This is inspired by the video Using an old 8 bit ISA sound card (Roland LAPC-I) without a PC.

I would like to find detailed instructions (for those unlearned in electronics), including a parts list, to replicate the setup in the video, which includes something to the effect of:

  • ATX power supply
  • wires
  • wire couplers
  • external ISA bus
  • USB-to-MIDI adapter (readily available)

And improvements would be welcome, such as, if possible, a more compact power supply and more elegant wiring to facilitate enclosure of these components with the card.

Operation in Windows 10/11 would suffice but Linux support would be ideal, although this would probably require a kernel module, if emulators such as ScummVM and PCem could use it.

The closest alternative of which I'm aware is the usb2isa-r by ARS Technologies, although price and support may be obstacles.

  • 3
    Getting a detailed list would be over-engineering, as this is just a fun hobby project that can be made with random parts lying around. Any power supply, wires, or USB MIDI adapter will do, as long as they work. They even seem to use a low quality MIDI adapter which I believe is made against MIDI specs as it might omit the optocoupler. It is impossible to say how much current the card needs so as long as it's powerful enough. The only difficult bit is to find the ISA slot connector for supplying power, some people find old backplanes or desolder it from a broken motherboars.
    – Justme
    Commented Aug 8, 2023 at 6:05
  • Those familiar with the parts and process might consider this a fun project. Everyone else would need additional instructions; for instance, the names and specs of all the components and assembly instructions, which isn't over-engineering. Commented Aug 8, 2023 at 23:37
  • To be fair, what would be the purpose of using the card outside a PC with wires dangling dangeroulsly and any mishap burning a good sound card? Use an old PC, put the card in, turn power on. Don't use the PC, no disk drives, hard drives or OS needed, no other cards either, no monitor or keyboard. The sound card would not see any difference, and you have a metal/plastic box with compatible power supply and compatible socket/slot for the sound card.
    – Justme
    Commented Aug 10, 2023 at 11:16
  • @Justme I definitely +1 to that, especially given the rarity and price of an LAPC-I and MCB-1 these days. :)
    – 640KB
    Commented Aug 20, 2023 at 0:24

2 Answers 2


According to the video description, the creator of the video

connected only to the +5V, -5V and ground lines of an ATX power supply

If you are, as you write, "unlearned in electronics", I'd recommend a slightly different approach:

  • Get yourself a dedicated +/- 5 V power supply with no minimum load. Many PC power supplies require some minimum load on at least one rail, which may be a source of problems you don't want. A good choice might be the Mean Well MW RT-65A, which is readily available and also provides +12V (which you don't need for this setup, but might need with other ISA cards).

  • Get a passive ISA backplane like this*, which should take care of all the soldering for you. Connect the power rails to your power supply.

  • Connect the sound card to your modern PC using a USB to MIDI adapter.

  • Connect active speakers or an amplifier to the sound card.

There also seems to be a Midi Connector Box in the video, presumably used as a passive adapter to connect the PC's MIDI out to the card's MIDI in. Depending on what MIDI cables you have at hand, you might need that, or some other kind of passive adapter, as well.

And that appears to be it. Which operating systems are supported depends on your choice of USB to MIDI adapter; the card works a MIDI expander in this context, not as a sound card.

Good luck.

* I'm not affiliated in any way with this particular seller, nor am I familiar with this specific product. It's just an example of what to look for. I chose this as an example because it's comparatively small ‒ you need only one slot, after all ‒ and because of the screw terminals for power.

  • 1
    Such components are the types of improvements I seek. Thanks! Commented Aug 8, 2023 at 23:44

Michael Graf already pointed out the basic way to get it working, so here a few additional information bits about the LAPC-I that may help to understand the setup involved:


  • It's mostly known that LA stands for Linear Arithmetic (Synthesizer)
  • Unlike assumed PC stands not for Personal Computer but
    • P complements LA as Processor, while
    • C simply stands for Card.
  • Similar is I not not the Roman numeral for one but the letter 'I', for IBM-PC.
  • Thus LAPC-I means Linear Arithmetic Processor Card for the IBM-PC

Whats In It?

