AMB Laboratories
The ε22 Amplifier Backplane Board

Notes about ε22 v1.00 circuit board

There are a few issues with the v1.00 circuit board. Before you use them, please read the notes below.

Silkscreen label error

There are two Molex headers labeled "J10". One of these is the speaker output connector, which is correctly labeled. The other one is the LED connector, and this one should be labeled "J15".

Rg size

The ε22 board will accommodate only the 22mm 5W cement-filled wirewound resistors listed in the β22 website parts list. The silicon-coated wirewound resistors listed will not fit.

CzL and CzR size

The ε22 board layout accommodates 0.300" (7.5mm) lead pitch for these capacitors. For capacitors of different lead pitch, you will need to bend the leads.

Molex KK .156 header holes

As delivered from the factory, the pad holes for all Molex KK .156 headers were too small (affecting J10, J11, J12, J13 and J14).

Prior to shipment, these holes have been enlarged at AMB Labs to allow the Molex header pins to fit through. However, the re-drilling removes the through-plating in these holes. Some of the pins must be connected to traces on both the top and bottom copper layers.

Follow the procedure described below to correct this problem.
Note: You need to perform the following procedure only on the following connector pins:
  • J10: all pins
  • J11: no correction needed
  • J12, J13, J14: "Out" pin
  1. Solder the Molex KK .156 headers to the board on the bottom side (as they are normally done).


  2. Use a butter knife or a thin-bladed screwdriver, gently pry the plastic base of the header upwards. Use even pressure to avoid breaking the plastic or bending the pins. Do not slide the base completely off the pins.


  3. Solder the pins to the top copper layer pads. Use just enough solder to form a small concave cone around the pins, but no more.


  4. Push the plastic base back down.


  5. You are now done.