Theo Verelst Diary Page

Latest: 3 April 1999

I've decided after good example to write some diary pages with toughts and events.

Oh, in case anybody fails to understand, I'd like to remind them that these pages are copyrighted, and
that everything found here may not be redistributed in any other way then over this direct link
without my prior consent. That includes familiy, christianity, and other cheats. The simple reason is
that it may well by that some people have been ill informed because they've spread illegal 'copies'
of my materials even with modifications. Apart from my moral judgement, that is illegal, and will be
treated as such by me. Make as many references to these pages as you like, make hardcopies, but only of the
whole page, including the html-references, and without changing a iota or tittel...

And if not? I won't hesitate to use legal means to correct wrong that may be done otherwise. And I
am serious. I usually am. I'm not sure I could get 'attempt to grave emotional assault' out of it, but
infrigement on copyright rules is serious enough. And Jesus called upon us to respect the authorities of
state, so christians would of course never do such a thing. Lying, imagine that.

Previous Diary Entries

29 March 1999

There's a little gap in the continuity of the diary, I have no computer at home (I think I'll take one there soon, at least to experiment with the webcam, anyone out there with 'creative' webphone software ?), and I've been busy.

The balloon I've been talking about has already many flying hours! Got myself 4000 liters of helium, and latex balloons up to a meter and half in size, and at about 80 centimeters diagonal, they fly nicely, even with the radio control receiver and a single servo attached to it. I'l put up some pictures (I have to get them from the gallery computer), and since I can now digitize video, I' consider putting on some video as well. I've also experimented with the propellor and a small motor to give the mini-airship some thrust, and that works better than I thought, 1 (rechargeable) battery, with a minor current, making it last for many hours, makes the balloon carrying it move at walking speed easily. Next step is to make it manouverable, I think two 80cm balloons together will carry the motor the remote control, and the height control unit. I need more channels on my remote control (2 channels for about $60 is not bad anyway), so I took it apart, and figured out the servo control is standard: 1 to 2 mS pulses, spaced 20 mS apart, HC logic will drive a servo nicely, and a control signal was made with only two (out of six) schmitt triggers from a 74HC14 inhalf an hour or so:

the led signifies how much pulse comes out, putting a 1k resistor in series with the potmeter to trim it, makes the whole range just right for the servo I used. Next step: make a speed control for the propellor motor with a power fet.

Also, the second amp is in the making, same enclosure, different knob layout (it doesn't need as many), and it gets more industrial (repeatable layout and parts), but not as much as it can be. Tomorrow I can get some more amplifier IC's of the type I already used, they can supply only three at once, I want 6 at least (to tri-amp both stereo channels)... They're cheapthough, and pretty good. I tried a simple butterworth (no spell check to help here) 2d order to seperate the latest reasonably high quality woofer, and that seemed to give a lot tighter bass response. Of course I'l also hook up the 24 dB/oct voltage controled filter for testing, that produced some very hefty bass sounds on the previous speaker, but is probably not up to my real high Q audio standards. Any standard filter will give very serious phase distortion over quite a range of the pass spectrum, that may only be compensatable by assuming a flat response of the speakers in the cross over range, and averaging out the phase differences by good orthogonality of the filters, I don't know wether that theoretically is possible, I'll do my math some day (Or pick up some physics book), and see wether such a filter is physically feasible. This would also require that the way the speakers interact with the ear is exactly phase-coherent, which is feasible for the woofer/squaker (and subsquacker, which in my latest experiments for high Q and high power seem desirable), but hardly for the tweeter: any angle outside the plane in the mid-plane of equal distance between the twoo (or even three, depending on the steepness of the filter and the broadness of the pass band) will give significant phase differences in the centimeter wave range, thus cancelling and amplifying frequencies around the takeover point.

That's a general prob, does Tannoy sell those little woofers-and-tweeters-on-one-axis as parts? It would be a good speaker idea to
fit all cones on one axis, use one magnet to drive-em all, maybe, anyhow, that in high quality seems like a good product. The alternative is to make the takeover range so small that is is hardly noticeable, in the order 1/100 of an octave or so, with phase constant filtering, which in practice can be done only by a serious DSP in high resolution and good programming, like piecewise fft-ing or wavelett transformations or an (equivalent or adapted) high order 'custom' filter, anyhow with seriously long sample and thus delay times. There is a system like that, with measurement results on impulse response and spatial frequency spread to fall in love with... Very expensive, though, and I didn't hear it yet. Oh, and he, ever tried to do small or medium scale PA amplification with a fixed 100mS (or so) delay in the MAIN channel?!?! Not nice.

