Downsizing Verilog synthesization.

eromlignod wrote:
> On Aug 9, 6:09 pm, Jim Granville <no.s...@designtools.maps.co.nz>
> wrote:
> 
>>Hmm... has this been proven on a working unit, in the field ?
>>
>>Better would be a system that can _prove_ what you stated, by
>>tracking the frequency even during a performance. It does not
>>have to adjust, but knowing just how many ppm the thing
>>has drifted, would seem a strong selling point
>>
>>-jg
> 
> This would be difficult since no song ever plays all 88 notes.  In
> fact the top and bottom few notes may never get played (I am a pianist
> myself and have never seen music written for A0 or C8).  And if a note
> is played too quickly, like with staccato, there may not be enough
> clean vibrations to get an average.
> 
> There is also the fact that a note's pitch changes slightly with
> volume.  A louder note sounds a little sharp since there is more
> string excursion and thus more tension.  My system magnetically
> sustains each string at a steady, repeatable volume, which is the same
> volume it is sustained at when the tuning is "recorded".
> 
> The whole idea of the system is to get a fresh tuning in a few seconds
> on a daily basis.  Every time you press that button, you could have
> spent $100 and over a hour of inconvenience.

  Understood, but I am talking about making something that is both
calibration/control system (when you push the button), and a
measuring instrument (when playing).
  Sure, playing is dynamic, but you are not making control decisions,
just checking the calibrations.
  Think of it as a seriously precise spectrum plot :)

  Is this a one-off, of do you hope to sell a number of these
commercially (or seil the one-off to someone else, who will
production-engineer it ?)

-jg

Jim Granville wrote:
(snip, I wrote)

>> Putting analog PLL frequency multipliers on each string would be
>> interesting, but take a lot of extra circuitry.  I don't know
>> DLL enough to say, but it might work.  I would read up on
>> DLL (that is, the digital version of the analog PLL).

> Why add more jitter/noise ? In my example, a low 1Mhz timebase
> reciprocal counter is 63 TIMES more accurate than the OP's
> 15.9mHz spec - so it has 6 extra bits of precision.
> (500KHz would be my trade-off target)

Yes, I was thinking about running it continuously,
or at least close.

> On a more practical note, I can't see a stored-cal approach
> working very well (too much thermal drifing about..)

I agree.

-- glen

On Aug 11, 1:49=A0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> Yes, I was thinking about running it continuously,
> or at least close.
>
> > On a more practical note, I can't see a stored-cal approach
> > working very well (too much thermal drifing about..)
>
> I agree.
>
> -- glen


Making the tuning accuracy too fine is a waste of time.  I have found
that a string naturally fluctuates in pitch by up to a tenth of a cent
or more, even if it is being resonantly sustained.

I have also let a string be maintained at a constant PWM for up to
three days with no measurable change in pitch.  Maintaining the string
at a constant temperature is basically the same as an ordinary piano
sitting at room temperature.  Gradual changes in humidity are by far
the largest factor in causing a piano to go out of tune anyway.

Don
Kansas City

eromlignod wrote:
> On Aug 11, 1:49 pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> 
>>Yes, I was thinking about running it continuously,
>>or at least close.
>>
>>
>>>On a more practical note, I can't see a stored-cal approach
>>>working very well (too much thermal drifing about..)
>>
>>I agree.
>>
>>-- glen
> 
> Making the tuning accuracy too fine is a waste of time. 

Not to an engineer ;)

> I have found
> that a string naturally fluctuates in pitch by up to a tenth of a cent
> or more, even if it is being resonantly sustained.

but how do you know if that variation is the resonance changing, or your 
measurement noise floor ?

<paste>
 > I need an accuracy of
 > less than one "cent" (1/100th of a musical semitone).  One cent sharp
 > at 27.5 Hz is
 > 27.5 * (2**(1/1200)) = 27.5159 Hz

So that's ~477ppm, and the one tenth you mention is 47ppm - and that has 
to be close to the noise floor of sense of a single note (14+ bits),
(expect rather worse measurement floor on 44 notes all at once!)


> I have also let a string be maintained at a constant PWM for up to
> three days with no measurable change in pitch.  Maintaining the string
> at a constant temperature is basically the same as an ordinary piano
> sitting at room temperature. 

Almost : It depends on your total power budget, needed for your thermal 
expansion tuning. All that 'abnormal' heat is going to spread slowly, 
and also dry things out - so you will have a lot of time constants
in a working system.

How many watts does this typically drain, when running ?

Coefficent of thermal expansion of the range of strings ?
(steel is ~11-13ppm/'C)

-jg

On Aug 11, 4:27=A0pm, Jim Granville <no.s...@designtools.maps.co.nz>
wrote:
> > Making the tuning accuracy too fine is a waste of time.
>
> Not to an engineer ;)


I am an engineer with 22 years' experience (UMR 1986).  I also studied
piano at the UMKC Consevatory of Music for sixteen years, starting in
1972.



> > I have found
> > that a string naturally fluctuates in pitch by up to a tenth of a cent
> > or more, even if it is being resonantly sustained.
>
> but how do you know if that variation is the resonance changing, or your
> measurement noise floor ?


Believe me, I have extensively researched pitch and tuning, with help
from the Piano Technicians Guild (of which I am a member) and the ME
department of the University of Wichita.  Counting a 50 MHz clock
gives me much more accuracy than is needed.


> So that's ~477ppm, and the one tenth you mention is 47ppm - and that has
> to be close to the noise floor of sense of a single note (14+ bits),
> (expect rather worse measurement floor on 44 notes all at once!)
>
> > I have also let a string be maintained at a constant PWM for up to
> > three days with no measurable change in pitch. =A0Maintaining the strin=
g
> > at a constant temperature is basically the same as an ordinary piano
> > sitting at room temperature.
>
> Almost : It depends on your total power budget, needed for your thermal
> expansion tuning. All that 'abnormal' heat is going to spread slowly,
> and also dry things out - so you will have a lot of time constants
> in a working system.
>
> How many watts does this typically drain, when running ?


Power consumption is a function of tuning range and how far each
string is out of tune.  A study was done at the University of
Washington where it was proven that a piano varies in pitch cyclically
by less than 20 cents (total runout, worst string) throughout each
year (it was a 3-1/2-year study).  So I am aiming at a tuning range of
about 30 cents to start out with.  This would take about 750 watts if
every single string were the entire 30 cents out of tune (sharp).

Don
Kansas City

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
> My thought was stepper motors on each tuning peg.  (Small and
> geared down a lot.)

Gibson makes a robotic self-tuning guitar that works this way I believe.

G.