Replacement PCB for Trace Elliot Bipolar Bear or 300W MOSFET.



Important note: I’ve discontinued this version of the drop in board, because the second revision of the drop in board is currently under development. I’m actually building the board as part of a stereo 400W power amp
unit, but I’m designing it in such a way as to allow the part to work as an an upgraded drop in Trace power amp board by using an adapter board that provides the connectors and mounting points for the Trace
biploar power stage.

I’m afraid I don’t have a timescale. I was hoping these would be completed by the end of 2020, but global events overtook me! You can follow progress by joining the Keld Ampworks Amplifiers facebook group and following the facebook pageĀ


300W Class D Power amp board. Drop in replacement to replace the obsolete ‘Bipolar Bear’ or the 300W MOSFET board in SM, SMX, SMC, 7-Band and 12-Band Bass Amplifiers.

The ‘Bipolar Bear’ design is known for being unreliable and almost unfixable. Trace Elliot used to offer a drop in replacement 300W MOSFET board, but ceased to do so after one of the many changes of ownership.

The board offers a number of features to make integration easy:

  • Reuses the bipolar bear heatsinks from the donor amp
  • Aligned to use the existing Trace Elliot fan.
  • Pin compatible input connector
  • Pin compatible AC input.
  • Pin compatible fan supply
  • Pin compatible speaker output
  • Because of the high efficiency of the replacement board, the Trace Elliot power supply is overrated and can be replaced with a lighter unit if required.

Because of the flexibility of the design, the board can also be ordered as a 150W module for 150 models.

Technology: Class D
Output Power: 150W or 300W into 4R
Input voltage
Weight: Super light!
Power consumption:

Additional information


300W, 150W

Construction Level

Bare PCB, SMT assembly, Full Assembly (no heatsink), Full Assembly (heatsink)


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