Finally got some pics of my HCA-3500! Went through some SERIOUS mods. About $1,200 in parts and over 80 hours of soldering! It literally took 5 revisions, swapping out parts, values, etc to try and solve the ground hum and top end harshness. Keep in mind this is running my Wilson Watt Puppy 7s, which are infamous for being very analytical and and bright on the top end. This amp has never sounded so neutral and revealing. The mods added another layer of dimension to the imaging, heightened dampness and the control over the bass is incredible, super fast and tight. The high's are sweet and clean, no more hurting my ears!
The primary changes involved: altered the balanced input to be straight pass through (for some reason Parasound changed the balanced input path making it single sided, weird). Replaced multiple smaller in-line caps with single larger higher quality Holco, PolyStyrene RelCap and/or DynaCaps (depending on values). Swapped out the big crappy Bridge Rectifier with (4) FREDs. Then used the old Rectifier in the Power Supply to solve the ground hum/hiss by mating it with a resistor and cap (as seen in all Bryston amps). We had a really difficult time trying to fit everything, the higher quality caps are physically larger than the stock ones. We tried to keep it pretty, but there is only so much you can do!