[sdiy] Tap Tempo

[Scott Gravenhorst]

"D A F" <polaris30 at ncx.com> wrote:
>This might be a dumb idea but could it be done with a phase-locked loop =
>of some kind?  I dont recall them being used to track frequencies in the =
>single digit hertz range but could it be done?
>
>Dave

PLLs will respond that low easily, but they have no "memory".  Once the
tapping reference input ceases, the PLL's VCO will return to it's natural
free running frequency.

Memory is why this application is best left to digital, esp. microprocessor
circuits.  I would think that this is an easy job for a PIC.


>
>  ----- Original Message -----=20
>  From: Amos=20
>  To: Tim Parkhurst=20
>  Cc: D A F ; synth-diy at dropmix.xs4all.nl=20
>  Sent: Thursday, December 29, 2005 2:48 PM
>  Subject: Re: [sdiy] Tap Tempo
>
>
>  A simple tap-tempo program to feed to a micro is along the lines of:
>
>  begin program on first tap event -
>  measure time until second tap event
>  measure time between second and third tap events
>  average the two measured intervals
>  set the new tempo to be one beat =3D the average interval over the =
>three taps.
>  (and reset the counter so that the next tap initiates the cycle again)
>
>  so a-one, a-two, a-one two three and by the downbeat you are groovin' =
>in tempo.
>
>  This is how tap tempo in the moog MuRF is implemented... In practice I =
>find it works a bit better than the simpler method of taking only one =
>interval between any two taps - which is less accurate (or rather =
>requires the user to be more accurate).
>
>
>  On 12/29/05, Tim Parkhurst <tim.parkhurst at gmail.com> wrote:=20
>    This did come up a while ago (six months or so, I think), and the =
>general consensus was that a microprocessor-based solution would be =
>simpler and much more accurate. Well, simpler if you know how to program =
>a micro. I think a discrete digital solution ( i.e. not involving a =
>micro) was also proposed, but this would probably end up using a lot =
>more hardware than a processor driven solution. Might be worth checking =
>the archives.=20
>
>    And no, not really off-topic at all. :)
>
>
>    Tim (as simple as it gets) Servo
>    --=20
>    "Imagination is more important than knowledge." - Albert Einstein=20
>
>    ***************************
>    On 12/29/05, D A F <polaris30 at ncx.com> wrote:=20
>      Hi all,
>
>      sorry if this might be a little off-topic, but here goes:
>
>      I was wondering if anyone knows how the more recent effects with =
>"tap tempo"=20
>      (where the period of an LFO is synched automatically with the taps =
>from a
>      foot switch) is implemented?  Does this have to be done with a =
>processor of
>      some kind, or could it be done in analog?
>
>      thanks,
>
>      Dave
>
>
>
>
>
>
>
>
>

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