"Self tuning piano" questions

[Isaac sur Noos]

Hello, very ingenious and certainly repeatable system.

That's funny this was my next question to ask if the pickup should be
able to energize the string !

Did you experiment this "overdrive" effect while the piano play ? It
could be a method to correct the sound of a piano, or to produce new
kind of tones ?

I doubt nowadays that it reproduce the phase coupling that the tuner
is initially after, did you experiment on that side of the process ?


I still don't understand if you use a tension reserve in the string to
bring it to pitch , or is the string warmed to correct pitch (that
induce changes in iH I guess, how much I don't know, but a 35 °string
is toning softer than a 20 ° one) .

Have you experienced for curiosity, on the spectra changes with the
heat ?


Best Regards.

Isaac

------------------------------------
Isaac OLEG
accordeur - reparateur - concert
oleg-i@noos.fr
19 rue Jules Ferry
94400 VITRY sur SEINE
tel: 033 01 47 18 06 98
fax: 33 01 47 18 06 90
mobile: 033 06 60 42 58 77
------------------------------------


> -----Message d'origine-----
> De : Don A. Gilmore [mailto:eromlignod@kc.rr.com]
> Envoyé : jeudi 25 décembre 2003 17:10
> À : oleg-i@noos.fr; Pianotech
> Objet : Re: "Self tuning piano" questions
>
>
> ----- Original Message -----
> From: "Isaac sur Noos" <oleg-i@noos.fr>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: Thursday, December 25, 2003 6:17 AM
> Subject: RE: "Self tuning piano" questions
>
> Merry Christmas, Mr. Oleg:
>
> > Don,
> >
> > While i did not get really the inside of the ^process, I
> understood
> > that you are able to measure pitch on a very short moment .
> >
> > Is the measure occurring as long as the system is on (and
> corrections
> > applied with heat all along ?)
>
> No.  The tuning process takes place only when the system is
> swiched on.  It
> takes about 30-60 seconds and then the tuning is maintained
> as long as the
> system is on.  In other words, the "in-tune" values of
> electrical current
> for each string are stored and then held constant to keep
> the piano in tune
> for that day's conditions.  The next time you turn on the
> system, you get a
> new, custom tuning.
>
> > Is the measure/pitch regulation occurring always at the
> same time, or
> > is it the fact that the initial tuning is recorded by the
> same process
> > that gives enough accuracy - the question is about the lack of
> > stability of pitch, if the measure occur only once, it should be
> > precisely at the same moment to be accurate.
>
> The strings are sustained magnetically at a specific,
> repeatable volume
> during the tuning process.  If you take the signal from the
> pickup coils,
> amplify it and then apply this signal to another coil, the
> latter coil will
> actually sustain the string as if drawing a violin bow
> across it.  This
> allows the system to tune without the user having to play
> any notes.  It
> also ensures that the string is always tuned at the same,
> constant volume.
> After the piano is tuned at the factory, this is the volume
> that the tuning
> is "recorded" at, so the tuning you get in your home will
> be very precisely
> duplicating that at the factory.
>
> > But I suppose it is a real time system is not it ?
> >
> > Why are the pickup not catching overtones (are they partials ?)
>
> Yes, by "overtones" I mean partials.  There are two reasons
> why I don't get
> overtones.
>
> 1.  Because the pickup is very small and cheap.  The
> larger, more complex
> and expensive a coil is, the more partials it can
> reproduce.  This is the
> goal in a guitar pickup.  But in our case, it behooves us
> to use a crappy
> pickup.
>
> 2.  Because the feedback circuit that sustains the string
> tends to want to
> only drive it at its fundamental.
>
> The combined effect of these factors means that the signal
> shows up on an
> oscilloscope as an almost perfect fundamental sine wave.
>
> Don A. Gilmore
> Mechanical Engineer
> Kansas City
>
>