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assembly

steps

  • solder smd resistors (R1 - R7), check the solder joints with a magnifying glass for solid connection and the absence of shorts to near pads, once you solderer the small signal transistors you won't be able to access the smd resistors and troubleshooting will be a major pain
  • solder pins (in, out, v+, v-)
  • solder socket pins (bias testpoints)
  • solder trimpot (P1)
  • solder jfet (Q1)
  • solder small signal transistors (Q2 - Q7)
  • solder output transistors (Q8a + Q9a, Q8b + Q9b optional but recommended)
  • solder output resistors (R8a + R9a, R8b + R9b optional but recommended)
  • turn trimpots right turn to maximum ( = maximum resistance = minimum/no bias current)
  • install the buffers on the amp

PCB legend

please note:
"european parts" BC550 / BC560 / BF245C have reversed pinout compared to "US parts" 2n5088 / 2n2087 / 2n5486 !

click on pic for full scale image

part orientation

"US version" for 2n5088/2n5087/2n5486 parts"EU version" for BC550/BC560/BF245c parts

click on pics for full scale images

alternate pins

The dip pin headers mentioned in the parts list may be difficult or expensive to source. Alternatively one can deconstruct a dip-8 socket or a dip-pin-strip to get the pins needed for mounting the dDB board.
  • deconstruct a dip-8 socket or a dip-pin-strip to get the needed pins: heat the pin with the soldering iron and lift the pin out/up with a small plier
  • install the pins to a dip-8 socket
  • solder short wires (e.g. cut excessive leads from a resistor) into the pins
  • install the pcb on top of the pcb, fix it with a rubber band
  • solder the wires/pins to the pcb
  • cut excessive wire

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