PAL snes audio anomaly

[Dedly1]

Hi,

I've got a PAL SNES snsp cpu-01 or 02 model with a bizarre audio issue.

The game Earthworm Jim 2 either on everdrive or a repro cart tested so far has a very strange crackling popping when sound effects are played.
Music is fine.

I've run the Burn in test and several other bit roms, all show PASS on each section.
Ive tried the NTSC USA version rom as well for a laugh, audio is even more messed up.

From the hundreds of games tested so far, this is the only one so far with ear bleeding scratchy popping at random or more problems if a different region is used.

I do have a new VReg and capacitor kit inbound for the SG and SN to be installed as soon as practical.

Any idea what this is?

Thanks.

 

[Ferris1000]

it could be multiple things, could be a faulty filtering capacitor or a faulty sound chip.

 

[Dedly1]

Well I've had the console run a few BIT programs for several hours all with a 100% PASS.
I guess i could rule out the hardware at least?

Is it not odd that it's just this one game though? unless there's another game with similar sound driver to ewj2?

I'll chime in again once i get the caps and Vreg installed.

 

[Ferris1000]

It's still possible that the Soundchip is marginal, it might sound right to you in most cases but it doesn't fully function as expected.
I saw this dozen of Times on Commodore 64 where the SID chip works and outputs sound but in some cases it doesn't sound quite right.
To make it more understandable: Those Soundchips have Multiple Voices and Filters, if one of the Filters as an example doesn't work correctly the Sound might sound Distorted, quiet, make a pop sound or similar.

This happens sometimes, to rule out this issue I would try the Game on a different SNES Console to verify the Source of the Problem.

 

[JaapDaniels]

It's still possible that the Soundchip is marginal, it might sound right to you in most cases but it doesn't fully function as expected.
I saw this dozen of Times on Commodore 64 where the SID chip works and outputs sound but in some cases it doesn't sound quite right.
To make it more understandable: Those Soundchips have Multiple Voices and Filters, if one of the Filters as an example doesn't work correctly the Sound might sound Distorted, quiet, make a pop sound or similar.

This happens sometimes, to rule out this issue I would try the Game on a different SNES Console to verify the Source of the Problem.

Well I've had the console run a few BIT programs for several hours all with a 100% PASS.
I guess i could rule out the hardware at least?

Is it not odd that it's just this one game though? unless there's another game with similar sound driver to ewj2?

I'll chime in again once i get the caps and Vreg installed.

The snes has no self test hw, so test software can only see short circuit or open circuit as a failure, teh other problems are diagnosed by listening, viewing and pressing buttons.
since you've got sound functioning partly, no test program will help you further, you can however feed it constant SFX signal and use a scope to really go down the rabit hole.
I do however rcomand replace all through-hole caps for they're far past thier date by now, and it might already be the fix.
The processor might need resolder and a clean up.
And please don't use any hardware mods for they tent to alter more than they fix.
ooh, almost forgot, replcae the cables to your tv and to your speakers, for they might be worn.

 

[Ferris1000]

Right, caps could also cause distortion, but a marginal Soundchip would also not be detected by any Hardware test and only someone who often works with a specific Computer or Console and/or listen to specific tracks knows how they should sound and would notice even slight differences.
The best would be if you test the Game on a different console to compare and make sure that it's not the Rom / Cartridge.
I'm not familiar with Earthworm Jim 2 and how it should Sound so that's why a direct comparison would be the best test to isolate the Problem to your specific console.

A faulty cable would only cause loosing sound or hum but not crackling popping when sound effects are played.

 

[JaapDaniels]

Right, caps could also cause distortion, but a marginal Soundchip would also not be detected by any Hardware test and only someone who often works with a specific Computer or Console and/or listen to specific tracks knows how they should sound and would notice even slight differences.
The best would be if you test the Game on a different console to compare and make sure that it's not the Rom / Cartridge.
I'm not familiar with Earthworm Jim 2 and how it should Sound so that's why a direct comparison would be the best test to isolate the Problem to your specific console.

A faulty cable would only cause loosing sound or hum but not crackling popping when sound effects are played.

