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