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nebula

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Posts posted by nebula

  2. please help before i give up :(

    in MIDIbox SID

    Posted

    Back in the day (like, mid-1980s) I actually managed to destroy a couple of 6581s by trying to connect them to a telephone line (for touchtone dialing).  After they were damaged, their output was much quieter, so you would need to severely boost the volume of your speakers, which of course drastically amplified the noise floor and made that "last sound sustaining forever" much, much more noticable.

    I suspect your 6581 is likely damaged in the same way.  You really need to try another SID.

  7. Buffering DOUT Triggers

    in MIDIbox SEQ

    Posted

    No matter what you use, you'll need one for each output.

    But ... how much are you out if you blow up a 74HC595 ... about a buck or so?  Is it worth it to add complexity to your circuit?

    If you decide to go the opto route, you're fully isolated, and I'm pretty sure I've seen arrays of at least 4 of 'em in a single (SMT) package.  There are definitely numerous ways to go about it, but I think optos are the best means of the type of isolation you're talking about, and aren't really that expensive compared to other ICs you could use.

    (Please somebody else stop me if I'm being completely stupid)

  11. The beginnings of a mbSID :)

    in MIDIbox SID

    Posted

    OK, first question. Will the following rotary encoders be able to be used on the mbSID?

    Theoretically any encoder that outputs quadrature, or "2-bit Gray code", should work.  The real question is whether the selected encoder is desirable or not - for many reasons.  If it looks good, it probably is good ... but you might consider sharing a link to its datasheet.

    They're needed for inputs (so that the switch connects the input to GND when no jack is inserted) but not for outputs.

    To clarify:  you can use a switched jack for an output, but you won't need to use the extra terminals.  Switched jacks are also often used for headphone outputs, when the signal is perhaps normally routed to an internal amplified speaker, and plugging something into the jack breaks that connection so that you only hear it through the headphones.

    Even the MB-6582 uses switched jacks on its outputs: when you don't plug something into an output jack, it gets passively mixed with the next output.

  12. I think I've done my homework...

    in MIDIbox HUIs

    Posted

    Good contact where I pulled the pad off. Whew, what a relief. I've got to reorder some pin headers, but I need more AIN and DIN modules anyway, so no big deal.

    Don't beat yourself up not soldering that header flush - it happens to everybody.  It doesn't take long to get good at soldering, but it can take a long time to get good at desoldering.  Many projects I have created have little wires running all over the boards, as I've made modifications, changed my mind about things, or pulled off a pad when I tried to remove something.  You can almost always fix it - it just might not always be pretty.

    Another question. How do I wire up panel mount midi jacks? Not an easy thing to search for around here as "midi" turns up in every post.

      Mount the jacks first.  Then you'll want to use stranded, insulated wire.  I like tinned copper, which shows a silvery colour once you strip off the insulation, but plain copper works as well.  You'll want anywhere from around 28 gauge to 22 gauge.  Strip about a centimetre off the wire, then push the stripped part through the eyelet of the terminal on the back of the jack. Then just wrap the rest of the bare wire around the terminal. Squeeze it a bit with needlenose pliers or tweezers if the wrap isn't nice and tight.

    You'll want your iron to be hotter than you would normally use for circuit board work.  If you don't have a temperature control, allow the iron to get really hot by sitting by itself without much air movement around it for a minute or two.  Hold the tip of your soldering iron on of the flat sides of the terminal for a moment - remember that the mission is to quickly transfer heat from your iron to the terminal, so if your soldering tip has a flat edge, or is a "screwdriver" style tip, you want to use the flat part of your iron against the flattest part of the terminal.

    Then apply your solder to the other side.  If it's hot enough, solder should immediately flow over the terminal.  Quickly remove your iron so that you don't melt any plastic parts of the jack. Let it get nice and hot again before working on the next terminal (if you don't have a high-powered iron, you just wicked away a lot of its heat with the relatively thick terminal, your wire, and the solder).

    If you can still see the outline of the indivdual strands of your wire after you're done, you probably didn't use quite enough solder.  You want to use just enough to fill between the strands, making the joint appear smooth, or almost smooth.  You don't need any more than that.

    BTW the exact same technique applies to almost any panel-mount part, including potentiometers.

  14. Starting New MB-6582 Build - Any Requests?

    in MIDIbox SID

    Posted

    Things that got me:

    If you don't already have some decent clamps, spend a few bucks and go buy a few.  Using crappy, ill-fitting clamps to secure the board to the panel during the JB-Weld process is more trouble than it's worth.

    I don't know if it's documented yet or not, but there's an electrolytic capacitor on the lower part of the base board that you might want to put on its side instead of straight up.  If you look at pics of most completed base boards, you'll see what I mean.  If you don't do this, it might get in the way when you try to put the case together.

    There are very important instructions in the construction guide to trim away a bit of the plastic on the top-right screwhole of the PT-10 ... make sure you pay attention to this (unlike me), or you will keep swearing (like me) as you try to put the front panel board into place and you end up bending the "SID R" LED.

