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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
 
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
297 posts
 
Does changing the AC Polarity of the Sony SCD-1 make any sonic differences and/or improvements to its sound?
rcrump
427 posts
 
Think about it.......All the components are hooked together with interconnects that hook all the ground potentials together.......Just having one piece with the wrong AC polarity will destroy proper imaging of the entire system.....
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drubin
3,240 posts
 
What's the best way to check AC polarity? And what's the best way to change it if needed?
daltonlanny OP
297 posts
 
Get a voltimeter first.Unhook all interconnects and speaker cables from the amp.Get a 'cheater plug'[a plug which you plug your 3-prong plug into,but only has 2 plugs on the end of it that plugs into the electrical outlet].Ground down the end of the biggest prong on the 'cheater plug' so that you can reverse it around 180 degrees and plug it in the opposite way in electrical outlet.
Plug the amp power cord, one channel at a time, into the cheater plug.Plug the cheater plug into the electrical outlet the normal way it would go in if it had 3 prongs.Turn the unit on.Place the black lead of the voltimeter to an earth ground or very good ground, then touch the red lead from the voltimeter to a chassis screw on te amp or to the outside of the RCA input on the back of the amp.Note the voltimeter reading and write it down.Now turn the unit off, unplug the cheater plug from the electrical outlet and plug it in the opposite way,180 degrees.Do the same things I named above:Turn the unit back on, use the leads from the voltimeter in the same way, and note the reading. THE LOWEST READING IS THE CORRECT POLARITY.If the polarity is reversed, the lowest reading will be obtained with the cheater plug reversed 180 degrees.
If it is reversed,MAKE SURE THE UNIT IS OFF AND UNPLUGGED FROM THE OUTLET, take the top cover off.You will see the input screws that holds the wires down from the main-input sockets on the back of the amp.You will see that there are two red wires from the input socket on the amp.One goes to the fuse, then from the fuse is a white wire.The white wire goes to a screw labeled 'IN'.The other red wire goes to a screw labeled 'OUT'.Remove the screws and switch the red and the white wires around then put the screws back in.This is one channel.Now do the other one the same way.After, you do this replace the cover, plug the unit back in to the cheater plug and do the same test again just to be sure its right.Do not remove or replace the Green Ground wire inside the amp!PLEASE BE VERY, VERY CAREFUL WHEN DOING ALL THIS AS DANGEROUS OR DEADLY ELECTRICAL SHOCK CAN OCCUR!!Hope this helps.
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