires. During all that time:
o
The speaker outputs are disconnected.
o
C7 charges to its proper value through R31.
o
The amplifier input is muted
Once RLYDRV goes low (active), the relay coil is driven, and:
o
LED D9 lights up.
o
K3 connects LEFTOUT to the amplifier output
o
The SOUND node rises, removing the muting action on the input.
o
The amplifier is ready to reproduce the selected source.