    When buying tactile switches, you will have a choice of how much resistance they have.  This is expressed in "grams of force" or gf.  The standard choices are 100, 160, and 250 gf.  I used 160 gf buttons, and they're good, but I think I would have preferred 100.  My buttons are a little clickier than I would like them to be.  But that's just me being fussy - I still am really happy with the final product.  And if I get ambitious I could always swap 'em out, I suppose.

    I had a little piece of tinted anti-glare coating that I glued just inside the display window.  It adds a nice finishing touch.

    MB-6582 is an great sounding, very usable synth.  Its firmware is remarkably deep for a DIY synth, and it's truly fun to build.  Take your time and do a good job, because the boards really are beautiful.  If I didn't have a wife to answer to, I'd probably be building a second one!

  15. Looking for encoder with 16 detents

    in Parts Questions

    Posted

    I am trying to find encoders with exactly 16 detents per revolution for a good price.  I ordered an encoder from Digi-Key (Panasonic # EVE-QDBRL416B , digi-key # P12423-ND), which is "16 pulses per revolution", but I didn't realize that this actually means 32 detents.

    Does anybody have a suggestion as to where to look for an inexpensive 16-detent encoder?  The weird thing is that the one I got is only a few bucks from Digi-Key, and the ones that actually have 16 detents cost about 4 times as much.  I'm looking for 2-10 pieces, and I don't want to spend 10 bucks each.  Integrated pushbutton switch is optional.

    Thanks

  17. Do I really want SIDS?

    in MIDIbox SID

    Posted

    Even back when the C64 was current, I always thought a MIDI-controlled SID synth would be cool.  I always wanted something like that, and I drooled over the SIDstation, and planned on building a MIDIbox SID "one of these days..."

    Last year I finally built an MB-6582.  It exceeded my expectations in every way.  You can get wonderful sounds from a pair of 6582's.  Recognizing the original application of the SID, it is quirky compared to "professional" synths.  It is these quirks that make it sound different.  When I get a sound in my head and start programming the MB-6582, I usually find 5 great new sounds along the way.

    I'm still no expert on programming the thing, which is why I haven't shared anything yet.  The MB-SID firmware is remarkably deep and mature.  Honestly, it's a hell of a lot more than I bargained for.

    I think the real power of the MB-SID is in PWM and Oscillator Sync.  Like many synths, it can shimmer, and it can scream.  Like few synths, it can do both at the same time.  

    The white noise generator has a unique, grainy video-game quality to it which makes for interesting sound effects.  Interestingly, it can be played chromatically even when bypassing the filter.

    MB-SID's firmware control over AOUT is ingenious.  Along with an AOUT/AOUT_NG board, it can control a VCF such as Seppo's awesome little SSM2044 board - a sweet, aggressive-sounding filter, quite similar to a Polysix.  But you can pump any synth through the filter, and MB-SID will give you ADSR/LFO control over the filter, plus proper keyboard tracking.

    While it wouldn't be my first pick as the only synth in my setup, I'm starting to use my MB-6582 more and more.  I would recommend it to anybody with a little electronic experience, some time, and a few hundred bucks.  If you value your time more than tweakability, I would recommend the MB-6582 over the "individual modules" approach.

  19. Wanted: CEM3394

    in Fleamarket

    Posted

    Yeah, that seems to be the going *bay rate.  In the past hour I've actually found them individually from a local broker for less.  So I might be on the right track.

    As for help with the software:  I'll bet you could be a huge help.  But I think this is going to be my MIDIbox coding baptism.  Since I've shown up here I've built only a couple of things, and I haven't yet touched a line of code, so this will be my chance to make something cool.  Be forewarned: once I get going I'll probably be asking for general help here in the forum, including some nasty n00b questions, so go easy on me! ;)

  20. Wanted: CEM3394

    in Fleamarket

    Posted

    Thanks Stryd, but I've been planning to work on something 3394-based for a long time.  Now that I have AOUT working, I want to get busy!  My goal is to hack the MIDIbox SID code to work with the 3394.  In order to control multiple voices, I may still wait until MB-SID is mature on STM.  But even if only as spares for my Six-Trak, I'm ready to buy some 3394's now!

    The 3396 is the voice of the Matrix-6 / Matrix-1000 and the Cheetah MS-6, so you'll probably get some cool stuff out of that too.  It looks like one of the key differences is that the 3394 is controlled with voltages while the 3396 is primarily controlled digitally.

  22. Wanted: CEM3394

    in Fleamarket

    Posted

    Thanks prof - but they're not the same thing.

    CEM3372 = VCF

    CEM3394 = VCO, VCF, VCA in one IC ... used in some Sequential stuff from the period (Six-Trak, Max, Split-Eight, Multi-Trak), and also in the Akai AX60, some others ... it was also used in several video arcade games as I understand it.

  24. Wanted: CEM3394

    in Fleamarket

    Posted

    Wow, that is pricey.  Technology Transplant was selling them on eBay 6/$99, but seems to have just raised the price to 6/$149 (OUCH).

    These ICs appear to be remarkably easy to control ... did you know that the Sequential stuff (Six-Trak, Multi-Trak etc) uses only a single-channel DAC to control 6 of these buggers with no special s/h chips?

    I thought it might be fun to control some with an AOUT, but the price seems a little stupid.

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