Noise Reduction in Audio/Video Switching Circuit

[xTamx420]

Hello,

I'm working on an audio/video switching circuit for old video game systems that use RCA jacks for left and right audio.

I've noticed a great deal of humming/buzzing in the audio which I would like to eliminate if possible.

I put 0.1 uF capacitors connecting the positive and negative lines for the output jacks and that seemed to clear it up a fair bit. I've also got 0.1 uF and 10 uF filtering caps on the switching ICs.

Is there anything else I can do to eliminate the remaining hum? I tried 0.01 and 1 uF caps too but they didnt really work right. The 0.01 uF caps seemed to do almost nothing and the 1 uF caps seemed to remove the higher pitch sounds leaving mostly bass. I dont have any other capacitors on hand but I could order some more in the 0.1 to 0.5 uF range and try those out maybe?

Is there anything else I can do besides caps on the outputs?

 

[Arouse1973]

Hi can you show us a picture of your connections?
Thanks Adam

 

[xTamx420]

heres a couple of pictures. Pretty messy I know but its only a prototype at this stage. I'll be getting PCBs printed for the final version. I've added a few more caps and the noise is nearly gone too but still not completely gone.

 

[Arouse1973]

I think that might be your problem, all those wires with no screening.
Adam

 

[xTamx420]

So if I had a proper 2 layer PCB you think it might be better? I've got it fairly good on the breadboard now too.

The final version is going to be larger though. It will be this circuit repeated 8 times so there will be a fair number of traces on the board.

 

[Arouse1973]

It should help yes. But it the connection that are important. Can you post a drawing of your connections?

 

[xTamx420]

sorry what do you mean by connections? I am very much a beginner when it comes to electronics.

 

[Arouse1973]

You have connection in and out of your bread board. We need to identify which ones are video and which ones are audio.
Adam

 

[xTamx420]

would a schematic help?

 

[Arouse1973]

would a schematic help?

Yes it would.
Cheers
Adam