The M³ stereo headphone amplifier

Notes about M³ v1.01 circuit board

Before you use the board, please read the notes below.

Enhancements from v1.00

  • All electrolytic capacitor hole sizes have been enlarged to accommodate certain "boutique grade" capacitors with extra thick leads.
  • The footprint for all the C5 and C6 film capacitors have been enlarged.
  • The D1 diode symbol has been changed to be more illustrative.
  • The power planes for V+ and V- have been enlarged slightly.
  • Some minor cosmetic board silkscreen changes.

Errata: IG pad error

There is a minor new issue with the v1.01 circuit board.

As with v1.00, there are two input blocks, each consisting of 5 pads labeled IG-IL-IG-IR-IG. Input block 1 is at the rear of the board, near the TLE2426 rail splitter. Input block 2 is near the volume control potentiometer, next to the small M³ logo.


Due to a layout flaw, the IG pads at Input block 2 are not connected to the ground plane as they should be. Input block 1 does not have this error. If you will be using any of the IG pads at Input block 2, then you must fix this error by soldering a wire jumper from the IG pad to a pad that's connected to the ground plane. The positive (square) pad for the C5L- capacitor is the closest candidate. This fix is best made on the bottom (solder) side of the board.

If you won't be connecting anything to Input block 2, then no fixes are necessary.

See the following illustration for an example of the fix, where all three IG pads are bridged and then connected to the ground plane at C5L-. You can use clipped resistor leads as the wire jumpers.

This error will be corrected in the layout for the next revision.