Musical Concepts amplifier modifications upgrades

Rather than upgrading the existing design of the amplifier, Mr. Hillig specializes in a redesign of the amplifier. He chooses certain amplifiers as the "bones" on which he builds his own design.
He generally uses the transformer and portions of the power supply, pots and switches while most of the existing circuitry is replaced with his own circuit boards.
I have a couple pieces which he has redone; a Hafler DH-101 preamp and a DH-500 power amp which are significantly better sounding than the originals. I am also currently using a Musical Design D-140 which is his own brand.

I highly recommend his work.   

It appears that new driver boards are limited to the Hafler Power amps at this time, but I think they were once available for the Adcom power amps also.

He does do upgrades using his MC-3 circuit board on certain Adcom preamps as well as outboard power supplies, though.