Strange problem with LM3886 (chipamp.com) - diyAudio
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Old 23rd February 2012, 06:30 PM   #1
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Default Strange problem with LM3886 (chipamp.com)

Ive ordered a dual mono kit from chipamp.com. Everything is working except that when I meause the OUT (to speaker) and OUT GROUND (to speaker) It shows that OUT is - and OUT GROUND is +. Ive also meausured between OUT and CHASSIS GROUND and I get the same that OUT is - and CHASSIS GROUND is +.

The funny this is that it plays good whether I connect the speaker to OUT or OUT GROUND.

Here is a link to the assembly guide and scheme http://chipamp.com/docs/lm3886-manual.pdf

Hope anyone can assist me in this!

Thanks!

BR
GM
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Old 23rd February 2012, 06:59 PM   #2
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DC Offset is:
left mono I get -73,5mV
right mono I get -59,8mV

Last edited by McDaisy; 23rd February 2012 at 07:23 PM.
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Old 24th February 2012, 12:46 AM   #3
6L6 is offline 6L6  United States
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Can you post some clear, well-lit pictures of your wiring? That would be an immense help.
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Old 24th February 2012, 01:40 AM   #4
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Quote:
Originally Posted by McDaisy View Post
DC Offset is:
left mono I get -73,5mV
right mono I get -59,8mV
Its because your dc offsets are negative.
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Old 24th February 2012, 02:00 AM   #5
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Quote:
Originally Posted by McDaisy View Post
Ive ordered a dual mono kit from chipamp.com. Everything is working except that when I meause the OUT (to speaker) and OUT GROUND (to speaker) It shows that OUT is - and OUT GROUND is +. Ive also meausured between OUT and CHASSIS GROUND and I get the same that OUT is - and CHASSIS GROUND is +.

The funny this is that it plays good whether I connect the speaker to OUT or OUT GROUND.

Here is a link to the assembly guide and scheme http://chipamp.com/docs/lm3886-manual.pdf

Hope anyone can assist me in this!

Thanks!

BR
GM
if output plus is the minus and output minus is the plus...just invert them!. I guess you made a mistake in the wiring.
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Old 24th February 2012, 06:01 AM   #6
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Quote:
Originally Posted by lanchile View Post
if output plus is the minus and output minus is the plus...just invert them!. I guess you made a mistake in the wiring.
Of course I alreaddy checked that and they are not mixed!

To be more clear.


The OUT GROUND is 0V and the OUT is -59mV so the out is actually a phase its just that its below zero. Why is this?
I called a friend with the same kit yesterday and he had the same issue. He wasnr aware of it and has been listening for a year very satisfied...


Strange
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Old 24th February 2012, 07:44 AM   #7
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Quote:
Originally Posted by 6L6 View Post
Can you post some clear, well-lit pictures of your wiring? That would be an immense help.

I talked with my friend who has the same kit. He has the exact same issue. He didnt know about it and he had been listening for almost a year very satisfied. Maybe this is correct..?

Anyways, since I have it in both channels and my friend has it in his both channels it cant be a soldering issue. Ive been soldeirng for 15 years so Im quite sure theres nothing wrong there. Im using a good weller station with appropriate temp and a suitable solder tip.
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Old 24th February 2012, 07:45 AM   #8
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Originally Posted by nigelwright7557 View Post
Its because your dc offsets are negative.

I know... The question is. Why are my dc offset negative?
Both my PSU's are giving the correct voltage out... and everything is properly connected.
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Old 24th February 2012, 05:08 PM   #9
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Hi

Im trying the math....are you measuring the offsets with the i/ps disconnected and do they vary with i/p pot setting (assuming your using some).
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Old 24th February 2012, 06:04 PM   #10
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I don't see how the DC offset being positive or negative would be an issue. I usually like to see it at less than 50mV. I assume you have the optional Ci installed. Lowering the value of R2 may help.

- Richard
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