pitchlock

[Carl Meyer]

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HTML MessageI may have found another use for pitchlock.

I have a 1923 Sohmer 5'4" cupid grand.  I rescaled it using pscale.

The sound of  A2 note 25 was what I'll call nasty.  I've heard this =
sound many times
and have never managed to fix it.  I had no clue what caused it.  =
Voicing had no effect.  Basically it sounds like a fairly high pitch =
twang (partial) that appears abruptly when starting at very low and =
gradually increasing the volume.  A tuner friend checked the piano and =
when I pointed out what I thought was a nasty note, he said "Yes, I hear =
what you mean but if you hadn't said anything I wouldn't have noticed =
it".  Another said "There are other notes that sound worse".  I think he =
was talking about a different kind of worse.

I finally thought maybe it was a longitudinal problem and I don't know =
what that even sounds like.

The pitchlock clips I had were too small so I fashioned one out of a =
piece of piano wire, put it on the bichord about a quarter inch from the =
bridge and the nasty sound was gone, gone, gone.

If anyone has the formula for longitudinal vibration interference, =
here's the data:
Note is A2, speaking length is 1017mm, core is .041, wrap is size 30 =
(.014) and exposed core is 12.7mm (1/2 in) at both ends.

I have had plans for building a device to find out the frequency of an =
offending sound through using a tunable filter and a tight fitting head =
phone floating around in the dark crevices of my kidneys for some time.  =
I guess now is the time to pass it.

Thanks guys for any comments.

Carl Meyer PTG assoc
Santa Clara, Ca.

=20



  ----- Original Message -----=20
  From: David Ilvedson=20
  To: caut@ptg.org ; pianotech@ptg.org=20
  Sent: Monday, October 03, 2005 8:05 AM
  Subject: pitchlock


  List,



  Sometime ago I was complaining about a new Pleyel upright with at =
least 8 mismatched bi-chord bass strings.   I could'nt get a clean =
unison and the octaves were impossible.  A few weeks ago I installed =
some pitchlock clips to the offending bass strings and voila...much =
better unisons and octaves.   I was going to change the bass strings...  =
Definitely worth keeping in the tool kit.



  David I.



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