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Old 27th July 2015, 01:11 AM   #1
Alekk is offline Alekk  United States
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Default LM3886, Working but needs work.

Few days ago, got my fun little chip amp in the mail, along with a few extra goodies from the chipamp website. Decided to go with the Nichicon Gold Tune filter caps, and replace the Panasonic FCs on the amplifier boards with Elna SILMIC IIs of the same values. During the build, only things that irked me is the missing PS LED cap and LED. Also, those Elnas are much larger than the FCs, making everything on the board a bit cramped when trying to get it as close to the board as possible.

Had scrap parts from an Onkyo TX-DS595 that sat in the attic (why it was up there, I will never know), including a decent EI transformer (NPT-1411D) with some 19.5-20v secondaries that I could use for the build. They were pre-wired in series, of course, so I had to pop all of them apart to get everything where I needed it. Otherwise, the build went as planned, save for the hum that I currently have when it's powered on (I believe the core of the transformer needs to be properly earthed to eliminate a bit of residual hum).

Next few things to get done:

-Get a steel chassis.
-Organize the rat's nest. Please, don't hate me for it, moved from a bench testing case directly to this wood... thing, temporarily...
-Shielding/earthing the transformer mount without creating loops/shorted turns.
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Old 27th July 2015, 05:24 AM   #2
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wires are too long. Are you using same cable for power and signal? use shielded cables for signal connection.
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Old 27th July 2015, 05:34 AM   #3
Alekk is offline Alekk  United States
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Yeah, ran unshielded temporarily to verify that all the components were in working order. Keep in mind that I've only had it for a few days. As for the length of the wires, the only wires I have over 8" are running from the transformer to the power supply, as I plan to take out the entire thing and move it to a steel chassis, then trim the wires further down.
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Old 27th July 2015, 07:05 AM   #4
Philfr is online now Philfr  France
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Hi Alekk,
Make cables as short as possible, and twisted by pair for input and output, by triplet for PS..
I think hum disappear
Good luck, and enjoy this good amp.
Phil.
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Old 27th July 2015, 09:04 AM   #5
AndrewT is offline AndrewT  Scotland
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Every current flow has a current return. These two Flow and Return wires MUST be identified and close coupled. NO EXCEPTIONS
Do this for EVERY Flow wire.
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