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General Category => Analog discussion => Topic started by: FrED on March 07, 2008, 06:46:45 AM

Title: How can i filter noise to audio?
Post by: FrED on March 07, 2008, 06:46:45 AM
Hello friends

I am a new member to your community and i would like to say hello to all  :)

I have a question. I have make an amplifier 60W hifi. It is for car use. I test it with power supply 220v and i get noise to the speakers. I suppose is because of the alternate current.

Is there any way to filter this noise?

Thank you
Title: Re: How can i filter noise to audio?
Post by: kam on March 07, 2008, 16:31:58 PM
First of all, make a good stable psu. Then if you have still noise you can use a 50/60 notch filter.

But first use a stable good psu otherwise you have problem. I beleive you have not stable power.
Title: Re: How can i filter noise to audio?
Post by: FrED on March 07, 2008, 18:42:46 PM
What do you mean stable? Because in terms of voltage, it is stable. Exactly 12.5Volts.
Title: Re: How can i filter noise to audio?
Post by: kam on March 09, 2008, 22:35:12 PM
I mean the power wave must be as straight as possible. You need actually a  very good PSU. Check some schematics in our circuits archive.
Title: Re: How can i filter noise to audio?
Post by: ScubaCap on March 13, 2008, 00:21:42 AM
Is 99% the psu not very well rectified. Try adding some big capacitors in paralel to your power supply. This may solve your problem.

Oh, and ensure that you have the power rectified. I mean, you must have some kind of diodes after the transformer.
Title: Re: How can i filter noise to audio?
Post by: FelIX on March 13, 2008, 23:12:41 PM
... or the capacitor in the input of the first transistor. Also very common problem.
Title: Re: How can i filter noise to audio?
Post by: FrED on March 22, 2008, 02:26:29 AM
Yes, must be the PSU. How idiot of me  >:(
Title: Re: How can i filter noise to audio?
Post by: Johnny2Bad on October 16, 2010, 17:01:35 PM
What do you mean stable? Because in terms of voltage, it is stable. Exactly 12.5Volts.

Then substitute a 12V battery for the PSU; a lead-acid car battery is fine.

If the noise remains, it's the circuit or a (lack of) shielding. If it disappears, it's the PSU.
Title: Re: How can i filter noise to audio?
Post by: raliana on January 02, 2012, 06:29:20 AM
When you design any amplifier and if at all it makes noise, then first of all you have to check whether there is stable PSU is there or not and if PSU is stable then you have to go for filter. Instead I have seen many people who doesn’t check for PSU and directly go for filters which is not advisable.Please have a look at your PSU first and then share the result here,if needed we can assist you in further diagnosis.