TheAncientOne

Have you though of spliiting the work over 2 or more regulators? If part of the current is for LED's etc, then they aren't that critical, and you can use the expensive precision regulators for your cores. I did an industrial control panel where about 40 LED's were fed from their own variable voltage regulator, so they could be adjusted in brightness to cope with summer days and winter nights. A decently big silicon diode will drop about 0.7V, rising with current. for example, a 1N5400 series diode will drop 1 volt at it's rated 3Amps. There is a problem here though: at 3 Amps 1 Volt drop, the diode will be getting rid of 3 Watts of heat. Tjmax for one of these is 170oC, and case to air thermal resistance is 53oC/W, meaning that at 3 Amps and an ambient temp of 20oC, the junction will start to overheat. (53x3 + 20 > 170), So I'd use a much higher rated diode. A 1N5821 Schottky Diode will drop about 0.5V at 3A, and will only have to lose 1.5W. Doing the same sums, with Tjmax125oC, and thermal resistance 28oC/W, gives a reasonable margin, (28x1.5 + 20 = 72 << 125), though you could split the load over 2 diodes for safety. (I showed the 'wrong' case to illustrate the pitfalls). Hope this helps Mike

In that case he's going to have to call it "SID Barrett". Mike

Ok, I've had another look at the diagram, and since I can't get any AD633's for 2 weeks, I'll let you have my 'best guess' at the wiring. The switch is a double pole, double throw toggle. Using Marc's circuit pin-outs, arrange it so that in multiplier mode, Pin 1 connects to pin 2, and pin 4 connects to pin 3. In divide mode, Pin 1 connects to pin 3 and pin 4 connects to pin 5. That's why there are only fives wires to six terminal on the switch. Looking at the back of a normal DPDT switch, (the "o's" rrepresenting switch pins), we would have: [tt] 2 o o 3 1 o o 4 3 o o 5 [/tt] I can't guarantee that this is right, but I'm fairly certain. The data sheet at http://www.analog.com/UploadedFiles/Data_Sheets/AD633.pdf shows the divide circuit on page 5. Pretty cool doing you're own PCB's: I've never been too good at it. Hope this helps Mike

Way back at the end of the 80's I rescued a church organ project where the local guy, a retired organ builder had fallen ill with about 80% of an organ functional. The ranks and actions were in, as was the core wiring, but he'd not actually started the stops boards, due to lack of parish funds. They had a nice 2 manual and pedalboard system, (recycled), hard wired to a limited range of stops. I had to tread diplomatically on this one, but we had a local who worked for Hewlett Packard, and he came up with an HP 150 Touch screen computer, running (I think), DOS 3. There was a good FORTH for the 150, so I wrote a touch controlled stops system, using the same type of layout as used on the dealing room autodiallers. We could have 32 stops per page, and I think we used 2 pages to fit in all the other bits. HP150's used HP-IB, and we used the this, via some HP data-slector modules, (from Computer test systems), to interface the box to the organ. I did it in such a way as not to interfere with his wiring. The final version had user selectable coupler/pistion actins, and ways to group up pages of stops and remember them. It booted off one floppy, and had another for data storage. It was supposed to last for six months of so until he was back on his feet. It ran for over 3 years in the end, though is now replaced with lovely classical stops, with electric action, (it's cool to press 'general cancel' and watch them all jump back in at once). The HP touch screen used escape sequences and could be programmed with them too, for terminal type systems. There was a C API, but the FORTH was fast enough and for me, more flexible. I wrote my own escape sequence words, and built up from there. I can still remember doing the lists of stop names, with the old guy 'directing' in a funny and irascible style. The only problem we had was dust in the IR sensors on the original 150. If I had used a 150/2 then this wouldn't have been a problem, because HP fixed it. I did a big stack of boot discs, just in case they lost any. That old HP stuff was built to last, and the only service call I had, once debugged, was to change the batteries. My favourite memory is getting impromptu lessons in tuning pipes, since he couldn't go scrambling around inside the works and I remember getting a faceful of dust from the first time the 16 foot open flutes had sounded for ages - they're very loud at close range too. The reason I'm getting to, is that a lot of POS (point of sale systems) use touch panels too, usually over LCD's, so this might be a good starting point. The outputs of the older ones are serial, and simply return a postion and an on/off as an ASCII string. Modern ones all seem to be USB, with driver only for PC's. I love electronics, and working with it, but sometimes I do get this hankering after rooms full of wood and metal, with esoteric names. Sorry for the long winded post, a bit of a reminisce, if you want to talk touchscreens, you could memo. Mike

