Noise from my TPA3122D2 amp - diyAudio
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Old 3rd May 2013, 03:23 AM   #1
Lo_Tse is offline Lo_Tse  Canada
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Default Noise from my TPA3122D2 amp

I bought the kit from Sure Electroninc on EBay. I think this kit is the same as the one on sale at Parts-Express. Soldered everthing and the amp worked with no issue. The power supply that I use is an old lab top brick (+-19V). The sound was much better than I expected. Quite enjoyable.

However, as I listened more carefully, I heard some low level hissing noise . I confirmed that by putting my ears right in front of the speaker drivers (tweeter). It did not sound like some kind of background noise because the noise seemed to be modulated by the signal i.e. when the sound level is higher, the noise got higher. Also, the noise seemed to follow the music's rythym too!! I suspect the noise is associated with the power supply. Those lap-top switching PSU are known to be noisy. Does anyone has similar experience?

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Old 3rd May 2013, 04:15 AM   #2
DUG is online now DUG  Canada
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Hi Lo_Tse

Perhaps a mixing of the two switching frequencies.

Try an L - C - L - C filter to really clean up the supply lines?
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Old 3rd May 2013, 12:26 PM   #3
Lo_Tse is offline Lo_Tse  Canada
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Originally Posted by DUG View Post
Hi Lo_Tse

Perhaps a mixing of the two switching frequencies.

Try an L - C - L - C filter to really clean up the supply lines?
Hi, DUG

Thank you for the suggestion. I am thinking along similar line - may be I should rig up a linear psu with a CRCRC (I have no inductors in my bin) filter bank and try it out.

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Old 3rd May 2013, 12:36 PM   #4
DUG is online now DUG  Canada
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If that is the issue...I have some...when is the next Toronto meet?

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Old 3rd May 2013, 10:59 PM   #5
Lo_Tse is offline Lo_Tse  Canada
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If that is the issue...I have some...when is the next Toronto meet?

DUG,

Thank you in advance. I am not sure. Missed you last time. I guess it depends on how interested people are in getting together and whether someone is willing to host. Soon, I hope!

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Old 4th May 2013, 01:49 AM   #6
xrk971 is online now xrk971  United States
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Tpa fans! I wish I was in Toronto area to drop by your meets. I have had more noise on bricks that are not grounded (2 prong wall plug) vs grounded (3 prong).

Dug, I am still enjoying my tpa3116d2 very much thanks to you. I need to design a pcb and order boards and make more. They are so useful to have. Being so small it makes sense to put them inside speaker cabinets for powered monitors.
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Old 4th May 2013, 02:08 AM   #7
Lo_Tse is offline Lo_Tse  Canada
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Hey, xrk971

I was thinking about that too. The cable that connect my "brick" to the wall is three pronged. However, between the "brick" and the amp board, only two => + and -. So my interpretation is that there is no ground. I do not know whether it is good or bad. I guess the amp does not need a "ground" per say, as long as there is a signal return.

Apart from the noise, my 3122 amp sound pretty decent. A TPA3116D2 amp is definitely in my near future .

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Old 4th May 2013, 02:33 AM   #8
xrk971 is online now xrk971  United States
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The ground is internally connected to the ground or non positive 19 v line. Your power supply is not the problem, switching power supplies are actually pretty quiet at audio frequencies. The 3122d2 uses electrolytic caps on the output side, make sure those aren't damaged or in backwards, or maybe not rated for 38 volts? I think output voltage can swing double the input rail? If it is 35 volt rated cap, you may be getting some leakage. Try 50 volt caps.
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Old 4th May 2013, 12:55 PM   #9
Lo_Tse is offline Lo_Tse  Canada
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Originally Posted by xrk971 View Post
The ground is internally connected to the ground or non positive 19 v line. Your power supply is not the problem, switching power supplies are actually pretty quiet at audio frequencies. The 3122d2 uses electrolytic caps on the output side, make sure those aren't damaged or in backwards, or maybe not rated for 38 volts? I think output voltage can swing double the input rail? If it is 35 volt rated cap, you may be getting some leakage. Try 50 volt caps.
Thanks for the tip. I'll check again.

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Old 5th May 2013, 10:47 PM   #10
DUG is online now DUG  Canada
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Update on my TPA3116 that I had at the show.

Put it in a box with some other stuff and I have some "noises" similar to what you may have heard with your amp / SMPS combination.

I had a piece of one sided pcb and some very low ESR caps and chokes laying around (inductors from computer PS...output filters, the common mode choke from computer ps)

put some cuts in it and drilled some holes (most in the right place)

Threw in some 0.1uF 0805 caps as well

built a filter and installed it...no more SMPS noise.



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Last edited by DUG; 5th May 2013 at 10:49 PM.
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