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ISA OPL2 Card

sergey

sergey

Veteran Member
Joined
Jul 15, 2010
Messages
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Location
Silicon Forest, Oregon, USA
Hi,

During some quiet time lately I've got bored enough to make an ISA OPL2 card. It is compatible (and closely follows) the design of the OPL2 card that was popular during late 80's and early 90's. So yes, all games that supported it works with my card too.

So I am wondering if anyone else is interesting in building such a card?

I still have two boards left (I ordered the minimal number of 3 boards at oshpark.com... They are US made, pink, and gold plated :)). And I will sell them for $20 each (that is the price I paid) plus shipping - $3 in US, $6 anywhere else.

But if there is enough interest I can place a larger order, in which case boards will be much cheaper... I guess $10 or so.

More details here:
http://www.malinov.com/Home/sergeys-projects/isa-opl2-card

Thanks,
Sergey

isa_opl2_board.jpgisa_opl2.jpg
 
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This seems to be an exact clone of the Adlib Music Synthesizer Card, 1990 revision, in about half the PCB space. There are the exact same number of resistors and capacitors, except the clock divider IC is different. Who has a metal drill to drill clean holes through the bracket?
 
I certainly like the idea and the initiative. The problem I've always had with a OPL2 clone board is you have to cannibalize another device to get the synth chips. Unless you have a non-working original, a cache of Yamaha ICs, or really really like grape-ape solder mask, the target users are limited without adding something 'more'.

There is an on-going project to accurately map the YM3812 with a shaved IC under a scope. A more full featured sound card with a replacement device might be the next step?


EDIT: NM, Turns out a log of Asia IC brokers have stock.
 
That's awesome. If there were enough interest to put together a kit, I would definitely buy one. That would save us all on shipping ICs from China.
 
Great Hierophant said:
This seems to be an exact clone of the Adlib Music Synthesizer Card, 1990 revision, in about half the PCB space. There are the exact same number of resistors and capacitors, except the clock divider IC is different. Who has a metal drill to drill clean holes through the bracket?
Click to expand...

As far as I know the 1987 revision was no different (except of PCB layout and 1/4" phone connector instead of 3.5 mm one). I didn't want to reinvent the wheel, and also I wanted to stay as close as possible to the original thing. The 74LS74 is cheaper, smaller and more available than 74LS109 used in the original card, and makes no functional difference.

I guess regular metal drill will work. But because the bracket is relatively thin, one can start with a small diameter drill, increasing it up to the required diameter. I have to drill my bracket yet, and I'll post the process and the drawing with exact hole positions and sizes.
 
The problem I have with both ebay and those recyclers are where did they get the chips? Unfortunately from destroyed boards. And it's demand that feeds their business and a replacement OPL2 card feeds demand.

I would rather group buy from a broker's overstock. But market's tend to work themselves out. I just personally hate it when I see 'working pull' in an eBay auction. :(
 
Hatta said:
That's awesome. If there were enough interest to put together a kit, I would definitely buy one. That would save us all on shipping ICs from China.
Click to expand...


I don't have any plans to do kits (too much overhead), but I can do PCBs. If you're interested in making kits, I can provide some guidance regarding ordering PCBs, or provide you PCBs for the manufacturing price + shipping.
Most of the components can be ordered from multiple distributors, and I have a BOM on my page for everything from Mouser except of OPL2/DAC, which can be purchased from China... shipping is not expensive $4 or so...
 
sergey said:
As far as I know the 1987 revision was no different (except of PCB layout and 1/4" phone connector instead of 3.5 mm one). I didn't want to reinvent the wheel, and also I wanted to stay as close as possible to the original thing. The 74LS74 is cheaper, smaller and more available than 74LS109 used in the original card, and makes no functional difference.

I guess regular metal drill will work. But because the bracket is relatively thin, one can start with a small diameter drill, increasing it up to the required diameter. I have to drill my bracket yet, and I'll post the process and the drawing with exact hole positions and sizes.
Click to expand...

While I could not swear that the resistor values are exactly the same in the 1987 and 1990 boards, the latter has two more decoupling capacitors than the former. http://www.wavetable.nl/?p=62
 
Sergey, not to hijaak your thread at all, but you folks that are interested in this board, Andrew Lynch and Per have had an OPL2 card on the burner for a test run for quite awhile. Though it appears that Sergey has done the build/test phase himself, and successfully.

Anyways - Lynch's thread is here. Layout of the PCB is here.
 
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Maverick1978 said:
Sergey, not to hijaak your thread at all, but you folks that are interested in this board, Andrew Lynch and Per have had an OPL2 card on the burner for a test run for quite awhile. Though it appears that Sergey has done the build/test phase himself, and successfully.

Anyways - Lynch's thread is here. Layout of the PCB is here.
Click to expand...
The only problem with that project is that the amplifiers are as bare bones as it gets. After looking at it for a while, I see that the project should have the following improvements:

1. A pair of proper Op-Amp buffers on the outputs from the stereo splitter.
2. A jumper that routed the ToBuffer output directly to the output amplifiers rather than through the stereo splitter (and of course corresponding jumpers to disconnect the outputs from the stereo splitter).
3. Proper filters and power-amplifiers for a solid output. Right now there's just a single pair of power-amplifiers tied directly to the outputs of the stereo splitter.

But besides that, it should be just fine. I don't think stereo-split mono is really any problem at all, but why have half the sample-rate when full quality output can be acheived by using the unsplit mono output. If anyone wonders why there is a Stereo DAC on an OPL2 board at all (as the OPL2 is mono), that's because the board also has support for the OPM and it's derivatives (OPP/OPZ/OPZII).
 
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Maverick1978 said:
Andrew Lynch and Per have had an OPL2 card on the burner for a test run for quite awhile.
Click to expand...

Yes, I am aware of that project. I prefer a more minimalistic approach of Adlib (OPL2 only with mono DAC-SS), and a smaller board. Anyway most of software (read - games) support just that. And I am also too cheap (or not a vintage collector enough) to spend ~$200 on the original thing.
 
Both designs could use power supply separation between the analog and digital side. A simple Pi filter on VCC and separate ground pours for analog decoupled with an RC would lower your noise floor on output. I always hated how noisy most PC sound cards were in the early days.
 
Separate ground planes for the analog and digital circuits would also be helpful in reducing noise. Just a few microvolts of noise injected into the analog gound plane can make an audible difference.
 
Great Hierophant said:
While that may improve the audio quality, that would distance the card more from that "classic" Adlib sound.
Click to expand...

Exactly :)

I agree with all these audio quality improvement tips, but:
1. I can't really hear any noise in from my board, unless I turn up the volume high while no music is being played.
2. It is not supposed to be a professional audio equipment (but rather something that resembles audio quality in good old days).
 
Why the OPL2? I recall when Intel brought out motherboards with the Yamaha OPL3-SA chips that they were roundly criticized for their cheapskate lousy sound.

I'm not a PC sound guy, so obviously I'm missing something.

Or is this like the local Craigslist seller who peddles 60's and 70's transistorized audio gear for exhoritant prices advertising true "vintage" sound. A friend had a 1960s Allied amplifier (germanium transistors) that gave truly awesome hiss, even with the gain turned all the way down... :rolleyes:
 
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