I did have a similar effect when I accidentally swapped the two crystals on a soundcard I built quite a while ago.
So, maybe it's worth checking if X1 on your card is the correct frequency. Sadly the picture is showing no markings on it, but I found a JAZZ16 card on Ebay that has a 16MHz crystal in that spot.

There is one other thing that could cause such an effect (which I ran across trying to mod an old XT with another crystal): if the soundcard is using any of the system's clock pins on the ISA bus and that's clocked too high:
Re: ISA clock rate

No idea if this card does, but if so, it might be worth checking the BIOS if those can be set with different divisions.

Of course, there might be totally different issues at play, it's just what came to my mind right now. 😀

MJay99 wrote on 2023-03-16, 22:39:

I did have a similar effect when I accidentally swapped the two crystals on a soundcard I built quite a while ago. So, maybe it […]
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I did have a similar effect when I accidentally swapped the two crystals on a soundcard I built quite a while ago.
So, maybe it's worth checking if X1 on your card is the correct frequency. Sadly the picture is showing no markings on it, but I found a JAZZ16 card on Ebay that has a 16MHz crystal in that spot.

There is one other thing that could cause such an effect (which I ran across trying to mod an old XT with another crystal): if the soundcard is using any of the system's clock pins on the ISA bus and that's clocked too high:
Re: ISA clock rate

No idea if this card does, but if so, it might be worth checking the BIOS if those can be set with different divisions.

Of course, there might be totally different issues at play, it's just what came to my mind right now. 😀

Thank you for your advice
I ordered a new crystal (was not expensive) since i don't have an oscilloscope at home to check the frequency. (well, i have one, but kind of broken)

(Edit: from pictures found online, it looks like it is a 16Mhz crystal)

I will check for the ISA frequency, but i don't remember seeing such parameter in the bios. And i tested with two different period correct motherboards.
If the new crystal does not solve the issue, i will try to borrow a working oscilloscope.

I received my 16Mhz crystal yesterday and replaced the old one.

No luck. I still have the accelerated and high pitched sound.

Should I replace the capacitors ? (Even if they looks fine. Mostly Nichicon)

Does your PSU provide -5V?

Certain sound cards need that in order to function properly. More details here: ISA Cards & Devices Requiring -5V

Joseph_Joestar wrote on 2023-03-21, 08:53:

Does your PSU provide -5V?

Certain sound cards need that in order to function properly. More details here: ISA Cards & Devices Requiring -5V

Oh ! I'm now quite sure that this is my problem.
Thank you very much!

I'm using a modern PSU. I've ordered a Voltage blaster.

This card shouldn't need -5V, and it wouldn't manifest in such a way either if it did. There would be garbled or otherwise distorted sound but it won't suddenly be wrong pitch.

Is the pitch twice as high or some different amount ? One thing this card needs is 14.31818MHz from ISA slot and on some motherboards this signal is not good enough or absent entirely. Is OPL2/3 music sounding correct or are only PCM sounds affected ?

Ok confirmed.
It was the missing -5V on ISA
I had an old PSU in my garage with -5V and gave it a try.
I generally avoid using old power supply but i knew this one was working.

Everything sounds fine now.

The Voltage Blaster will allow me to use a modern (and less sketchy) PSU

I was actually thinking exactly the same as Tiido and wouldn't have thought that a missing -5volts would affect much else than maybe an amp section.
But, under the link Joseph_Joestar posted, they're really listing exactly this phenomenon for a missing -5volts and a JAZZ16.

Seeing something new every day... At least I wasn't totally off with it being related to timing somehow... 😀

Tiido wrote on 2023-03-21, 21:06:

This card shouldn't need -5V, and it wouldn't manifest in such a way either if it did. There would be garbled or otherwise distorted sound but it won't suddenly be wrong pitch.

Is the pitch twice as high or some different amount ? One thing this card needs is 14.31818MHz from ISA slot and on some motherboards this signal is not good enough or absent entirely. Is OPL2/3 music sounding correct or are only PCM sounds affected ?

To be honest, power issue was the last thing in my list.

Yesterday evening I was super close to remove all capacitors to replace them. The soldering station was still hot after replacing the crystal. The only thing that prevented me to to so was laziness. I'm glad to be lazy

The link posted by Joseph_Joestar described so well my issue, with exactly the same card that i gave it a try.

I knew some cards needed that -5V but i though it was only exotic ancient cards. Not a quite common mid 90' sound card

Edit : well not exactly mid 90' (1993) but not ancient enough in my mind

Very interesting, I found photos of this card's backside and -5V line wasn't connected but perhaps there are revisions and they do funny things....?

Nice to hear things work now though ~