Strobe Tuners

[Robert Scott]

Bill Bremmer writes:

>Any kind of Strobe Tuner is inadequate for tuning a piano.  It does not
>provide the right information and is not nearly sensitive enough. 

If, by "Strobe Tuner", we mean a tuning device that does not have any 
stretch (all octave fundamental ratios are 2:1), then I quite agree
that such devices are inadequate for professional tuning.

However, there is nothing in the meaning of "Strobe Tuners" generally
that require that they have no stretch.  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.  Instead of sampling the phase with a flashing neon
light, the SAT samples the measured signal using electronic "gates" to
take an electronic snapshot of the measured signal where the reference
signal controls the "shutter".  But the effect is the same.  The pattern
of lights in the SAT indicates the phase difference between the measured
signal and the internally generated reference.  Of course, the SAT is
also more sophisticated inthat it uses a bandpass filter to focus on one
selected partial, and it uses a custom stretch calculation for the
reference frequency for every note.  But there is no difference in 
sensitivity between a common Strobe Tuner and an SAT.  Both devices 
display one complete cycle of pattern movement for one beat between
the measured signal and the reference signal.

In theory, one could make a mechanical wheel strobe tuner with
bandpass filtering to select partials and FAC-type stretch.  In fact
there is one advantage such a device would have over its digital
cousins.  An mechanical strobe wheel displays infinitely many phase
positions as the pattern smoothly rotates.  Digital displays have
discrete steps.  Now it is true that the SAT simulates a continuous
display using the fact that the lights can have varying brightness.
But this is not quite the same thing as having a visual pattern 
that moves continuously.  I remember talking with the people at
Peterson Electro-products several years ago about updating their
mechanical strobe tuner to an all-digital product.  (Note: At that
time Peterson was targetting their products more to organ builders
than to piano tuners.)  Their thinking at the time was that the
continuous nature of the mechanical strobe wheel was too valuable
to give up.

Robert Scott
Detroit-Windsor Chapter, PTG