EFM takes a break - Re: modules with different tubes?

[tomg]

I swear it says "PV-1 Pitch to Voltage Converter By Harry" or something
like that..;-) right on the top of the page Harry, or it did which is why I'm
writing this.

Phil says they lost the usr HD and it could be a day or two before it comes
back up.....and then I have to re-up the files....so now we know.

We worked all weekend on the database and web-site. It's gonna be really 
nice...but now we have to wait to upload it. Anyway it gives me a day or two 
to reorganize things.

I still have 10meg at GC, so if I need to I can post something in the mean
time.....the address is here...........

http://www.geocities.com/efm_gc/


Tom





> Hi Scott...
> 
> The detector on TomG's site is the board I layed out based on Bob Moog's
> 
> Etherwave Pitch to Voltage Converter (with permission). It works well on
> any
> regular waveform, but needs to have the fundamental cleaned up a lot for
> guitar.
> (this depends on your expectations... I'm really fussy!)
> 
> I looked into the idea of using the Hilbert Transform. You need a "dome
> filter" also
> described in electronotes, I believe.  I got the info from JH's pitch
> shifter (frequencies only) and did a spice model of the filter. The
> problem is... there is enough group delay
> in the dome filter to wipe out the advantage of getting rid of the
> harmonics...  you will
> end up in the same place as the LPF anyway. That seemed like a great
> idea... and probably would work for high pitches.
> 
> The Gold patent assigned to New England Digital gives a workable method
> for
> guitar pitch extraction. It will not work well on voice at all...
> because it uses the facts that
> guitars are almost always decaying exponentially... and that the
> harmonics are...
> er.... non-harmonic.  Vocal harmonics would be much closer. Guitar
> harmonics are
>  very sharp!
> 
> H^) harry
> 
> Scott Bernardi wrote:
> 
> > You run into the same problem trying to do pitch to voltage
> > conversion. TomG has a pitch to voltage  converter on his site that I
> > seem to remember uses a downslope detector to detect the true
> > fundamental (his site seems to be down right now).
> > There's also an Electronotes article EN#136 that discusses using a
> > Hilbert Transform: take the signal and the 90 degree phase delay
> > network, square both of them with multipliers, then sum the squares.
> > It supposedly removes harmonics and strengthens the fundamental,
> > improving the multiple zero crossing problem of complex signals.  Then
> > he runs it into a downslope detector to extract the true fundamental.
> > I plan on playing with it (sometime - you know how it goes) because I
> > want to build a pitch to CV I can use with voice or guitar.
> >
> > harry wrote:
> >
> >> Aahhh....
> >>
> >> Nice try. Probably will not work.
> >>
> >> Problem... How do you decide the "waveform" crossing points.  I'm
> >> thinking of
> >> a Guitar wave... which is a bastard !  It may cross zero more times
> >> than you
> >> like.
> >> Tracking the peaks will not work either.
> >>
> >> DDL  pitch shifters do exactly this. If they have very short
> >> delays... the
> >> glitches in
> >> the waveform are severe. If you can wait a week... you could make a
> >> really long
> >> delay.
> >>
> >> You should tape record the whole thing... then edit out every other
> >> cycle, then
> >> play
> >> at 1/2 speed...
> >>
> >> Or just hire a Psychic to set the unit properly for the "next" note
> >> you are
> >> about to
> >> play....
> >>
> >> H^) harry
> >>
> >> Magnus Danielson wrote:
> >>
> >>
> >> > From: harry <harrybissell at prodigy.net>
> >> > Subject: Re: modules with different tubes?
> >> > Date: Sat, 13 Jan 2001 11:44:39 -0500
> >> >
> >> >
> >> >>  If ANYONE gets a really good octave divider for guitar, tube or
> >> >>  otherwise,
> >> >>  LET ME KNOW !!!
> >> >>
> >> >>  I'll build it even if it is TUBES....  ;^)
> >> >>
> >> >>  (of course I doubt anyone will ....)
> >> >>
> >> > Hmm... I just came up with an obscure idea using a pair of BBDs,
> >> > but
> >> > I am sure you're not interested ;)
> >> >
> >> > Theory: Do frequency tracking, fetch an overtone to sample in a
> >> > full
> >> > BBD, play it out at half clock-rate. Alternate BBD so that one is
> >> > in
> >> > "record" and the other is in "play" mode. Since they track
> >> > frequency
> >> > one snaps a waveform and plays that pitched down but on the same
> >> > boundary. Simple? Heck no! Obscure? You bet!
> >> >
> >> > Reason for concepti!
> >> >  on? Annoyment and ammusement of Harry! ;)
> >> >
> >> > There are loads of problems with this strategy thought. Can we
> >> > learn
> >> > anything?
> >> >
> >> > Cheers,
> >> > Magnus
> >> >
> > --
> > Scott Bernardi
> > sbernardi at home.net
> >
> >
>