Theo Verelst Local Diary Page 68

I've ditched the usual header for the moment, I think it doesn't help much anyhow.
This page is copyrighted by me, and may be read and transferred by any means only as a whole and including the references to me. I guess that's normal, the writer can chose that of course, maybe Ill make some creative commons stuff one day, of course I have made Free and Open Source software and even hardware designs available!

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  19 Feb, 2009

That's quick again! ´Watch High Definition´

Possibly from Vimeo:

I made this video already some time ago, some frames are here.

Fortune from Wed Mar 11 14:33:36 CET 2009:
Man usually avoids attributing cleverness to somebody else -- unless it
is an enemy.
-- Albert Einstein

The blues about synths?

A German (or Austrian?) site about  synthesizers

I was playing live TV from the server machine on one mplayer (Star Wars), and a DVD with another.

There are some great sound files from more than a few classic synthesizers, too, very worth listening to.

From the Dx-7 here are some great sound examples.

My tx802, well not mne, is on youtube:

Mobile phone power


I tested a scripting language on mobile phone.

Amplifier supplies in motion

Are your amps any good? Yep, the same chips are used by Velleman kits claiming high end hifi. Probably my pre amp and of course I multi-amp is better. My supply for the main amp seems though in spite of being much more powerful, to have less capacitance on it than this machine. I think this one has 40,000 micro farad per channel, wheras my main channels have only 10,000 per side. However, the toroid transformer responsible responsible for keeping those op to voltage every mains cycle, in my case is twice as heavy. And my wiring is probably, too. And of course in my case stereo has a shared tranformer per speaker group, I have 3 separate groups, with separate transformers and supply capacitors each, and in fact counting the rear biamped system, there is yet another complete supply. A quick computations teaches that my main amp would have a 7 volt ripple at 5 amp loading current.

It does have a 86 volt (2x43V with 10,000 uF) supply though, so relatively speaking that is not extreme. The supply rejection ratio of the chip is 80dB(V/V) IIRC, which is pretty good, presuming a good preamp can be important.

For the sub-amp, which is bridge loaded with 8 Ohms (500 Watt max. 15 inch speaker), the 2200uF at 76 Volts will probably dip quite a bit a high power, but only symmetric, and the speaker loads (with large enclosure) probably has only limited current peaks, and the shortest wave (a maximum of 40 Hz ()forty, no typo output) will take more than one recharge cycle.

Six million dollar man on Blu-Ray

That´s a question! Not a statment...

I looked up they used 35 mm film to film it in the early 70s I remember, so it should be possible I think to have a bluray instead of DVD box set to view them freshly anew!

Sign your name on the dotted petition line !

Bessel Functions

I found those first, I remember well, when snooping (well, dragging, but I tried hard to feel like snooping) around the Electrical Engineering faculty (it was already in that time) library, which was a whole floor on the tall building early 70s (late 60s?) style building with a good view on what used to be the Architectural design faculty at the time, but which has now burned to the ground.

I found them because I searched in High Frequency Electronics books after a mathematical modeling of the spectrum of Frequency Modulation,  like in FM radio transmission.

So I knew in lets say ´85 or ´86 what my FM synthesizer, the Yamaha DX-7 when using one modulator and one FM carrier operator would create audio spectrum-wise with changing modulation index.

More than one modulator is harder, and a chain of modulators too.

Currently, in the light of my string simulator, I want a good spectrum analysis of FM effects, but not with integer multiples of the fundamentals spectral components, but a continuous spectrum to look at and use for back transformation in time or string excitation domain.

Considering I´ve done more than a little working at theoretical physics, and am concerned about astrophysics (big bang and all) being too much of an estimate only, but not about the physics (and mathematical) part of that deal, I use some theory stated in that corner of the science universe, like here:


What does this mean? Well it´s about how the mass of a spiralling milky way (like ours, or other visible ones) holds together, including ´dark matter´.

Live Music In San Francisco

Interior improvement

Improvement all the time, Theo ? Well, at times, and of course when I'm not perfectly satisfied, I try to improve what I can such as local acoustics where I listen to my self built system, in this case in 6x4 concrete space. Hard concrete, luckily, though front and back walls are hopelessly resonating by themselves. Probably for small speaker effects, but that's not good, so I put major amounts of damping in to listen to my great speakers an amps.

For the first time, except for above the movie screen, I've added isolation to the (concrete) ceiling, and some nice lamps which I could now use again here:

Also I added some more to the sides, and actually made some mor space free on a side too, to get some natural reverberation:

The varied damping plates are a bit organized, but some of the setup is still a bit randomized, so no special reflection modes are emphesized. The ceiling is about 24 sq. meter, about 11 of them are now covered by standard carbon like surface curved foam, which doesn't really act as lets say protection of the neighbours from major sound waves. It does do some of that, though:

The plate of rather solid polyester crum (about 4 cm thick) shown here:

is able to do that, especially if that would be applied to the ceiling in a covering way. I wanted that, and have luckily enough for that, but I wanted a free standing frame to do it with, and it seemed only now the wood necessary appears again as available in a thin enough form to cover 4 meters with, so I didn't do that.

The plate there in the corner is quite needed because it is the corner opposite to the 15 inch sub-woofer where a lot of waves in the low range tend to resonate, but with the plate and the rest of the damping a whole lot less. To make the window in the door not resonate something should still be done...

This plate is above the beamer on the ceiling (don't mind my grainy processing, every picture is used to try something else out!):

Basically I didn't turn the concrete into cheese-with-holes by using only a number of nice white small hooks with 5 mm plugs, using a hammer-drill (a good one, actually) whichi works great, certainly compared with using a traditional drill with drill-with-hammering, which in this concrete is hopeless: 5 minutes per hole, and no more than a few cm in! This drill with click-mechanism takes 10 seconds for the 3 or so plug length cm.

The new plant (fairly cheap, but nice) is doing well:

I got a little very cheap conrad water pump, which has been put in this bowl:

Humidity is quite low.