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
>