5khz noise from smps

nightanole · 1st July 2010, 01:09 PM

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?

AP2 · 2nd July 2010, 11:28 AM

Quote:

Originally Posted by nightanole

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

nightanole · 2nd July 2010, 12:10 PM

Meanwell Power Supply Products

Pafi · 12:20 PM

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.

AP2 · 2nd July 2010, 12:36 PM

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.

1st July 2010, 01:09 PM	#1
nightanole diyAudio Member Join Date: Feb 2009	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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2nd July 2010, 12:10 PM	#3
nightanole diyAudio Member Join Date: Feb 2009	Meanwell Power Supply Products

2nd July 2010, 12:36 PM	#5
AP2 diyAudio Member Join Date: Dec 2009 Location: Italy	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.