Sorry to resurrect such an old thread, but I cannot contain my enthusiasm for the Parasound HCA-3500.
I owned one in the past and sold it, but decided to buy another used one a few weeks back.
Out of the box it was sort of harsh, forward, etched, and grainy. I thought BIG MISTAKE!
Five EASY and CHEAP things that I have done have dramatically improved my HCA-3500:
1. Using a Parasound P/LD-2000 preamp. [Theres a synergy there, after the mods are done].
2. Installed dedicated outlets with 20 amp breakers, one for each channel, on the amp. My other equipment goes into seperate outlets from these.
3. Changed out the R-44 resistors, [one on each side of the amp], from the stock Vishay 47K to Holco 47K. I got the Holco's at Michael Percy Audio.
4. The AC polarity on my HCA-3500 was reversed, just like the first one I owned, so I changed the wires around in my dedicated outlets.
5. Floated the earth grounds on both channels of the amps.
[The preamp is still connected to an earth ground]
Floating the earth grounds on both channels of the amp was the final thing I tried, and turned out to be the icing on the cake! After I floated the grounds, the sound became quite a bit cleaner, with much less grain and hash, a wider soundstage, and a more relaxed and somewhat more laidback sound, which is a plus with this amp.
Now the harshness, etch, and grain is almost completely gone, and I like the 3500 better than the JC-1's that I did own. The modded HCA-3500 is more lively, clear, dynamic, and has better treble dynamics, and depth than the JC-1's.
The JC-1's sound slightly muddy and vague in the mids and highs, and less dynamic in the highs, compared to my HCA-3500 believe it or not.
My HCA-3500 now has crystalline clarity, transparency, tons of detail, depth, a wide soundstage, and punchy dynamics
I am now going to experiment with aftermarket power cords.
Wow, what an improvement!