Crackling could come by using the coax connection for both sound and video, when shielding isn't isolated from signal.
The only wierd thing is SFX does this while music doesn't, as far as i know most cartridges uses the same process for SFX and music, except for super gameboy like stuff.
Now i know the https://8bitmods.com/snes-spdif-digital-audio-upgrade-mod/ can actually cause this problem for it's a bit too direct reacting and unfiltered.
I'd say caps redo and a good cleanup on all contact points with either contact spray, or pure alcohol.
And for the cartridge slot to clean with: https://www.1upcard.com/collections...g-cartridge-by-1upcard?variant=31439439855682

 

[Dedly1]

Ok, So I've replaced all the caps on the board, only 1 through hole, rest were smd.
Aside from the display being notably! cleaner, the sound issue with this one game remains.

I do have a spare Vreg, but this one seems ok no buzzing etc.

Thanks for the note about the BIT not giving any insight to a potential issue other than on or off.
I hear zero issues while test is running.

Of the hundreds of games tested so far, only EWJ2 persists a random pop&crack and only with sound effects&voices.

The pop crackle does sound something akin to messing with audio cables.
Jims voice will at times sound like a sega md/genesis trying to talk to you

Emulators seem to not like this game and weapon lord in particular.
Although WLord works fine on my snes.

The only real difference with audio from the console in general is volume attenuation.
Some games louder/softer but this is how it was, nothing unusual there.

I have cleaned the cart port rigorously, however I will also pull the port off drown the pin holes and poke it with a brush.

It would seem unlikely that its just that 1 pin that messes audio up with that 1 game, and not show anything elsewhere. However....TBC

The only only thing i suspect barring a 1% failed dsp chip/s is a potential timing issue.
If i try the NTSC USA rom, the game will make clicks for sound effects much like an emulator with issues (zsnes).

I have no idea how to test the oscillator for an ok, but based on how bad emulators have it, and how my snes reacts to a rom switch for THIS game, there might be something here.

For other NTSC USA/JAP games, this hasn't been an issue other than speed/resolution/refresh.
No problems whatsoever.

I can't stress enough how otherwise problem free this system is.
just that one game?

Is there a site with information regards the sound driver method used for the game, perhaps there's another game that uses the same library, to give me the same problem.

Thanks.

Edit: pulled the cart port and IPA/deox no change.

 

[Dedly1]

Right, I found another archive @snescentral with a few BIT programs to try.
And there is indeed a problem found this time, good!

The program failed was Test_timer_speed_#123 and a few others that test the SPC700.
I get the first two lines and then it stops.

All other BITs check out ok.

There is allegedly a ceramic resonator somewhere on the snes which has something to do with sound, is that right? could it be this thing?

Without a scope i can not test the oscillator, but i'll just replace it and try anyway, again i would've expected some strange results from other games.

 

[Dedly1]

Found a thread where the OP had what seems like the same problem or something very similar.
OP supposedly solved/workaround the issue by using something called a "Universal cartridge"

If anyone has an idea of what components this cart has that also happen to show up on the snes mainboard, please let me know.

I really don't want to have to trash or harvest an otherwise working system.

Thanks again

 

[Dedly1]

Well I've replaced the ceramic resonator with an smd part. no change.

For what it's worth, I used a small scope on the original part with various tragic results.

It would appear that even probing this part made the snes allergic to a point where it would potentially not even boot the game if the scope/probe was dialed in a particular way.

In either case this would make the sound effect problem a LOT more pronounced if touched at all with the probe. Not able to get a usable reading.

Another strange thing to note, the issue seems? to be temperature sensitive perhaps maybe?

If the system is left on for time enough, the sound issue almost fixes itself, well it gets better.
Conversely, if the snes is cooled rapidly, the sound issue gets really bad.

I did get another snes to try and an oem version of the same game just to be sure.
Got lucky and scored a 1-chip variant.

This one also seems to have a .1% fringe case of the same issue, but to a MUCH lesser degree, not surprising considering it's a later model.

Ferris1000 you mentioned a marginal IC being a possibility with the SID on C64.
With these issues wouldn't the sound output be less random and more specific to the signal at time, more consistent ?

Thanks.