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Changing the delay time on a BBD

 
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Dub Attack Force



Joined: 24 Nov 2007
Posts: 31

PostPosted: Wed Dec 05, 2007 8:08 pm    Post subject: Changing the delay time on a BBD Reply with quote

Should be possible to do it just by replacing the clock/crystal don't you think?
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interruptor



Joined: 04 Sep 2005
Posts: 1138
Location: Switzerland

PostPosted: Thu Dec 06, 2007 12:22 am    Post subject: Reply with quote

sounds reasonable to me. i'm no specialist for analogue electronics though.. if you change the cristal make sure the other characteristics of the cristal (apart from frequency) are as similar as possible to the original.
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KoCha



Joined: 25 Jan 2002
Posts: 259
Location: Switzerland

PostPosted: Thu Dec 06, 2007 4:44 pm    Post subject: Reply with quote

Not a specialist too, but doesn't exist 'parametric' clock ?

Making you able to change delay time 'on demand'...

I remember having build little blinking led using a clock with a pot on it on electronic lesson...

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KoCha, reggae-dub producer

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Dub Attack Force



Joined: 24 Nov 2007
Posts: 31

PostPosted: Sat Dec 08, 2007 9:47 pm    Post subject: Reply with quote

Thanks guys. The variable clock idea based on a Hex Schmitt trigger or a 555 timer oscillator is an excellent idea. Although surely, we must be overlooking something and it can't be that simple or else someone would have done it already.. or would they? For the sake of reggae science someone should try it out.. I might give it a shot but I don't have the time at the moment. I love the wobbly sound of BBDs and that low hissing noise they make.

This is my one:

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Looter



Joined: 13 Mar 2001
Posts: 111
Location: US

PostPosted: Mon Dec 31, 2007 3:00 am    Post subject: Reply with quote

Aren't BBD chips just a series of capacitors? I think the only way to do it would be to connect two chips together in series.. I also have only rudimentery knowlege of electronics.
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Dub Attack Force



Joined: 24 Nov 2007
Posts: 31

PostPosted: Mon Dec 31, 2007 3:14 am    Post subject: Reply with quote

http://mysite.du.edu/~etuttle/electron/elect39.htm

For delays in the millisecond range, between the ranges where recording or wave propagation are convenient, the Bucket-Brigade Device (BBD) may be useful. This is an NMOS or PMOS VLSI (very-large-scale integration) device that is essentially an analog shift register. Analog values are shifted from one cell to another by clock pulses. At the input end, the band-limited signal is sampled at the clock rate, and at the other the sampled values are made available at a later time. Low-pass filtering then restores the band-limited analog signal. These devices were first used to read out the analog values of a CCD (charge-coupled device) optical sensor. A line of pixels is transferred to the units of a BBD, and then shifted out serially. It was recognized that these devices could also serve as delay lines, so BBD's were manufactured for this specific purpose. They have the very great advantage that the delay time can be varied simply and electrically by changing the clock frequency.
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KoCha



Joined: 25 Jan 2002
Posts: 259
Location: Switzerland

PostPosted: Thu Jan 03, 2008 10:33 am    Post subject: Reply with quote

Nice to learn that Dub Attack Force Very Happy
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