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Re: sample clock playback tricks



> In a message dated 98-02-05 14:53:28 EST, Kim wrote:
> 
> << interesting problem, new technology comes along, making huge 
>improvements
>  in some ways and obsoleting the old stuff. But there's usually some
>  characteristic of the old stuff that becomes very difficult in the new
>  technology. And then you need a few more generations of new technology
>  before you are able to do the old idea again. In this case, you used to 
>be
>  able to easily change the sample clock on A/D and D/A convertors, and 
>they
>  would be happy and nothing else in a simple delay system would get 
>screwed
>  up. Nowadays, the convertors give better audio but don't let you do that
>  sample clock trick anymore, and other things in the system that need
>  accurate timing (like midi) get screwed up. So for the echoplex and 
>jamman,
>  this sort of thing is impossible. So now you need to add a fair amount 
>of
>  dsp processing and more sophisticated real-time os techniques to be 
>able to
>  do what once just required a very cheap part. such is progress....
> 
>  kim >>
> 
> Any idea how the Boomerang folks got around this problem, at least 
>insofar as
> their unit offers half speed/half sample rate playback?  Boomerang folks?

  The convertor we use offers a range of fixed sample rates
mathematically related to the frequency of the associated oscillator or
crystal. We have recently upgraded to a chip that offers more
flexibility. I believe the sample rate can be set to 1K, 2K, 3K... up to
the frequency of the driving oscillator. Another benefit of this chip is
that it is absolutely silent when switching between rates.
  As far as converters that are truely continuously variable in sample
rate... I don't know of one, but then I haven't done a survey of the
current technology; it changes rapidly.

Mike Nelson

Boomerang Musical Products
PO Box 541595
Dallas, TX 75354-1595

Tel       800-530-4699 (outside USA, 214-340-6913)
Fax       214-343-1038
email     mnelson@dmans.com
web page  http://www.boomerangmusic.com