Strobe Tuners and accuracy

[Richard Moody]

An execellent description of the Conn Strobo tuner can be found in Wm
Braid White's  "Piano Tuning and Allied Arts" It is the twelve window one.
  Also interesting is how the modern one wheel model displays the first
seven or eight harmonics. Amazing how the 'stroboscopic" effect can make
sections of  same wheel appear to be going forward and backward at the
same time.  
	According to White it uses the principles of toothed gear wheels to
correspond to the ratios closest to the Equal Temperament ratio of twelth
root of 2.  The closest two ratios are 84/89, and 101/107.  so guess how
many teeth the two sets of driving gears and wheels have.  White claims
that the two ratios are off "slightly more than 1 cycle in 16,000, an
utterly negligible error."  He does not say the machine is that accurate,
and indeed his description raises many questions as to how accurate it can
only be within the confines of the electricial and mechanical variances.  
	Also his discussion raises questions about how the human understanding of
what the frequencies of pitch should actually be. Or how the accuracy of
ear should be evaluated by machine.   "By methods now to be described, it
has been found that, even with what is called good tuning, a systematic
error of more than 2 cents throughout five of the seven octaves of the
keyboar, is commonly detected."  p228.   He does not say how this two cent
"error" occurs but alludes to it by  saying, "This somewhat distressing
practical fact, together with others of parallel importance, has  been
brought out clearly for the first time since the pioneer work of Ellis,
done more than fifty years ago, was set forth in his appendices to his
monumental English edition of Helmholtz."  and he goes on to describe the
"ingeniously devised apparatus.... developed by the research engineers of
C. G. Conn, Ltd..."   This is as far as he goes about the "two cents
error".  and implies this is what was used to detect this error, but no
actual readings are given.  
	The "pioneer work" of Ellis I believe is White's reference to the
calculation of beat rates of all Equal Temp. intervals, esp thirds,
fifths, fourths, and sixths, from the partials.   Or maybe he was refering
to the discovery of partials sharp from theoretical.  Did Helmholtz know
that?  (Helmholtz is not sitting on my desk at the moment)   That could
lead to a 2 cent "error" from theoretical.  The machine was set up to
theoretical, but the partials being sharp, no wonder it detected a
"systematic error, throughout five octaves." IMHO. 

Richard Moody 
5-31-98
----------
> From: Robert Scott <rscott@wwnet.net>
> To: pianotech@ptg.org
> Subject: Strobe Tuners
> Date: Saturday, May 30, 1998 1:35 PM
> 
>
> 
> 
To me, the term "Strobe
> Tuner" implies a means of indicating a pitch by sampling the phase
> of the measured signal using a reference clock (or "strobe" signal).
> The two most common Strobe Tuners (Conn and Peterson) both use
> mechanical means to generate their pattern.  But the SAT is also a 
> Strobe Tuner.  Instead of using a mechanical wheel, it uses an
electronic
> simulation of a wheel.  .....

................
> 
> Robert Scott
> Detroit-Windsor Chapter, PTG