I don't have that same model. I have the CT2890 Vibra16 S, which also has OPL3 and is PnP. It plays fine and dandy though. Didn't notice any issues with pitch or speed of FM.
It could be some electronic component going off the mark (crystal oscillator or a cap maybe?) Is digital sounding alright?

wbahnassi wrote on 2025-05-03, 22:29:

It could be some electronic component going off the mark (crystal oscillator or a cap maybe?) Is digital sounding alright?

Yes, my fear is that something is going on with the oscillator or a cap like you said... However, digital sounds perfect.
Man I was hoping that there was an easy solution, like a jumper that i didn't see ahah
Thank you for your reply!

The board seems to lack an onboard 14.31818MHz clock source and thus should rely on one from ISA slot, and it may not always be quite right although it should never be so wrong you have really noticable pitch difference... Do you have any other machine to test the card in ?

First thing that I did was test the card with Canyon.mid and Doom, since I know its music very well (also I'm a musician, I don't think I have perfect ear but I can tell when something is off).
Unfortunately the mobo that I'm using is the only one with an ISA slot that I've got.. Here it is: https://theretroweb.com/motherboards/s/dfi-am35-ec (with an Athlon 900 CPU)
Maybe the mobo is too "new"? Anyway, I'll try to record something later!

I recorded canyon.mid and Doom E1M1, you can find it here:

Canyon.mid: https://drive.proton.me/urls/KXVKA8ZCRG#b4nCDqPF2GNy

Doom E1M1: https://drive.proton.me/urls/AXZ2MPMFR4#vITQyh1Cm4TL

Awww that sounds cute 😅
I'm wondering if your mobo/BIOS settings are using a too high ISA clock. The BIOS settings should have frequency divider setting (or sometimes it's jumpers on the board). Try to use the maximum divider and see if it makes any difference.

Well, i tried the SB16 on another system (Pentium II MMX) and the issue is still there... guess it's really the card at this point 😁

So things to check easy:
* Proper voltage going into the OPL3 +5V on pin 1
* Proper clock 14.32MHz on pin 24 of the OPL3

I wonder, did they skimp on the extra crystals and use a not quite accurate divider or PLL.
The ratio between the 46.lots and the 14.3 and a bit is close to, but not quite 3.25 - - 3.25 would be 0.17% out

Matth79 wrote on 2025-05-08, 23:45:

The ratio between the 46.lots and the 14.3 and a bit is close to, but not quite 3.25 - - 3.25 would be 0.17% out

+0.17% is not something that would stand out that much. I'd claim that most people wouldn't actually notice it unless it is played at the same time as the expected frequency, and even in that case, it wouldn't sound "off tune" but just a slow beat (tremolo).

On the other hand, if there is a PLL for that and it is broken to use 3.0 instead of 3.25, you would actually get a shift of around a whole tone upwards (not quite, but "close enough").

wbahnassi wrote on 2025-05-05, 01:43:

I'm wondering if your mobo/BIOS settings are using a too high ISA clock.

The ISA clock (CLK) and the 14.318 oscillator pin (OSC) on the ISA bus are two different pins. ISA clock adjustment is not supposed to have any influence on the OSC pin. On many modern boards, OSC is driven directly from the reference crystal of the core frequency generator, while the ISA clock (unless you choose 7.14 in the SETUP) is generated from the PCI clock, which is generated from the FSB clock which in turn is synthesized from the same reference clock. So the ISA clock has one PLL and two dividers between the reference frequency and the actual clock, so a lot more things can go wrong there than on the OSC pin.