Joined: Dec 26, 2006 Posts: 144 Location: United Kingdom
Posted: Sat Jan 19, 2008 4:26 pm Post subject:
Blue Hell wrote:
TheProf wrote:
[...]for wider bandwidth
The two PIC12 implementations you pointed to both run well above 20 kHz, would that not be fast enough?
An interesting modification might be to use an external voltage controlled clock generator on the PIC chips.
The algorithm's loop time is about linear with the length of the shift register. The sequence length however grows exponential with the length of the shift register. Meaning that you could have sequences that won't repeat in millions of years on a marginally more expensive micro controller.
I was thinking of getting at least 48KHz, so as to give a 'sample rate' above the audio range. I know, (and if I remember the math may be a bit nasty), that sampling theory might not quite apply to a filtered PRBS, but I would like to be certain. In my own case, I want to build a good accurate, (in terms of average amplitude stabilty and spectrum), audio white/pink noise generator, to do speaker lineup and level work. Without too much work, I might be able to get a good clean 440Hz out of the same widget.
On a parallel topic, I think electronica is one of the few areas wher many record companies don't digitally compress the hell out of recordings. I like my music with dynamics. I think I finally realised just how important they were after going to a live performance of Messian's 'Turagalila Symphony' at Manchester's Free Trade Hall, back in the 80's. I'd gone mainly to hear an actual Ondes Martenot. The dynamic range of the piece, (and no amplification bar that in the Ondes Martenot), blew me away. _________________ Mike
I also like the effect of some of the less optimal, shorter length sequencers. When you can hear the repeating.
Sure, me too
The shift register noise has some properties that analog noise doesn't have, and the other way around as well of course. _________________ Jan
also .. could someone please turn down the thermostat a bit.
Actually the faster one runs at 67 kHz or so, and the other just above 40 kHz. The 20 kHz or so number given in the source code for that 2nd one is wrong. It has 24 clock cycles in the loop and the processor runs at an instruction rate of about 1MHz.
When it has to do a sine as well you'll need a faster processor, but a square might just fit along with the noise in the 1st algorithm. The clock of the PIC12 is not very precise BTW, it runs on an internal RC and it has a factory set compensation register to get it at about 4MHz. Ther is some temperature dependency as well. You could connect an external xtal or clock generator though.
I'd love to see a played Ondes Martenot as well, once, heard some beautiful recordings of it.
About speaker line up, the last person who told me about how he was working on that said that he would do it with clicks, and would then use some software to analyze the results ... maybe subtracting the room response on the click ... it's too long ago, my memory fails on it _________________ Jan
also .. could someone please turn down the thermostat a bit.
Joined: Jan 18, 2007 Posts: 95 Location: Mark of the Dane
Audio files: 4
Posted: Sat Jan 19, 2008 5:23 pm Post subject:
I know this is getting off topic, but...
Blue Hell wrote:
I'd love to see a played Ondes Martenot as well, once, heard some beautiful recordings of it.
Care to name some of those recordings? I'd be interested in finding some, I've only (knowingly) heard this machine once...
TheProf wrote:
On a parallel topic, I think electronica is one of the few areas where many record companies don't digitally compress the hell out of recordings. I like my music with dynamics.
Wouldn't mind, but it was on the radio and many years ago and I probably do have some recordings of it on compact cassette if only I knew where ... my "sound memory" works way better than the "word memory" ... sorry.
Thanks Photon for the clip! _________________ Jan
also .. could someone please turn down the thermostat a bit.
My god that was amazing Photon, thanks! I've only seen Johnny Greenwood playing an Ondes and very short clips at that. I had no idea that it could be so varying and responsive to performance. It blows my mind that someone invented an electronic instrument almost a century ago that is so expressive, what I wouldn't give for a DIY Ondes!
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