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Old 8th June 2005, 06:24 AM   #1
wuffer is offline wuffer  Denmark
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Unhappy first atemp to make a gc gone wrong

i have just made the gc from http://sound.westhost.com/project19.htm but with the lm3886 instead and this psu http://sound.westhost.com/project04.htm but with 4700 caps instead.. im using a 2*24v 300va trafo
i have no pcb so i have just wired the components together..

the big problem is large noise/hum and a tiny bit of music...

i cant see what i have done wrong... can you experts give me a hint what i have done wrong???

sorry about my poor english
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Old 8th June 2005, 11:58 AM   #2
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Check your wiring,then recheck your wiring espeicially ground.

Check your power supply for correct voltage.

Make sure pin 5 is connected to + power supply
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Old 8th June 2005, 12:09 PM   #3
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also make sure you have something like a 10K resistor from the negative rail to the the mute pin.
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Old 8th June 2005, 12:17 PM   #4
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If you haven't downloaded the datasheet and the AN-1192 do it because there is everything you need.

http://www.national.com/an/AN/AN-1192.pdf
http://cache.national.com/ds/LM/LM3886.pdf
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Old 8th June 2005, 12:20 PM   #5
wuffer is offline wuffer  Denmark
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thanks all... i will check again and hope i can get it to work
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Old 8th June 2005, 01:12 PM   #6
wuffer is offline wuffer  Denmark
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i got it to play but some parts went up in smoke im not sure wich... but it was very low music...
new parts and then i will see if it works
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Old 8th June 2005, 01:38 PM   #7
Nuuk is offline Nuuk  United Kingdom
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Wuffer, if it helps to copy a 'tried and tested' design for the LM3886, here is the one that I built. I have not had time yet to write up the full description of the build on Decibel Dungeon.

The orange square is the signal star ground. And note that this was with a snubberized PSU. If you don't want to use that PSU, substitute the 100uF caps on the voltage pins for 1000uF and leave out the big caps at the bottom of the diagram.

Click the image to open in full size.
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Old 8th June 2005, 04:05 PM   #8
wuffer is offline wuffer  Denmark
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much closer now... i think the wire i have used is bad.. it influence the sound in a bad direction... not sure what to do...

damn the lm3886 is getting hot. hat hoped that a heatsink from a p4 could be used but no

but now there is music coming out of the speaker instead of noise.. now i just have to get the last noise away
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Old 8th June 2005, 04:21 PM   #9
macboy is offline macboy  Canada
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Quote:
Originally posted by wuffer
much closer now... i think the wire i have used is bad..
Unlikely.
Quote:
Originally posted by wuffer damn the lm3886 is getting hot. hat hoped that a heatsink from a p4 could be used but no
[/B]
If the 3886 is getting hot, then your amp is probably oscillating badly. I've used heatsinks much smaller than a P4 one, and at low to medium volumes, the chip gets only slightly warm.

Tear it down and start again from the ground up. Nuuk's diagram looks solid; try following that.
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Old 8th June 2005, 04:37 PM   #10
wuffer is offline wuffer  Denmark
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okay thanks.. i will do that later
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