Musical Concepts amplifier modifications upgrades

Every one seems to be sastified with his work.

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.

I have a Musical Concepts modified Adcom 555 John did for me back in 1989. After reading the review in Absolute Sound ( Volume 13,Issue 55,1998)by Frank Kaplan I pulled the trigger and sent it in for mods. Unlike the one in the review I had mine turned into Dual Mono with Dupont Teflon caps and the Platium mods plus Edison Price copper binding posts. It came back sounding like a warm tube amp,gone was the edgy highs and the bass was tighter and more controlled. This amp has driven Vandersteen Signature 3's,Infinity RS3B's and Odyssey Lorelei's with no problem. I still have it and pull it out every once in a while and fire it up. I used it with the Adcom 750 pre amp that Musical Concepts modified to platinum level and it sounds very open,extended an imaging is dead on. 
I doubt you would be disappointed in the money spent vs. results.
Yes I moved on to a pair of Plinius 100's mark 3 in mono mode but the Adcom has a sweet spot in my heart even today.