Avance Logic ALS100 Plus+ PnP OPL3 sound card for PC/104

Hey there,

I’m currently building a tiny DOS gaming PC and needed a sound card for it. Unfortunatly there aren’t many PC/104* sound cards available so I spun up my own.

*= PC/104 – Wikipedia, basically a form factor standart

Since I wanted a sound card that was compatible with most standards so I can play as many games as possible with it I desided on the Avance Logic ALS100 Plus+. The IC is pretty well documented what made designing the sound card much easier.

It’s features are:

• Adlib
• All Sound Blaster Pro applications
• All Sound Blaster 16 applications
• PC Speaker
• Sound Blaster ADPCM
• Yamaha OPL3 FM Synthesizer

That’ll cover every game I’m interested in. The PC speaker is mixed in with the audio out by the IC, that’s pretty cool.

The hardware specifications of the new sound card are as following:

Hardware specifications
• Software selectable DMA lines (0, 1, 3)
• Software selectable interrupt lines (5, 7, 9, 10, 11)
• PC/104 ISA Plug and Play bus interface
• DMA interface with FIFO
• Enhanced Game port
• 8-bit or 16-bit stereo digital audio from 4 kHz to 48 kHz
• 3D Sound Effect Processor
• FM/wavetable synthesis via OPL3
• Wavetable connector
• Stereo Line-Out

Design and development

If you’re just here for the design files and aren’t interested in the failures I’ve had designing the sound card just skip to the end 🙂

At first I took the specifications directly from the PC/104 consortium for the measurements: PC/104 – PC/104 ConsortiumPC/104 Consortium (pc104.org)

Then I read the manufacturer’s design sheet to build a sound card for the ALS100 Plus+ and added some minor noise cancellation.

First fail:

Yeah well, the IC is a bit bigger than a PQFP-100 (10% bigger to be exact). Meh. I tried to shorten the legs but ultimatively ordered another PCB. Bummer.

Second fail:

If you thought I would learn from my first mistake – think again! Yeah, so the OPL3 is also wider than a normal SOIC-24. This time I shortened the legs and soldered it down and went to testing (I shifted the IC down in the photo to better visualize the difference).

Third fail:

8bit- and 16bit-audio worked straight of the box so was the PC Speaker, but the FM synthesis was garbled. Staring at the schematics revealed another pretty stupid mistake:

If you havn’t spotted it yet: I switched around the adress lines. I cut the traces on the pcb and rewired them and FM synthesis was finally working.

Fourth fail (more like a foreseen issue):

There was a faint hum in the audio when plugging in a wavetable daughterboard. The soundcard has a digital and an analog ground which are connected at one point:

That’s fine and dandy – but the wavetable did just the same, so it created a ground loop. I removed the resistor on the sound card and the hum was gone 🙂

The dimensions for the wavetable daughterboard are approximately like this:

While testing I used a Dreamblaster X2 which fits nicely. Also pictured: The fix for fail #1 and an OPL3-clone.



Gerbers: Download
Schematics: Download
iBOM: Download
Drivers: Download
kicad symbol and footprint of the PC/104 board: Download
BOM* with links to mouser.com: Download

*= Missing from BOM:
• PC104-Connector, available on mouser.com
• OPL3, available new old stock from various suppliers
• ALS100 Plus+, unfortunatly EOL since the late 90s, so you have to desolder it from a working sound card.

4 thoughts on “Avance Logic ALS100 Plus+ PnP OPL3 sound card for PC/104

  1. Francesco Pontecorvo

    Congratulations. Lately I was just looking for a pc104 sound card for dos gaming, I finally got it on ebay, based on ES1869. If I had seen your project earlier I would not have bought it. Now I want to do this too, would it be possible in your opinion to use the ALS100 chip (non plus)? I have several and I could unsolder the chip.


    1. jensma Post author

      Hey there!
      Theoretically yes, but it wouldn’t be a drop in replacement, since the chip have vastly different pinouts.

  2. antonio

    I was so impressed by your posting.
    I’d like to make one, too.
    So I’d like to ask you a question.
    Can I use als120 instead of als100+?
    I look forward to your advice.

    1. jensma Post author

      Hey there! Glad you like it – unfortunatly I can’t find a datasheet or pinout for the ALS120 variant. So I’m not able to tell you if it is interchangeable or not.


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