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



Wooo! Version 3 of the Trace Elliot drop in board will be shipping in July 2023.

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 MOSFET units later became a challenge to fix because of the availability of the lateral MOSFETs used by Trace


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

  • Use stock transformer or new SMPS (contact me for recommendations)
  • TEN YEAR WARRANTY when installed by Keld Ampworks or an approved technician. One year warranty for DIY or non-approved installation.
  • All discrete design.
  • Aligned to use the existing Trace Elliot fan (unlike Trace Elliot’s own boards!).
  • Pin compatible input connector.
  • Pin compatible AC input (see below).
  • Pin compatible fan supply.
  • Pin compatible speaker output (see below).
  • Delivers about 340W with the stock transformer (The 300W unit Trace unit was actually 280W).
  • Capable of higher power if transformer is replaced with SMPS (contact me for recommendations).

The MOSFET units use spade connectors for the power and speaker connections whereas the Bipolar units use Phoenix connectors. Contact me if you’re not sure and you can send me a picture of the innards of your amp. In fact send one anyway Trace have done some funny product variations over the years, it’s worth getting it right!

Technology: Class D

Frequency Response: 30-17kHz
Output Power: 150W or 300W into 4R
Input supply (transformer):  45-0-45 (Vrms)

Additional information


300W, 150W


Spade terminals (MOSFET), Green Phoenix Terminals (Bipolar Bear)


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