Davo
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Posts posted by Davo
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I'm working on a design for a quad SID midibox. Right now it's still in the design phase, but it'll have everything you need for a full control surface quad sid synth on one board. I've added a simple mixer to provide a mono output. When the board is finished and tested, I'll release foil patterns. A note of caution: I don't reccomend making a board from my patterns using an iron and transfer paper unless you know what you're doing. I had a horrible time getting even a halfway decent transfer with an iron. I'll be using a hot-roller laminator to do my tranfers from now on. .032" board is also a good thing to try. It cuts a lot easier than regular .062" board and can be run through an unmodified laminator.
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From the referenced page:
I'm unsure if I ever require the PWM output for a future extension, that's the reason why the oscillator option is provided.I read this as you saying that the 1MHz output is there because you had room for it in the core MIOS code and that it might be removed in the future to make room for something else.
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CV means "continuous voltage". That is, a constantly varying voltage is used to control various parameters of a synthesizer such as oscillators, filters, and envelope generators. Poke around http://www.synthesizers.com and you'll find some more in-depth descriptions and examples.
The AOUT and AIN modules allow a Midibox device to control and be controlled by CV signals. A big reason why the AOUT module exists is because running the output of an MBSID through a Moog-style ladder filter results in VERY VERY nice noises. Think of these sounds: "Ooooo... Wahhhhh... Ohhhhhh... Eeeee...". You'll hear something like that when "opening up" a ladder filter while a sound is going through it. Now, you can control how "open" a filter is with a knob, but it's easier to set things up so it opens and closes the same way for every note. That's what the CV input to a filter is for. The shape of the graph of the CV going to the filter determines if you'll get something that sounds like "BOWDUNG", "VOOP", or something else.
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Something like that sounds easy to make in a decently-equipped metal shop. A standard box-and-pan brake seems appropriate.
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I've never owned and only very rarely played with a Megadrive/Genesis. What is the sound of YM2612 like?
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I'm seeing if I can come up with an all-in-one board for implementing a quad midibox SID. My design software (geda) is throwing fits over oscillator module footprints, so I thought I'd try implementing a 1MHz oscillator using just a crystal and support parts. I remember seeing somewhere a schematic that uses a crystal, a couple resistors, a couple capacitors, and a transistor to get a 1:1 pulse train. Can someone show me something like this?
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While sequencer tricks can mimic "super poly", I'd very much like it implemented because it'll be very nice for live performances.
BTW, Modularman, have you completed that six-way VCF design yet? Is it a real ladder filter?
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GreenTRF isn't paper, but a pigment powder of some sort on a thin plastic carrier. I'm looking at the docs for the transfer paper and it says that the varieties of TRF are green, white, metallic (several colors) and clear. The clear TRF is for making soak-off and dry-rub decals. That's probably most appropriate for doing front panels. With a color laser printer, the results should be very nice. I'm now sure how to get white on such a decal though. You could probably lay down your backgrounds directly as if you're going to etch the front panel, then apply WhiteTRF. Then put a decal using ClearTRF over that. See http://www.pulsar.gs/ for more info.
I don't see why green or white TRFs can't be used with the Gootee method. They adhere to toner fused to metal, which is exactly what Gootee's method results in. For soak-off and dry-rub decals, you need the special gluey coating that Pulsar puts on their transfer paper. That glue is washed off when using it to make circuit boards.
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Yes, it's a laser. My first try with this paper was on a Laserjet 4050. I got much nicer results with the Xerox, however that may have been just because it was a second attempt.
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I'm aware of the Gootee site and I've been trying what I see there. The stuff I'm using are TTS paper and GreenTRF from Pulsar. TTS is designed specifically for this application, but is quite expensive at $1 or so per sheet. I bought it shortly before I found Gootee's site. The printer I'm using is a high end Xerox Phaser of some sort used for graphic arts at the local university.
I'm considering using the stuff Gootee uses to see if that works any better. There are not Staples places where I live, so I'll try one of the listed substitutes. GreenTRF is a sealer that's ironed over the toner to give a very tough mask. There are other TRF types such as white for doing "silk screening" for the parts side of a PCB. There are others for other purposes.
Now for a critique of this TRF stuff. If you look at my foil patterns, there are some very wide areas. It might have been my technique, but there were pinholes in the green stuff on those wide areas. For the narrower parts, where I managed to get nice and sharp edges with toner here and there, the green was nice and sharp. It covered all the unavoidable unevenness and pinholes in the toner and looks a lot like real silk-screening. Applying full pressure from my fingernails, I cannot scratch it either by tapping or scraping. It's somewhat, but not really resiliant against getting banged with 1/4" plugs and MIDI cable ground shells. Since the green stuff was meant to be removed with acetone, that may or may not be a concern for using it on front panels. It might complicate spraying laquer over it too. I don't have any other TRF types, so I can't comment there.
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Can I get some advice from someone who clearly understands how to use toner-transfer paper? Some time ago I posted something about making a simple mixer to mix the four outputs from a Midibox FM or a quad SID to a mono output. I entered the schematics into Geda (href="http://www.geda.seul.org) and routed the PCB traces using PCB (same page). I exported the foil patterns to Postscript format and with LaTeX made a full sheet containing some foil patterns I want to print out on the toner-transfer paper. The resulting PDF can be found here http://www.cs.csubak.edu/~dgriffi/stage1.pdf. The mixer is the smaller pattern printed three times on the lower half of the page. The top half contains two copies of a two-sided board pattern for some mods I plan to apply to my Paia Fatman.