Well you could just build the Roman Sowa version at: http://www.sowa.synth.net/modular/rm.html I'll have ago myself and see if I can hack the divide switching, It's just a DPDT switch, but I'm not quite sure enough of my analysis to talk without testing. I note that in the changeover state the op-amp is left open loop as the switch goes over, which should make for an interesting noise! I have to jack it together and see. Marc Bareille's PCB's are quite good, and whilst not in the MIDIbox range of value, are still, in my opinion, quite good. Mike

Oakley have a new 303 style sound module design just released: the TM3030. http://www.oakleysound.com/tm3030.htm I've ordered one - it cost 42UKP, for the board, pot bracket, pre programmed processor and a tempco resistor, (which I always find hard to get). The Ladyada design looks great, but it's above my price limit at the moment, though considering all the tracing of obsolete parts that went in to it, I guess about £200 delivered to the UK is pretty good. One of my friends is pushing me to clone him a Synergy. At first it was a flat 'No!', but then I got thinking about their digital oscillator and FPGA, and we're at 'Just maybe'. It would be a hell of a lot of work, but I can remember when the Bell labs GDS was in the literature originally, and lusted after one terribly. The docs say the last version of the Synergy was an improved GDS. The original Synergy 'core' ran on a Z80 with 16K RAM and 32K EPROM..... It's probably almost as powerful as a MIDIbox SID.....

This looks interesting - I've never used the Fairchild opto's - I'll get some myself. I can see one initial problem on page 4 of the data sheet, Fig. 4. The device seems quite temperature sensitive, so some kind of servo loop. such as you describe, might be needed. I used an analogue version of this for the outputs of an ECG amplifier, sadly it was a long time ago and I don't think I've kept the notes. No: I am not a relative of Fermat...... Best wishes Mike

I tried this once as a way of getting PWM --> CV. The repsonse time of vactrols and similar is strange - the response and recovery times are not always symmetrical and both a relatively slow. I'd say fast enough for LFO type work, but not fast enough for FM. A coast through the data sheet at: http://optoelectronics.perkinelmer.com/content/DataSheets/DTS_OpticalIsolators.pdf will fill in the details. You willl notice that the faster VTL series have Ton and Toff times are in the 1mSec upwards region, limiting your PWM rate, the cheaper LT series being in the 10mSec upwards category - more for control isolation. HTH Mike edited to add: the application note: http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_AnalogOpticalIsolatorsVACTROLS.pdf is useful too.

There are two I have worked with - shown here. If you don't fancy the soldering, the Entec bare board kit is very good. Their pro versions provide isolation between the controller and the DMX, which is a useful safety feature sometimes. There is quite a lot of open source lighting control stuff out there too, though I'll leave you and that nice Mr Google to find it. One of my early reasons for looking at MIDIbox was to do a lighting desk to interface to a PC based DMX controller, though the reason for that isn't pressing now, so I'm more concerned with the music side at the moment. http://www.usbdmx.com/usb_dmx_interface.html http://www.enttec.com/index.php?main_menu=Products&prod=70303&show=description&name=opendmxusb Hope this helps. Mike

Rapid in the UK have 24LC64 for £0.62 plus VAT and Carriage http://www.rapidonline.com/productinfo.aspx?kw=24lc64&tier1=Electronic+Components&tier2=Micros+%26+Crystals&tier3=Memory&tier4=Serial+EEPROMs&moduleno=35151 They have a lot of other useful stock too. Otherwise I could put some on my next order and do you a swap for something. Hope this helps Mike

The hardware interface can be SPI, so that wouldn't be a problem. The difficulty, as audiocommander points out, is that you would have to implement a file system for MIOS. Most USB sticks use FAT which is strictly a non-trivial task, and would probably eat up more of the core memory space than your applications. Remember, down here in the real time controller world, 64K is a lot. In the PC world, it's buffer/scratch space. The FTDI stuff is good - one of the best DIY USB <-> DMX units uses one of their modules. I think we're talking horses for courses here - if you need to archive that much data then you do need a PC. If you're gigging, then how about building yourself a rackmount machine with an LCD screen, or recycling an old laptop? Best wishes Mike

Thanks very much for including the Pelog, Stryd. Did you find the Neil Ardley? Best wishes Mike

