VOGONS


First post, by Shreddoc

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Forgive me if this thread already exists somewhere, but I can't see it. After completing a modest version of such a build last weekend, I thought there must be many of us doing this sort of thing, and it would be nice to see them gathered in one place.

Obligatory crappy photo:

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I wanted to do it cost-effectively, by re-using things I already had. Therefore I limited my purchases to an RPi 3A+, and a $3-including-shipping 5102 DAC from Aliexpress. A total outlay of <US$50.

The recycled Case : A shithouse ($10-20) Aliexpress amplifier I got for testing some time ago - it's case, while nothing special, is the most worthwhile piece of the whole deal, the electronics being rubbish. Semi-gutted it, by depopulating all it's boards components.

But I left the bare board in place, so I could re-use it's external fittings such as switch, power input socket, and 3.5mm audio socket - saves me needing to rebuild my own. I drilled the old board out at a handful of strategic places to ensure signals from those re-used ports couldn't wander through the old board. Then layered a thin piece of wood over top, onto which the RPi was secured.

Power was wired from the case's DC input socket, directly to the back of the RPi board - the PP2 (+) and PP5 (-) solder points - via the case's switch. This way, I can use any-old of the many 5V 2.5A DC power bricks I have lying around from my Pile-of-ADSL-routers years, rather than having to spend more hard-earned on a special Pi-USB3 power brick. The Pi's audio out is similarly wired to the case's 3.5mm socket.

A USB extension cable neatly coming out the back of the case provides a port for my existing MIDI-USB cable, which shares my DOS PC's MPU with my real SC-55 by way of a Serdaco DB15 splitter.

I have not bothered with extra switches or even screen functionality, as those are not important to me - I simply wanted a tidy, convenient physical box that I can easily switch on when I need MT-32 sound.

Job done. Nothing special or fancy in any way, but I'm really pleased. And very thankful to Dale Whinham, the author of mt32-pi, and indeed to the makers of the excellent RPi itself, and to Roland for making such a great device in the first place, and to the skilled composers of the MT32 soundtracks we all love, and which I finally (after 30 years) get to fully experience in a fun, convenient way.

THANK YOU!!! 😀

Reply 1 of 8, by Thermalwrong

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That's a nice clean design, I do recommend that you consider adding buttons though. Otherwise you can't switch from MT-32 to soundfont mode, unless maybe you use MT32-pi-control software.

Here's what I've been working on for a few weeks now - my MT32-pi case which is designed to look like a shrunken regular MT32, but with the bigger 20x2 LCD.

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IT's been designed in Fusion 360, but the DAC and MIDI input PCB are currently just on some PCB stripboard that I knocked together. Digitising the physical objects is time consuming work, especially when a print of the top and bottom parts takes 6 hours each. The DAC's audio jack doesn't fit right for instance, but it's close enough to work.

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The Pi3 is screwed in there to be an MT-32PI forever, but on the underside I can get to the micro SD card to swap it out, and the MicroSD card can't fall into the case (very annoying when that happens).

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The front wouldn't look right with the 3d printing layer lines, and my attempts to print text with the 3d printer didn't work out, so I used my Brother QL700 label printer to print out the matte paper label, and the glossy plastic label. The end result looks pretty fantastic to me, but I'd love it if there was a better way to print the matte front part. I Was thinking maybe a PCB with no traces on it, in a black matte finish. That would be cheap-ish and the silkscreen would work perfectly for the button labels.

Something I'd like to look at next is making a PCB that doesn't sit on top of the CPU so it can cool better, there's room in the case for that. But this one works and I can use it now 😀

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Reply 2 of 8, by vutt

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Excellent thread. Dale deserves more publicity for his outstanding work on github.com/dwhinham/mt32-pi

I have to admit it is little embarrassing to post mine after Thermalwrong professional work above, but here we go...
I consider this work in progress. Needs a paint job and proper labeling.
I had old unused TV set-box laying around. Entire implementation is based on goal to reuse it. Not only box itself but also part of unit old motherboard mainly for convenient barrel jack for power and RCA ones for audio access. I left all controls for back side because I wanted to keep front side stealth clean look.
I'm using it in tandem via Yamaha MU50 midi pass through connection.

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Guts

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Back

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Proof of concept of LCD bleed light utilization.

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I'm still waiting for sd card extension cable to arrive so I can extend convenient SD card swapping capability to back.
If it turns out not to be stable solution I will probably cut out access bay for SD card access from bottom.

Reply 3 of 8, by Thermalwrong

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I meant to say in the 'what retro' thread, I think your one looks really excellent too, the backlit logo is a really nice effect 😀

Also, seeing your one all put together spurred me on somewhat, this has been brewing since mid 2019 when I found out about WavePi, then MT32-Pi.

I use an SD-card extender cable for one of my PC builds and it's been working just fine with that, I think the protocol it uses is fairly tolerant of extension.

For anyone wanting to make custom labels to match the MT32's font, there's a free truetype font called TR909 that seems to be perfect for the era of Roland products it's from.

Reply 4 of 8, by ratsflif

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I've been meaning to post some pics of mine for a while. I have an old IBM Pentium 90 that ive been using for Dos gaming. I installed an ESS Audio drive sound card and built the clumsyMidi interface board with a break out screen and buttons. I modified the cover for the lower drive bay with the use of a dremel and then wired the Pi and all the connections internally. So now the MT32-Pi boots up with the computer and I can control the soundfonts from the front panel.

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Reply 5 of 8, by Ulfenknulfen

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Here my little Project:

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greetz
Ulf

Reply 8 of 8, by Jo22

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newtmonkey wrote on 2021-04-15, 10:29:

Really nice builds in here, all around. But I especially like ratsflif's build, a 5.25" bay mounted MT32 is such an awesome idea!!

Ditto.

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I couldn't be wrong, but I think some semi-professional soundcards stored MIDI daughterboards (WaveBlaster, DB50XG etc) in the bay.
The Terratec/Promedia EWS series was among of them, I believe.

Anyway, this is no critique. I simply mean to say that ratslif's approach is professional! 😎

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