Would someone please take a look and tell me if there's anything wrong with the artwork. How hard should I press? How long? How hot? With or without a sheet on top?
After blowing one sheet, I found that rubbing instead of simply pressing helps get things bonded, but I still keep getting lots of broken traces. I'm about to sell this stuff off and go back to the photographic process.
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I was under the impression that CEM chips weren't made anymore. Am I wrong or are these new-old stock pieces?
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PICTURES!!!
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I see those synths on Ebay all the time. What are they like?
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I'm in the middle of a multiple-stage hypermodification of my Paia Fatman. The first stage includes stuff that requires only one toggle switch, one pot, or less. Those will be mounted where the front-mounted jacks used to go. Two of these is a VCF expansion that gives a more moogy 24dB/oct and a VCF input jack. If I can figure out how to implement a simple gate and pitch output on the SID and FM synths, that would take care of my desire for a VCF for a while. According to the schematics, it looks like I can simply plug those CVs into the appropriate jacks on the Fatman.
More about the modifications, it seems like the Paia Fracrack is an ideal platform to mount further mods. It might even be nice for assorted knicknacks connected to midibox-based synths.
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Something I was mulling over today was a reinterpretation of the keytar and this thread seems to be the right place to do a brain dump. The MBHP seems like just the brain to run it.
Suppose we start with a wooden base (I like poplar). Mount four or five octaves on it. The neck would be a hollow aluminum bar bolted just behind the keys and is done so in such a way that it can be easily flipped around to make it left-handed. The neck contains a ribbon controller, expression bar, buttons, dials, and so on much like the Roland AX-7. Screwed over the neck and behind the keys is the control console. Here are a numeric keypad, LCD display, and patch buttons, and perhaps some assignable sliders.
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This calls to mind a similar question. Jameco #230535CC is a 25-watt triple output supply for about $24: more or less perfect for a Midibox synth. Since it's regulated, I removed the voltage regulator. I then noticed the voltage drop and decided to omit the rectifier. After all, it's not like I'll be constantly messing with the inside once I get it up and running. Then I noticed that big capacitor. Do I really need that 2200uF there now that filtering is taken care of by the regulated power supply? It's not a big problem now, but when I get to work on my SID machine, considerable useful space will be saved by omitting these eight caps.
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This sounds nice, but how would one interface it to a Midibox SID or FM? I'm thinking of building one for my Paia Fatman.
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Hmm.. Yesterday I came across this site: http://www.colinfraser.com/m2d/m2d.htm, which details a much simpler way to convert midi to sync-24. All told, it uses a PIC 12F629, an optocoupler, six resistors, one capacitor, and two midi-style jacks.
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I've been looking at the Prophet64 setup and I'm wondering where I can get a sync-24 converter. This seems like something a Midibox core module could handle. Anyone here know where to go from this point?
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Suppose I have Midiboxes SID and FM, and a Paia Fatman or two in a rack. Together they have a lot more outputs than typical keyboard amps have inputs. The obvious solution would be a simple 12-channel (or so) mixer in a 1U package. The controls would be level, panpot, mute, and a master output level with maybe a headphone output. The output would then go to a guitar amp or two, easily and cheaply available from a pawn shop. I've yet to see an amp intended for keyboards in the local pawn shops. The summing amp circuits discussed when I brought up adding an internal mixer to a synth sounds like a good place to start. Opinions?
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Sounds like impatience. Plaster should be cured for at least a day and kept slightly damp after it sets. Mist it lightly, then put plastic over it. It should be very difficult to scratch cured plaster with a fingernail.
Here's another idea borrowed from makeup. Foamed latex prosthetics are very realistic, but can be used only once, are costly, and it's a difficult and long process. A much cheaper and easier way is called shell latex. It works well for stage, but looks funny for extreme closeups as in film or TV. For this technique, you omit the inner piece and instead paint liquid latex around the inside of the mold. For fiberglass, do the same thing. Make your model from something that plaster won't stick to. Make a mold as described before. Now paint the inside with resin, let it set, then add resin mixed with fiberglass. You should be able to easily get walls of uniform thickness with no need for alignment.
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Very nice! I've had some experience with theatrical makeup, and this looks very similar to how foamed latex prosthesis are made. One thing puzzles me: what was the purpose of spraying the female mold with laquer?
Here's an approach that's closer to the foamed latex procedure: This should allow for better control over the thickness of the box's walls.
Make a negative of what will be the inside of the box. Avoid undercuts for obvious reasons. Cover this with wax and build it up to form what you want the outside of the box to be. Ladle a thin plaster over the negative, making sure there are no bubbles against it. Build up a layer of, say, 1cm. Then stick it into a box filled with plaster, as you did. Before you do this, bore at least three holes equidistant around the edge of the negative. Insert metal rods into these holes. When you put the inside negative into the plaster, the rods will stick into the wet plaster. These rods will remain in the plaster and slip out of the inside negative. When the plaster is cured, remove the inner negative and as much wax as you can. Put the plaster mold and inner negative into an oven on low to melt out the remaining wax. You will now have a pair of perfectly-fitted male and female molds. The metal rods will make sure the molds stay properly aligned.
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Am I too late to bump my order up from 36 to 50 SIFAM knobs?
CORE troubleshooting
in Testing/Troubleshooting
Posted
Whether or not to grind the tip depends on the type. Copper (with or without nickel plating) are supposed to be ground. Ironclad ones should never be ground.
I grind my tips by hand with a single-cut file. What do you press your tips against when grinding them in a drill?