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How do I get rid of static noise?

TerThesz

New Member
Hello
I've made an audio mixer (with only one input just so I can test if it works) and it does work but I'm hearing a static noise that I can't get rid of.

Here are some photos
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20221106_011655.jpg
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Any help will be highly appreciated
 

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audioguru

Well-Known Member
Most Helpful Member
Your transistor has no negative feedback then its voltage gain and distortion will be very high.
The mess of wires all over your breadboard are antennas that pickup all kinds of electrical interference.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Some of the noise is likely from the power supply - see the video below.
Adding an actual ground (earth) connection to the mixer 0V may help, or running the mixer from a battery rather than a power supply.

Or, between that and the laptop ground - assuming you are connecting to an input on the laptop?

PC / laptop audio inputs are frequently noisy if whatever is connected to them has its own wall power connection, due to circulating ground currents. You can often prove that by running different programs & the noise will change depending on CPU / GPU loading. An audio isolating transformer can help there, to break the DC connection.

Also, you are trying to get extremely high gain with non-optimal component values; try removing the cap across the 100 Ohm resistor, or add another 100 Ohm in series with that cap.

(And as the other answers say, keeping wire lengths down can help reduce stray noise pickup).

I did this as a demo for another member of this site, that was having noise problems with an audio project running on a wall wart type PSU:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Well that's not a mixer - dump that crappy design - use an opamp as a 'proper' mixer. there are hundreds of simple designs out there.

As for static noises, it doesn't show the essential power supply decoupling components, and it's incredibly badly built - don't use breadboards!.

It's very, very, simple to make an opamp mixer - I once made one in 20 minutes from scratch (in a tobacco tin), as I had a disco to do :)
 

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