SNES sound distortion issue

Discussion of hardware and software development for Super NES and Super Famicom.

Moderator: Moderators

Forum rules
  • For making cartridges of your Super NES games, see Reproduction.
Post Reply
marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 1:46 pm

Hi! This is my first post, I need some help, I have a strange issue whit my SNES model SNES-GPU-02, Look the video with glicht or distortion in sound during the games, the video it's good, but the sound doesn't

https://youtu.be/VYv96SLGXNc

I made a bridge from chip L324M to de "positive" side of one capacitor, the distortion it's gone, but i missed one channel of sound, and some sound effect during the game doesn't listen!

Any HELP PLEASE!?

lidnariq
Posts: 10265
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: SNES sound distortion issue

Post by lidnariq » Sun Dec 13, 2020 1:56 pm

Get the schematic at https://wiki.superfamicom.org/schematic ... nd-pinouts

Using an audio amplifier, trace the audio path from the output to the DAC, or vice versa, and see where the distortion appears.

marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

Re: SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 2:10 pm

Sorry, I'm a rookie with all this! It's to hard reading the schematic ! I tought It was more easy to fixing

I Change the LM324 chip, and the AUDIO 2-CHANNEL 16-BIT D/A CONVERTER, and the issue still there!

User avatar
Fisher
Posts: 1152
Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: SNES sound distortion issue

Post by Fisher » Sun Dec 13, 2020 3:21 pm

Which pin of the IC you had put on what pin of wich capacitor?

The problem may be a bad electrolytic capacitor.
Since they're 20+ years exchanging them is a good idea.

There's also a small circuit with a transistor and some other components, that you can test with a small amplifier as Lidnariq suggested.

marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

Re: SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 3:40 pm

[img]https://drive.google.com/file/d/1R4mkQz ... ivesdk/img]


From pin 1 to the positive side of capacitor! The distortion its gonr but there are some missing sound, or sound glitches,


PF: After doing this, I replace all the capacitors and nothing happend,

User avatar
Fisher
Posts: 1152
Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: SNES sound distortion issue

Post by Fisher » Sun Dec 13, 2020 3:58 pm

Unfortunately, I'm not able to see the image that you have posted.
Looks like you are plugging the output of the left post amplifier to the positive of an output capacitor.
There is a big chance of some problem on the transistors Q16 and Q17 or on the circuit around them.

Have you tried another known good power supply, or even this one on a console that is working fine?
A bad one can cause many weird problems.
As you can see on the schematics, the VRef of this amplifier comes from a small transistor straight from the power supply.

It's also a great idea to do the tests that Lidnariq suggested and see if you can discover where the noise begins to happen, that will sure be a nice starting point.

User avatar
Nikku4211
Posts: 381
Joined: Sun Dec 15, 2019 1:28 pm
Location: Bronx, New York
Contact:

Re: SNES sound distortion issue

Post by Nikku4211 » Sun Dec 13, 2020 4:20 pm

Fisher wrote:
Sun Dec 13, 2020 3:58 pm
Unfortunately, I'm not able to see the image that you have posted.
I just clicked on it and I can see the image.
I have an ASD, so empathy is not natural for me. If I hurt you, I apologise.

marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

Re: SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 4:20 pm

I changed the properties now you can see the image.

I changed those capacitors, around the IC and nothing

My power supply its the same I used to in other SNES without problems

User avatar
Fisher
Posts: 1152
Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: SNES sound distortion issue

Post by Fisher » Sun Dec 13, 2020 4:48 pm

Now I can see it, thanks. :-)

Basically you had put the left channel post amplifier output on the right channel output capacitor.
I'm not sure if in this kind circuit is a good idea to do these trial and error stuff but, does it make any difference if you plug it on the C66 instead of the C65?

Again, I'm asking you to try the tests that Lidnariq said to try to narrow the problem.

marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

Re: SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 5:11 pm

I been tried with other capacitor, and nothing!
And I sorry I can't understand the schematic that the other user mencioned

I won't able to think that the IC of sound or cpu its damage!

User avatar
Fisher
Posts: 1152
Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: SNES sound distortion issue

Post by Fisher » Sun Dec 13, 2020 7:38 pm

As I've seem on your YT channel, your mother language is probably spanish, right?
The schematic is very well designed and simple to follow.
You can post your doubts here and I'm sure people here will be happy to help.

But try first to follow the signal with an amplifier, as suggested by Lidnariq.
This will give good clues about what is happening.

Looks like it's not related to the sound APU, probably just some problem with the post amplifier circuit. Since you've got no audio after bypassing part of the output circuit, that's probably where the problem lies, but it needs further testing to have a better idea of what's wrong.

marcorosa13
Posts: 9
Joined: Sun Dec 13, 2020 1:39 pm

Re: SNES sound distortion issue

Post by marcorosa13 » Sun Dec 13, 2020 8:02 pm

Thanks Fisher! Thanks a lot! Yes I'm from Argentina!

And I will try everything you said, to fix the console!

Can you check to my another post, about the another SNES I have with problems!

Post Reply