On a differently fundamental side of technical 'things', I've started a text on the basics of digital electronics (will define the term), that should be readable by anyone who has serious interest in the fundamentals of computer stuff that have remained fairly unchanged over the last few decades, and who can connect a light and switch to work. It is the kind of thing that got me going from the age 11 onward or so, and there is nothing much around that deals with the subjects that in my mind are more relevant than screwing a network card in a computer without having a clue as to what actually goes on in the circuits. I'm aiming at the knowledge that made me understand (with time) what computers or lets say at least digital electronics that make alarm systems work, are realy made of, knowledge that hasn't even started to become obsolete yet, and in fact seems to have gained relevance for those wanting to do something practical with cheap and understandable parts, instead of hooking up to one of the so many suppliers of digital half-products without ever getting close to the core of things.

I'm not sure what exactly I will do with it, but have a look at this link, and let me know what you think, it might make a nice book. I did a part of the design of a folder (for the gallery) the last few days, its good to put those G3's to work and get a profi looking printout with almost brillian photoshop-ed pictures. Didn't try a photo printout yet with the 'quarkexpress' layout program that appears to be used by glossy mags as well, but direct from photoshop that makes for pretty good artwork, just a bit low on specifically special colours, for instance I tried to scan a books cover and print that out with good quality, but I just couldn't crank out the exact deep red colour, the Espon (photo) couldn't do that just right. Fun enough though to have 600dpi or so in pretty real full colour pixels interactively available on a system, even at A4 or A3 format when desired.

I've been using an hour or two spare time on the latest amplifier while writing this as well, and have done some video shooting of the work, I already have a digital movie of it now, but that runs in the few dozen megabite range, so I'm looking for some video software to cut and edit it, hopefully with decent audio editing as well. As soon as I have movie well under a meg, i'll put it on.

The front panel.

Adjusting a light to do digital photos of paintings while secretly being recorded, and the balloons in the back, one quite shrunk because Espen couldn't resist to spay paint eyes and teeth on it...

Amp building.

Supply test: I light a few (60W, 60 Volts) lamps with the amplifier supply, and let them dim slowly because of the capacitors in the supply unit.

Paul (Blanca) doing fridge stuff, and a decent new bike (formerly a rental, like the previous one I used to bike from Delft to Amsterdam with several times)

Meet the new product! How many would you like?

I recently wanted to use this as the front page for an inside extra paper, as a demo, but was asked to use less daring one, pity, the processed version of it looked real good, it is made at a house party some weeks ago, where they modeled for life painting. The second one is on the same night, ltr Marie-Louise and Steffi. The last one took quite some processing to recover.
These ones:

were taken on request of the subjects: mail me for a print (or digi version)! The latter two needed a lot of processing, I should have flashed them, too.

I'll do some piano stuff as well, but the piano in the gallery is at an exposition, its' a painted over grand, owned and done by Herman Brood (the 'saterday night' one, I think it was a hit in the US as well years ago) whom he made available, so I currently feel musically challenged, all the more since coming sunday I'll do some band playing again after quite some time.

Most this has nothing much to do with inner thoughts, and some of the things and people I think about daily, and the 'whole of things', to put it straight. A recent email I wrote has more to do with that, I'll quote it, hoping it may be of some use, the addressee is american, so it luckily is in english.

April 3, 1999

I owe you the email, and the 'book' link, I'll put them on later.

I got myself a stereo sys today! The last few days I took some time to gather some more parts and do a decent mechanical design of a 2x100Watts amp with a neat enclosure (the one above), and solder the whole thing together. In fact I don't think too much of making a thing like that, in fact i did a 2x70w amp in a neat case in highschool some 15 years ago already, albeit in a wooden case, and with inferior specs to this one, but then again, I didn't have $8 parts with a nice mosfet amp in them available, I had to built it with discrete transistors. My point is just that its nice to do a professional and fairly heavy dusy case, and take up the challenge to make the think in an industrial-like manner, i.e. to the point, sensible, and repeatable.

All that aside, I just hooked up the two speakers I have pictures of on my pages, ade a direct lead to a serious cd player, opened up the volume, and I my first serious hifi experience since a long time. Sigh. First some relatively lousy modernistic cd where stereo images are limited to some detuned sample smeared around the picture, but earth wind and fire cracked it: there were drums in position, carefully played yet strong bass lines, voices that actually live, yep, that's how it should more or less be like. I don't doubt that later on I will pick on the shortcomings (the seperation filters, for one thing, and one speakeris probably a bit of-standard as well), but the first impression is nice. It's in the gallery, so more testing later on. Oh, I didn't get it anywhere near clipping (though it should clip relatively nicely: its a fet output stage) levels yet, but got pretty loud while hardy noticing, which is a good sign, too.

Saw the printers' folder pre-prints of the flyer I worked on: good enough to make 60 thousand of, I think, I'l put up a sample. Now I have the chance to do a brochure for my own to-be company as well, and in fact I may already have a serious employee, too...

April 5, 1999

Have a look at my model airship page, it flies! More later.