A LAPC-I is essentially the combination of a

  • Roland MT32 Multi-Timbral sound generator
  • Roland MPU-IPC-T - MIDI Processor Unit for the IBM PC - which is a combination of the prior
    • Roland MIF-IPC - MIDI Inter Face for the IBM PC - with all of the
    • Roland MPU-401 breakout box except for the connectors

MIF cards were available for many common computer, especially Japanese systems, but also C64 or Apple II. They 'only' provided the MIDI interface, all further electronics were part of the MPU-401 box. The MPU-IPC-T moved much of onto it's card reducing the break out box size.

The MT32 in turn was the syntesizer to be controlled via MIDI. It was considered a 'low end' offering for 'Hobbyist' musicians.

The LAPC-I integrated all of that onto one board needing only the smaller break out box (now called MCB-1 - MIDI Connector Box), as seen in above picture, to support connection with other MIDI devices (Manual).

Why Does It Work Without PC

The MT32 is a stand alone synthesizer controlled over MIDI. It does not need a PC to work. The PC's MIDI interface part will when only powered be strictly invisible to the bus - as shown in the manual:

enter image description here

(From the LAPC-I Manual p.24)

All input at MIDI-IN will be handed to MIDI-OUT and thus the MT32 part. For all that matters it will look and work like any stand alone MT-32.

How To Connect

The LAPC-I became famous for high end gamer setup - and that created one problem for today's usage: Gamers almost never bought the MCB1, which was sold separat. Thus the MCB-1 is a rather rare sight.

But since the connector used (DA-15) is a common one and the MCB-1 insides known a rebuild shouldn't be too hard.

enter image description here

Alternative Solutions

Get Yourself a Standard MT-32 Box.

While 'hacking' a LAPC-I to work as a stand alone MT-32 is nice, it involves a lot of work and at least basic electronic skills if no MCB-1 is at hand. In contrast any MT-32 will already include the necessary connectors, reducing the task to getting an USB to MIDI interface and plug it into PC and MT-32. No ISA setup, no external power supply, no soldering, just plug and play :))

Also, MT-32 are way more common and available at way lower prices than a LAPC-I.

Still Insisting to "Hack" it?

Well, as a quick look at some of my LAPC-I

enter image description here

shows, it connects only

  • GND - at B1 / B10 / B31
  • +5V - at B3 / B29
  • -5V - at B5

for power. Thus a simple 62 Pin Card Edge Connector at ca. USD 2, a +/-5V PSU of your choice (*1) and 6 wires connecting those two will do it.

While it's really a little fun job, I would still suggest to be careful and count everything twice - at least.

*1 - Quickhack would be to chain two cheap USB wall warts.

  • The LAPC-I is more like the CM-32L than the MT-32 due to the extra SFX in channel 10. Additional context and alternatives are definitely worth noting for others' sake, including this resource: Roland MT-32 CM-32L CM-64 CM-500 Ultimate Tutorial. But I'm not looking for alternative beyond that which I've stated. I would enjoy at least trying to use my LAPC-I and MCB-1 again in this way. Commented Aug 8, 2023 at 23:15
  • @ParticleMan no need to get snarky, especially as your question does not note what your information level is. This includes not mentioning that you're already posses a MCB-1, as that reduces the task to simply adding power to the LAPC-I. Location can be easy derived form any of the many ISA pinout mappings out there.
    – Raffzahn
    Commented Aug 9, 2023 at 2:10
  • No snark intended. My request for instructions for those unlearned in electronics includes myself. The additional "hack" info seems to cover much ground (pun intended)—Thanks! The two wall warts would be +5V and -5V, respectively? But it remains unclear how this would be done. Commented Aug 9, 2023 at 2:35
  • @ParticleMan Information given is a gift, not really great o complain if one doesn't like the colour of it. Also, no, both delivering 5V. By chaining them they deliver GND/+5/+10, which is the same as -5V/GND/+5V. Relative values are always based on the reference used. Don't take it personal, but if your knowledge is that restricted, you may not want to follow some advice "from the net". Use either a fixed setup like that USB to ISA or let someone do it for you . A working LAPC-I is quite valuable these days, way more than that ISA-USB thingy - which also can be used for more excitement.
    – Raffzahn
    Commented Aug 9, 2023 at 12:32

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