Very cool ! I do have some concerns about part choice. I see film caps that are in sound path, suggesting striving for superior sound quality, but at the same time everything is made with noisy carbon resistors and not metal film ones, and I think I'm seeing tantalums in audio path also which massively increase THD in analog applications. So I'm wondering what is the reasoning in the part choice. Small ceramics in sound path I don't know what type they are, but I surely hope NP0/C0G rather than X5R or such since other types lose a lot of capacitance as they get biased and are highly temperature sensitive and that increases THD dramatically once again.

How is compatibility of the OPTi chip ? I have a card with 82C928 which perhaps is newer by number, but it happens to have quite limited compatibility from my experience, with games not producing stereo or any sound at all so I wonder how the 924 compares.

neat :3

the video probably really doesn't do it justice though ^^ if you don't have any other means of recording you could use the mic-in on your camera if it has one maybe?

Only two tantalum capacitors are in the signal path. It's true that they could produce overtones or sound harsh, but during my tests I haven't heard anything bad. But I agree those two 10 uF parts could be replaced with bipolar Nichicon ES series parts.
All the rest of the tantalums are exclusively for filtering purposes in key parts of the PCB assembly (in some parts of the design, I abused overengineering).
The small ceramic ones are NP0 (most of them being between 27 pF to 470 pF), everywhere I could find them as such. The others are X5R .
Regarding resistors, I originally wanted to go with DALE parts. But for some reason I went with carbon resistors. Good thing is that I still have two spare PCBs and in the future when I will recover my electronics budget (sic) I will do another one with metal film resistors.

About the compatibility, the OPTi chip is running in Sound Blaster Pro compatibility mode. It doesn't have that annoying note hanging issue, fortunately. And it is easy to program. For the moment I am using generic OPTi drivers for MS-DOS but I am planning to write my own. There is even a project on GitHub of a guy that wrote drivers from scratch for OPTi 82c929 in a combination of Pascal/Assembly. I might contact him or peek into his source code. But the datasheet is pretty verbose in describing the programming of this chip.

I will try to do some recordings via the LINE-IN of my PC, it should capture the sound better.

A.

The effects usually aren't gonna be audible but certainly are measurable. But ok, very good. It is very nice to see new hardware being made ~
For opamps I suggest getting NJM4580 or equivalents from other companies, very high performance, lot of current capability and also cheap parts (not RRIO capable though, not sure if any part in the design relies on that).

Hanging notes are pretty much Creative's software based MPU401 implementation issue only, nobody else has such problem due to use of full hardware MPU401 interface. Good luck with the software, datasheet should indeed provide everything necessary, assuming there are no oddities about order of operations etc.

Yeah the Guy is Jan Knipperts and already registred here at the Forum, he is named DragonSphere
And also helped a lot with Tandy TSR and currently developes the Tandy Tracker.

Nice work, i like the OPTI Chips.

Thanks Tiido! I will take a look at NJM4580. By the way, I am using a NJM2100 but only for the FM DAC. It was readily available on Mouser and cheap enough. The SE5534A is quasi-unobtainable (but I had 4 NOS in my parts box, so I used them) but easily replaceable with NE5534A -- which is cheap. And the other ones that I used MC33078P are quite expensive for my tastes but I used them in the past with good results.

Yes, indeed, it's Jan Knipperts! I looked a little bit over his source code (I am very familiar with x86 assembly and Pascal) and it is well made. It can be easily modified to also support OPTi 82c924. I will try to kindly ask him if he would like to do the update himself. Otherwise, I will fork his work and add support for 82c924 myself. Then again, I might just write my own driver from scratch (it wouldn't be the first time, though).

looking good!
components are so neatly placed!

Thank you!
I really enjoy designing hardware and PCBs layouts. Especially when I am designing the hardware that I wanted and never had any chance to have back in the '90s.

4580 is sort of japanese version of NE5532, with very similar performance (except 4580 has much higher output current capability). 2100 is a toy compared to those and the MC33078 is inferior to 4580 and 5532 also.

What are the 5534 used for ? It isn't normal to use single section opamp unless you absolutely need offset correction feature or are really pushing thermal limits...

I used NJM2100 for the YAC-512 converter, between the AOUT and SWIN pins. Indeed I might just reconsider using a better quality OPAMP in this position.
SE5534 are individual output amplifiers directly connecting the CODEC left and right outputs to the line out connector. I just had them in my drawer and wanted to use them for a very long time.

This looks really cool. I’d definitely enjoy building one, given the chance.

- Alex

Looks gorgeous. A properly engineered bit of kit. It's kinda sad to think that those OPTi chips were resigned to bargain-basement designs and not a proper high end board like this where they could really shine.

Those board shots are wonderful 😀 I didn't realise you posted on here, I think your website is fantastic for all the write-ups on your other PCB designs.