Solved Audio Noise

[sl33pydog]

I've tested this cheap 5V amp from Drok with the same power supply and speaker set up but I changed the L, G, and R input signals for a headphone jack and no noise even at the highest volume input and output. I tried this on the game cube first through the amp and now through the dol chip (pins 1 and 4) see pic below. I also tried relocating the input ground to other ground pads. I'm getting bad noise especially on the normal gamecube menu screen. It's a buzzing sound. What do you guys think the issue is? Is it my cable length? Not having a ferrite ring in there?

 

[Noah]

Honestly? Could be a lot of things. What else is connected to the power line you're using to power the amp?

 

[Shank]

There are a lot of different types of "buzzing." Pics of your full setup and and a recording of the audio can help.

For troubleshooting, If you have another amp, try running your gamecube into that to see how it handles. You can also try powering the amp off of a separate voltage supply other than the gamecube. (just be sure to connect the grounds together)

If it's airborne interference from nearby electronics, try using shielded wire. You can find shielded wire in RCA plugs. Be sure to connect the shielding to ground. Also some regulators are noisy, and shielding them can greatly reduce interference. Post pics pls.

Check your voltage of the power supply powering the audio amp. You want to make sure it's outputting the desired output under load.

If your power supply is still noisy, try adding a large capacitor to the voltage line powering the audio amp to clean up the power supply.

 

[sl33pydog]

@Noah on the 5V rail I have the controller, fan and pam style amp. The picture below should show the regulator setup. I went back to another regulator board to see if that would help but no dice.

@Shank The buzzing sounds more like clipping on a guitar amplifier. It happens more on the main menu and then does something funky everytime the light on the megadrive turns on. Finally the last two times I turned it off I heard popping like when you disconnect an input out of a live amplifier. Not sure why.

I tried the sheilded wire but it didn't help much. What did was change from the 5V to the 3.3V. I'll add a cap to the line to see if that helps for the 5V.



Thanks guys for the help

 

[Aurelio]

I tried the sheilded wire but it didn't help much. What did was change from the 5V to the 3.3V. I'll add a cap to the line to see if that helps for the 5V.

This might mean that the amplifier is too powerful for the speakers you are using. What kind of speakers are they?

 

[sl33pydog]

2W 4ohm. the drok is 3W each at 5V

 

[Aurelio]

2W 4ohm. the drok is 3W each at 5V

Do you hear the noise if you lower the volume?

 

[Shank]

You need some output caps for your regulators. Without output caps, the signal is going to be very, very noisy. I don't think the SMD ones you have there are enough.

Edit: also, what voltage is this amp designed to run on, and what voltage are you running it at?

 

[sl33pydog]

Do you hear the noise if you lower the volume?

Yah but it was lessened by the shielded wire and going to the 3.3V regulator.

 

[sl33pydog]

You need some output caps for your regulators. Without output caps, the signal is going to be very, very noisy. I don't think the SMD ones you have there are enough.

Edit: also, what voltage is this amp designed to run on, and what voltage are you running it at?

The SMD ones are 100u at 17V. Thought that should have been enough like the diagrams out there. I tried the additional 100u cap on the amp and it didn't clean it. I think it's my input lines that aren't clean because with the GC running I switched the input cables to a stereo male connector and connected it to my phone without any buzzing issues.

The amp is designed for 3-5.5V. I tried it with 3.3V and 5V with similar issues.

 

[Aurelio]

The SMD ones are 100u at 17V. Thought that should have been enough like the diagrams out there. I tried the additional 100u cap on the amp and it didn't clean it. I think it's my input lines that aren't clean because with the GC running I switched the input cables to a stereo male connector and connected it to my phone without any buzzing issues.

The amp is designed for 3-5.5V. I tried it with 3.3V and 5V with similar issues.

Ok in this case the problem is the GC. Do you hear noises both directly from the dol and also from the output of the preamp?

 

[sl33pydog]

Ok in this case the problem is the GC. Do you hear noises both directly from the dol and also from the output of the preamp?

Both. And the weird part is that the noise is oscillating ~30times per 10seconds

 

[Aurelio]

What are you using to power your gc?

 

[sl33pydog]

I have a korad power supply to my gc regs on the pcb I made.

 

[cheese]

I have a korad power supply to my gc regs on the pcb I made.

Have you tried putting a resistor or capacitor between the amp and audio source? It's possible there is some DC power on the audio out lines, or that the amps may be pulling too much power from the dol.
For a cap, it doesn't really matter the capacitance, mainly that the negative is on the input and the positive goes to the output. This removes any DC that could be on the audio line.

 

[sl33pydog]

 

[cheese]

I meant the minus of the cap goes to the audio out on the dol, and the plus goes to the audio in on the amp. The capacitor will allow the alternating power through (the audo), but if there's a DC offset on the audio line, it will get rid of that.

 

[sl33pydog]

I meant the minus of the cap goes to the audio out on the dol, and the plus goes to the audio in on the amp. The capacitor will allow the alternating power through (the audo), but if there's a DC offset on the audio line, it will get rid of that.

same thing. Buzzing noise.

 

[cheese]

Try bridging the grounds on the power in and audio in?

 

[sl33pydog]

tried that and on a new gamecube....same thing.

This is another strange part. So it's louder when I turn the volume up (duh on my part) but when I put the volume to min I can't hear the gamecube but I can still hear the buzzing but only slightly. Is this the dc offset you were talking about?