[sdiy] LFO, analog computers

[danial stocks]

>Speakers: Anything you can carry allone will drop of @ 50Hz,
>radiation resistance of a speaker cone gets simply imaginary there,
>so not much power output, but lots of heating and membrane
>displacement. There was once a 80cm Woofer by Fostex, but even that
>won't do. A horn speaker for such low frequencys is incredible
>large. Perhaps piston?

someone told me about a site with online speaker/ box design equations, dont 
have the url anymore unfortunately.. a design they did with a C/V 18" driver 
and folded horn apparently was like a medium size pa bin and had fairly 
constant/useful iumpedance/sensitivity down to around 10-12Hz.. below that 
usually use servo motors/piston arrangement.. you could prolly make one from 
old stepper motor and a bit of Pvc conduit pipe.. another idea I heard of 
was like the heterodyning technique, but the high freq drivers were enclosed 
in opposite ends of a long pipe.. the sub audio radiates out a hole in the 
middle..

>:::> 2) Can capacitors be made by doping silicon, as chips are? I'm 
>thinking, if
>they
>:::> can be, a whole lot of sample and holds might be possible to make a 
>sort of
>an
>:::> analog hardrive; think : one capacitor the equivalent 32(64...) bits 
>of
>data.
>there, but different. Instead of charging a cap you shoot electrons
>into oxide. EEPROM or FLASH technology. The SAN corporation proposed
>256 level storage in 1996 for their FLASH and predicted the end of hard
>disk drives...
>
ISD chipcorders are analog eeprom.. nonvolatile storage/sampling in analog 
mode.. the early ones 16 seconds had 128K cells.. now they make ones with 8 
minutes or more ...that would be on the order of 3-4 million analog memory 
cells!!
OTOH, BBD's etc do leak out ie caps inside discharge if not clocked quickly, 
static rams style thing built of sample holds etc will not last long most 
prolly.. note that most long term s/h chips need an ext cap
Cheers,
Dan
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