Vocoders can be monsters! Analog ones can be very versatile and give a good range of effects, but a big job to make, and do require fairly skilled setting up/tuning to sound good. Need a lot of close tolerance parts for good filters too. Digital ones eat a lot of CPU, if you want real-time. If you want to be able to do all the fancy patching stuff, then you may have to write your own code. No microcontroller can get into the speed range yet, so it's DSP or, if you fancy something very up-to-date, a custom processor running on an FPGA - ther are a couple of designs out on the web somewhere: http://www56.homepage.villanova.edu/scott.sawyer/fpga/II_freq_domain.htm this article is interesting. The frustrating thing about doing research for a musical vocoder is the amount of telecoms stuff you find, since they are the major users of the technique, and the telecom stuff isn't much use for music. The Elektor analogue design is still out there, and is a good one too - I built two for local musicians back when it was current, A little work could bring the design well up to date. You can download the original PDF's from the magazine site I think, and there are other versins on line too. Elektor and ETI design here, under 'synths' http://www.timewind.se/ There are quite a few soft vocoders available, some for free, though all need a PC. CSound has a phase vocoder with which you can 'morph' sounds. Csound has a very steep learning curve, I found, if you are a programmer, then it will be a lot easier. Just a few thoughts Mike

This data sheet is NOT the right one, but does give a few examples. I've used these in Point of Sale terminal work, and whilst there does seem to be a wide range of devices, they tended to use similar command sets. The I2C ones could be more varied. http://www.bipom.com/lcds/manuals/vk202-25.pdf If a couple of your IO pins are equivalent to RTS and CTS, then linking them together might be a start on finding out which are RXD and TXD. It will have to use some kind of flow control. It can be a hard slog working through all the permutations of baud rate, start and stop bits and pinout. Been there, done that, and if you look closely at the picture on the T-shirt...... Long shot: have you any info on the equipment they came out of? That might at least cut down the connection problems. At least you can use long simple leads on stage with them Quite a cool idea, an electronic cue sheet/set list. Now I suppose you could always do a text to speech for the drummer. Mike

Dear Sasha This is what you need - and there are PDF's on the page with notes on the operation of BCD and some circuits. The unit is made in Poland, so might be a bit lighter on carriage. http://www.chd-el.cz/index.php?id=312&lngid=en It is a 'full deal' controller too, unlike the rather basic Kenton. It even has a VCF output for filter sweeps. I don't know how 142 euro sounds to you - it doesn't seem a lot to me for what they are selling. I'll have to get sorted on my puzzle buying! HTH Mike

Hmmm - counting the blocks, the top ones seem to be 20x2's Mike

I've been thinking a lot about filter banks recently, and since I'm not a graphics wiz like Artesia, I'll have to describe my thoughts instead. I imagine a 19" rack cardframe with slots for 8 single filters or 8 pairs, (16), and some kind of routing along the lines Artesia shows. There are some many interesting designs out there, and none are that complex or expensive (until you build a lot!). From the MS20 variants to the Polivox, the Steiner-Parker, Moogs, Ken Stone and Ray Wilsons designs, not to mention things like the wonderfully gnarly wasp, and the CEM variants. I'd probably try to make pairs, but have them available for normal modular VC work as well. By judicious use of backplane connectors, it should be possible to get the right voltages to the right place, and to electronically lock out/lock down the front panel controls that we want to remote control, by a suitable signal from the control surface. The next thought was to tie this in with a variant on the MIDIbox 64e, with 8 pairs of LEDring controls, and some indicator lighted routing buttons. That way, with a bit of bankstick memory, the 64 could act as freqency and in some cases resonance controls for the filter stack, and the more direct control voltages could be mixed in as needed. With the right software on the end, all control input could be recorded - a bit like the way one can 'play the knobs' on Rebirth. This is definitely a bit too much in one go, but I like the thought of combining the units in this way, and still having them available for other work as needed. Having the Controller on another 19" panel, aligning with the filter bank might be quite good. A cool option would be to have LCD 'scribble strips' to label the controls, though that might take a bit of working out, even with some cheap LCD's, though at least the LEDrings wouldn't be needed then. A last idea might be to put some I2C EEPROM in the filter modules, like a distributed bankstick, and allow each filter to hold it's own settings, this wouldn't be used in 'stand alone' mode. A few rather random ideas..... Best wishes Mike

