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Improve the Sound of your Parasound HCA3500

How many of you out there have checked the AC Polarity on your Parasound HCA-3500 power amplifier? There is a 70% chance its reversed!Mine was also.You can improve the bass, imaging and coherency by changing it around.
Another way to improve the sound is to change the main feedback resistors [r-44 on the circuit board].Remove the Vishay 47K resistors and replace them with Holco 47K resistors.You can obtain the Holcos at Michael Percy Audio.The main feedback resistors are located near the back of the unit and alittle over half-way up on the side circuit boards.There is one on the right circuit board, and one on the left.Again, numbered R-44.This eliminates the grain and edge in the highs and the unit sounds more open.Both these mods together make a big improvement in the sound! I got this idea form John Curl and Bob Crumps posts on audioasylum.com.Try them, they definitely work!
daltonlanny
rcrump
427 posts
 
R-44 is actually about half way back and the third component from the top of the board on each side as I recall, but it is marked...........Posted this a few years ago on AA and this will make for a much better amp.....Lots more to do, but the main feedback resistors and getting the AC polarity right are steps in the right direction......Lethal voltages in the amp so unplug it before doing anything.......
daltonlanny OP
301 posts
 
Why were so many of these amps built with the wrong AC Polarity?
rcrump
427 posts
 
Why were all the Sony SCD-1s built with the wrong AC polarity? Nobody checked it at Sony and nobody checked it at Parasound's contractor until Parasound instituted a procedure almost two years ago.....
daltonlanny OP
301 posts
 
Does changing the AC Polarity of the Sony SCD-1 make any sonic differences and/or improvements to its sound?
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