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Old 1st July 2010, 01:09 PM   #1
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Default 5khz noise from smps

I just built up an amp with 2 1500uf caps in parallel (41hz amp4) for the reserve caps. Im powering it with an external 24vdc 250watt smps with an 80mv ripple meant for plc's. I have a 5-8khz noise coming from the speakers that i can hear from a foot away, regardless of source.

Is there something i can do to remove the noise? Maybe a clc or crc filter?
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Old 2nd July 2010, 11:28 AM   #2
AP2 is offline AP2  Italy
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Quote:
Originally Posted by nightanole View Post
I just built up an amp with 2 1500uf caps in parallel (41hz amp4) for the reserve caps. Im powering it with an external 24vdc 250watt smps with an 80mv ripple meant for plc's. I have a 5-8khz noise coming from the speakers that i can hear from a foot away, regardless of source.

Is there something i can do to remove the noise? Maybe a clc or crc filter?
Hi,What type of SMPS you connected?
(To understand the noise at 5-8KHz)

Regards
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Old 2nd July 2010, 12:10 PM   #3
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Meanwell Power Supply Products
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Old 2nd July 2010, 12:15 PM   #4
Pafi is offline Pafi  Hungary
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Quote:
(To understand the noise at 5-8KHz)
Maybe it's the difference frequency between the carrier and some of the harmonics of the SMPS.

But nightanole could try to load it with a constant 10 W to check if it's a burst mode operation.

Quote:
Is there something i can do to remove the noise?
In most cases the grounding/shielding system is the culprit, not the SMPS alone. Try to alter things, and watch the result! As an experiment try to remove every unneccessary things (input selector, volume pot, even the input cable, short inputs instead)! Try to move SMPS away or closer! Etc...

In my experience the extra supply rail filtering never helped (at least in a single amp modul system), but you can try it also.

Last edited by Pafi; 2nd July 2010 at 12:20 PM.
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Old 2nd July 2010, 12:36 PM   #5
AP2 is offline AP2  Italy
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Hi,
very likely is a beat between carrier (amp) and SMPS.
can only be eliminated by varying slightly the frequency of the SMPS.
there is another way.
unfortunately I do not know this SMPS.
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