Hi Stryd I dug out the Keyboard IO card and did a rough pin check. This might be enough for a start. The cable seems to be a 25 pin straight through as far as I can see, so far. I finally weakened and unearthed the keyboard tonight, (hence the edit). You'll need to open yours over a sheet of newspaper or something - it's got the same crumbly foam around the key edges as under a Moog MG1 control panel. I didn't and my table is covered in sticky foam debris. It seems to be scanned in groups of eight and has a single wire per key, moving between a pair of bus bars, which indicates that it is velocity sensative. The bus bars are in eight pairs. It's scanned from the host - there is no on-board intelligence. The two 1/4" jack sockets are for pedals, they may be velocity sensitive too - they are on stereo jacks. Key isolation is by germanium diode, possibly a worry about volt drop. Keyboard electronics is a 74154 and two 74367's I'll beep out the circuits if I get a bit more time, but it looks to me like a simple I/O could be hooked to the existing circuitry. I've not got a full sized keyboard myself, so perhaps there might be a bit of a joint project here. Since a list of Apple IO pins is not exactly MIDIbox relevent, I've sent you them as a memo. Note this was earlier, and is just the Apple 2 end card. Hope it's some use - I'd always rather make an add-on than butcher rarities. I do know the keyboard cards for the Syntauri are rare, though I seem to remember seeing another one in one of the boxes. I've just found a whole load of cards I coiuldn't remember getting either. Apple Z80 card... now where did that come from? so there is hope. You'll need to keep a lookout for the Mountain hardware thingy - it's two Apple cards hardwired together with a ribbon cable, with flying lead phono connectors, and if you're lucky, a light pen. I'm in the UK, so a swap might be a problem - though if I find the other IO card, it might be cheap to mail you that, if you fancy trying a resurrection, (though more like necromancy I think!). Best wishes Mike

Did some more checking this weekend. The end result is this: Use 2 bridge rectifiers with two seperate secondaries Use one bridge with a centre tapped secondary. The diagrams at: http://www.tonmeister.ca/main/textbook/img600.png and http://www.musicfromouterspace.com/analogsynth/powersupply.html Are both good. The schematic at http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf is OK if you only have a single secondary winding and need plus and minus voltages. It won't suply as much current as a centre tapped secondary, because it's only half wave rectifying the AC for each regulator. Once I can get up to speed on something that will let me make decent schematics for the web, I'll try and do a proper write up. Mike

Hi Stryd Just noticed this: I've got a complete Alpha here, all bar a keyboard cable.....you didn't get a cable with it, did you? If you want to try ressurrecting the beast, I could probably dig out the interface card and trace it, it was only a little thing, as I recall. A Goth friend of mine tracked the software down for me last year. I think I've been putting off an attempt at a rebuild in case it sounds awful. I always fancied one of these 'poor mans Fairlights' when they were current. Now all I need for a complete set is a Greengate DS3, (remember "19" anyone?). Best wishes Mike

There are some nice FM tones in this video of Thorsten's:

Purely from personal experience, but if you are making a small scale audio device, switching power supplies are often more trouble than they are worth. 1) The output a lot of electrical background noise, which can be hard to keep out of the audio. 2) They often need a minimum load to work properly. 3) Cheap ones can suffer catastrophic failures and take out the equipment they are connected to. 4) Some of the cheap ones produce voltage 'spikes' on start up, which can damage your audio gear or ears. 5) They are an 'experts only' job to work on or repair: they can kill you, and/or your test equipment. For anything MIDIbox, so far, I think linears are best, unless you have a gazillion LED's in your control surface . . . Mike

I was referring to the pictures in TK's post. The http://www.ucapps.de/mbhp/mbhp_opl3_psu.pdf is the one I think is wrong. If you follow the diode path in TK's right hand drawing you'll see what I mean. I'm working away this weekend, when I get home I'll proto it up and check to make sure. This is a good circuit:http://www.musicfromouterspace.com/analogsynth/powersupply.html Basic thing is: you only need one bridge! Mike

I tend to the "In case of emergency, fit a vactrol", solution. You might have to do a lot of curve 'linearising', but at least the response speed won't be an issue on the resonance pot, unless you're planning some majorly weird patch. http://www.pacer.co.uk/product_details.aspx?companyProduct_id=141 Are the UK stockists, they have a reasonable minimum order cost of £15 plus VAT, and will take telephone orders. HTH Mike

There is a problem with the diagram. If you look at the right hand drawing, the middle two diodes in the left hand side of the are effectively back to back, thus connecting the centre tap to the ground, with a drop of about 0.7V, AC. Worse, if you look at the right hand pair, when the lower winding is positive, (and thus the upper one negative), they are in series across the windings, effectively shorting them out! If you have a centre tapped secondary, use 1 bridge, AC1 and AC2 to the outer leads, and connect the centre tap to ground. If you have two seperate secondaries, (or two seperate tramsformers), connect a bridge to each, and then common a positive and a negative to ground. HELP! what is a decent free or cheap program I can use to jot down quick circuit diagrams ? I've had a go in eagle, but I need more practice... Hope this helps Mike