Doepfer

Thanks Michael, yes, I was taking 100kHz as the max internal clock 
frequency. Doubling that gives higher octaves. Thanks for your reply 
and hopefully you can report back on your 256. I have decided on the 
512 pending further input.

Thanks,
Doug

--- In Doepfer_a100@yahoogroups.com, "Michael Wagner" 
<michael.wgnr@...> wrote:
>
> Hi Doug,
> 
> Definitely a late reply, sorry for that.
> I just received my 256-stage-BBD today,
> and couldn't yet test it, but I just tried to
> verify your claims. In theory, you've got the
> math right, but the manual of the BBD states
> the following:
> 
> "[the clock oscillator frequency] depends upon the BBD
> used in the module and is related to the max. clock
> frequency of the BBD in question (pls. refer to the table on
> page 3). It is about 250 kHz for BBDs with 2048 and 4096
> stages and about 450kHz for BBDs with 1024 stages and
> less (i.e. a bit more than the max. clock frequency of the
> specs in the data sheet)."
> 
> Furthermore, there is a table with the shortest available
> delay for each BBD. E.g. the 256-stage BBD would have,
> acording to its specification, 0.64ms minimum delay time,
> which translates to 1562.5 Hz, that is roughly a G6.
> 
> So, I hope that helps a bit; and also hope I got the details
> right.
> 
> -Michael
> 
> On Wed, Apr 30, 2008 at 6:01 AM, Doug <dougc356@...> wrote:
> > Hi folks, according to my calculations, the number of BBD stages 
is
> > related to the highest possible musical note via karplus strong
> > synthesis as follows:
> >
> > 128max=G5
> > 256max=G4
> > 512max=G3
> > 1024max=G2
> > 2048max=G1
> > 4096max=G0
> >
> > Am I wrong? Here's how I got there:
> >
> > 1) the frequency of the karplus strong loop is the note that 
will be
> > heard as the loop attenuates. This frequency F is equal to
> > F = Fs/N where Fs is the sampling rate and N is the number of 
samples.
> >
> > 2) According to the Doepfer documentation for the A-188-1, the 
design
> > clock range of these modules is roughly 10kHz to 100kHz. I am 
assuming
> > this is the range of acceptable values for Fs. So taking Fs as 
100kHz,
> > and N=128 (for the 128 stage BBD), the highest note that this 
setup
> > can play is
> > 100000Hz/128 = 781Hz or roughly a G5. The lowest note is not so 
much
> > an issue, but just for grins, 10000Hz/128= 78Hz, or roughly D#2.
> >
> > 3) For comparison, the 256 stage BBD will only manage 100000/256 
=
> > 390Hz, or about a G4. And it goes down an octave with each 
doubling of
> > the number of stages.
> >
> > Since it appears that my guitar roughly covers octaves 1 through 
4 (I
> > think) the 256 BBD is the ideal number of stages for plucked 
string
> > sounds.
> >
> > Any advice is appreciated, especially from those who have tried 
BBD
> > modules. Thanks, Doug
>