Hi,
I service McIntosh in a huge Mac town; Nashville, and have had several of the units you mention either owned by myself or serviced on my bench.
The MA6100 (and its MAC1900 receiver sibling) is one of the better platforms to work with as it is 100% discreet transistor circuitry,all the major boards are plug-in cards (easy to tweak and service) and it runs cool as a cucumber, plus the sonics are surprisingly neutral and musical for an early transistor design.
The later units; MA6200/MAC4100 used early IC OPAMPS and I feel these add a glare to the sound that was missing from the earlier units.
Stay away from the C32 as it used the first generation of FFC (flat flexible cable) ribbons and these will be delaminating and falling apart inside (once you remove one, you may not be able to reinsert it as it's now split open!).
Good luck replacing them; no longer available from Mc and replacement FFC's are not easily acquired.
I service McIntosh in a huge Mac town; Nashville, and have had several of the units you mention either owned by myself or serviced on my bench.
The MA6100 (and its MAC1900 receiver sibling) is one of the better platforms to work with as it is 100% discreet transistor circuitry,all the major boards are plug-in cards (easy to tweak and service) and it runs cool as a cucumber, plus the sonics are surprisingly neutral and musical for an early transistor design.
The later units; MA6200/MAC4100 used early IC OPAMPS and I feel these add a glare to the sound that was missing from the earlier units.
Stay away from the C32 as it used the first generation of FFC (flat flexible cable) ribbons and these will be delaminating and falling apart inside (once you remove one, you may not be able to reinsert it as it's now split open!).
Good luck replacing them; no longer available from Mc and replacement FFC's are not easily acquired.