WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

Page: 115 / 196

115
20 W Stereo Integrated Audio Amplifier
– Install R30 – 8.2 k
Ω
, 0.5 W – on the left channel speaker PWB in the position “ Rfb ”.
Solder in place.
In the next few steps, the speaker load resistors will be installed. As shown in the schematic
diagram of Figure 1.1, when the speaker switch is in the Off position, the secondary of each
output transformer is switched by a relay to a load resistor. The specified value for the resistor is 8
Ω
. This value can be difficult to find in stock components and so in this implementation, two 4
Ω
10 W resistors are connected in series to yield the correct value.
– Install R14 and R15 on the right channel speaker PWB. Place a 4
Ω
10 W resistor in the R
load A position and one in the R load B position. Mount so the devices are about 1/2-inch
above the PWB. Solder both devices in place.
– Install R16 and R17 – 27
Ω
2 W – on the right channel speaker PWB in the R head A and
R head B positions. Solder.
– Install R31 and R32 on the left channel speaker PWB. Place a 4
Ω
10 W resistor in the R
load A position and one in the R load B position. Mount so the devices are about 1/2-inch
above the PWB. Solder both devices in place.
– Install R33 and R34 – 27
Ω
2 W – on the left channel speaker PWB. Solder.
– Install C6 – 200 pF – on the right channel speaker PWB in the position “ Cfb ”. Solder in
place.
– Install C12 – 200 pF – on the left channel speaker PWB in the position “ Cfb ”. Solder in
place.
– Mount relay RYL1 on the right channel speaker PWB using the #4 hardware provided.
Orientation of the relay with respect to the board is not critical; however, it is suggested
that the pinout legend face the outside edge of the board to facilitate connections later. Do
not over-tighten the screws on the mounting pad or it may crack.
– Mount relay RYL2 on the left channel speaker PWB using the #4 hardware provided.
Orientation of the relay with respect to the board is not critical; however, it is suggested
that the pinout legend face the outside edge of the board to facilitate connections later. Do
not over-tighten the screws on the mounting pad or it may crack.